Basics of the Defense Common Defensive Planning Considerations Forms of the Defense Fighting Positions Engagement Area Development Transitions   Introduction
    A defensive task is a task conducted to defeat an enemy attack, gain time, economize forces, and develop conditions favorable for offensive or stability tasks. (Refer to ADRP 3-90for more information.) Normally, the defense alone cannot achieve a decision. However, it can set conditions for a counteroffensive or counterattack that enables Army forces to regain the initiative. Other reasons for conducting defensive tasks include, retain decisive terrain or deny a vital area to the enemy, attrition or fix the enemy as a prelude to the offense, counter surprise action by the enemy, or to increase the enemy’s vulnerability by forcing the enemy commander to concentrate subordinate forces. This chapter covers basics of the defense, common defensive planning considerations, forms of the defense, engagement area development, and transitions.
  2. *****BASIC OF THE DEFENSE*****

    Basics of the Defense
    Key Points
    Characteristics of the Defense Defensive Tasks Order of Events Common Defensive Control Measures Sequence of the Defense Priority of Work Coordination Security Remount Point   Introduction
    3-1. The Infantry platoon and squad uses the defense to occupy and prepare positions and mass the effects of direct fires on likely avenues of approach or mobility corridors. While the offense is the most decisive type of combat operation, the defense is the stronger type. The following paragraphs discuss the basics of the defense.
    Note. Mission, enemy, terrain and weather, troops and support available, time available and civil considerations (METT-TC) determine the characteristics, placement, movement and maneuver of defensive positions.
  3. --Characteristics of the Defense

    3-2. The defense shares the following characteristics: preparation, security, disruption, massed effects, flexibility, maneuver, and operations in-depth. (Refer to ADRP 3-90 for more information).
    Soldiers engage enemy combatants.
    3-3. The defense has inherent strengths. The defender arrives in the area of operation before the attacker and uses the available time to prepare. These preparations multiply the defense’s effectiveness. Preparations end only when the defenders retrograde or begin to fight. Until then, preparations are continuous. Preparations in-depth continues, even as the close fight begins.
    3-4. Security helps deceive the enemy as to friendly locations, strengths, and weaknesses. It also inhibits or defeat enemy reconnaissance. Security measures provide early warning and disrupt enemy attacks early and continuously.
    3-5. Defenders disrupt attackers’ tempo and synchronization with actions designed to prevent them from massing combat power. Disruptive actions attempt to unhinge the enemy’s preparations and, ultimately, his attacks. Methods include defeating or misdirecting enemy reconnaissance forces, breaking up his formations, isolating his units, and attacking or disrupting his systems.
    3-6. Defenders seek to mass the effects of overwhelming combat power where they choose and shift it to support the decisive operation. To obtain an advantage at decisive points, defenders economize and accept risk in some areas; retain and, when necessary, reconstitute a reserve; and maneuver to gain local superiority at the point of decision. Unit leaders accept risk in some areas to mass effects elsewhere. Obstacles, security forces, and fires can assist in reducing risk.
    3-7. The defense requires flexible plans. Planning focuses on preparation in-depth, use of reserves, and ability to shift the main effort. Leaders add flexibility by designating supplementary positions, designing counterattack plans, and preparing to counterattack.
    3-8. Maneuver allows the defender to take full advantage of area of operation and to mass and concentrate when desirable. Maneuver, through movement in combination with fire, allows the defender to achieve a position of advantage over the enemy to accomplish the mission. It also encompasses defensive actions such as security and support area operations.
    3-9. Simultaneous application of combat power throughout the area of operation improves the chances for success while minimizing friendly casualties. Quick, violent, and simultaneous action throughout the depth of the defender’s area of operation can hurt, confuse, and even paralyze an enemy force just as it is most exposed and vulnerable. Such actions weaken the enemy’s will and do not allow all early enemy successes to build the confidence of the enemy’s Soldiers and leaders. In-depth planning prevents the enemy from gaining momentum in the attack. Synchronization of decisive, shaping, and sustaining operations facilitates mission success.
    Watch the following video to learn more about preparing for an enemy attack.
  4. --Defensive Tasks

    3-10. There are three basic defensive tasks: area defense, mobile, and retrograde. Each contains elements of the others, and usually contains both static and dynamic aspects. Infantry platoons serve as the primary maneuver element, or terrain-controlling units for the Infantry company. They can defend area of operation, positions; serve as a security force or reserve as part of the Infantry company’s coordinated defense. (Refer to FM 3-90-1 for more information.)
    3-11. As part of a defense, the Infantry platoon can defend, delay, withdraw, counterattack, and perform security tasks. The Infantry platoon usually defends, as part of the Infantry rifle company’s defense in the main battle area. It conducts the defense to achieve one or more of the following ─
    Gain time. Retain essential terrain. Support other operations. Preoccupy the enemy in one area while friendly forces attack in another. Wear down enemy forces at a rapid rate while reinforcing friendly operations.  
    3-12. An area defense concentrates on denying enemy forces access to designated terrain for a specific time rather than destroying the enemy outright. The focus is on retaining terrain where the bulk of the defending force positions itself in mutually supporting positions and controls the terrain between positions. The defeat mechanism is fires into engagement area, which reserve units can supplement. The leader uses the reserve force to reinforce fires, add depth, block penetrations, restore positions, counterattack to destroy enemy forces, and seize the initiative.
    Soldier stands ready to defend.
    Organization of Forces
    3-13. The leader organizes the defending force to accomplish information collection, reconnaissance operations; security; main battle area; reserve; and sustainment missions. The leader has the option of defending forward or defending in-depth. When the leader defends forward within an area of operation, the force is organized so most of available combat power is committed early in the defensive effort. To accomplish this, the leader may deploy forces forward or plan counterattacks well forward in the main battle area or even beyond the main battle area. If the leader has the option of conducting a defense in-depth, security forces and forward main battle area elements are used to identify, define, and control the depth of the enemy’s main effort while holding off secondary thrusts. This allows the leader to conserve combat power, strengthen the reserve, and better resource the counterattack.
    3-14. The leader balances the need to create a strong security force to shape the battle with the resulting diversion of combat power from the main body’s decisive operation. The leader usually allocates security forces to provide early warning and protect those forces, systems, and locations necessary to conduct the decisive operation from unexpected enemy contact.
    Soldiers provide security as a convoy passes through a valley in southern Wardak Province, Afghanistan.
    Main Battle Area
    3-15. The leader builds the decisive operation around identified decisive points, such as key terrain or high-payoff targets. The leader positions the echelon main body within the main battle area where the leader wants to conduct the decisive operation. The leader organizes the main body to halt, defeat, and ultimately destroy attacking enemy forces. The majority of the main body deploys into prepared defensive positions within the main battle area.
    3-16. The reserve is not a committed force. The leader can assign it a wide variety of tasks on its commitment, and it must be prepared to perform other missions. In certain situations, it may become necessary to commit the reserve to restore the integrity of the defense by blocking an enemy penetration or reinforcing fires into an engagement area.
    3-17. The sustainment mission in an area defense requires a careful balance between establishing forward supply stocks of petroleum, oil, and lubricants (POL); barrier materiel; and ammunition in adequate amounts to support defending units and having too many supplies located in forward locations that they cannot be rapidly moved in reacting to enemy advances. All suitable POL, barrier materiel, construction equipment, and laborers can be lawfully obtained from the civil infrastructure reducing the defending unit’s transportation requirements. Likewise, maintenance and medical support with their associated repair parts and medical supplies also must be forward deployed.
    Forms of Defensive Maneuver
    3-18. Two forms of defensive maneuver within an area defense are defense in-depth and forward defense. The Infantry platoon is expected to be able to do both. While the Infantry company commander usually selects the type of area defense to use, the higher commander often defines the general defensive scheme for the Infantry company. The specific mission may impose constraints such as time, security, and retention of certain areas that are significant factors in determining how the Infantry company will defend.
    Defense In-Depth
    3-19. Defense in-depth reduces the risk of the attacking enemy quickly penetrating the defense. The enemy is unable to exploit a penetration because of additional defensive positions employed in-depth. (See figure 3-1.) The in-depth defense provides more space and time to defeat the enemy attack.
    Figure 3-1. Platoon defense in-depth.
    3-20. The Infantry platoon uses a defense in-depth when ─
    The mission allows the Infantry platoon to fight throughout the depth of the areas of operations. The terrain does not favor a defense well forward, and better defensible terrain is available deeper in the areas of operations. Sufficient depth is available in the areas operations. Cover and concealment forward in the areas of operations is limited. Weapons of mass destruction may be used. Forward Defense
    3-21. The intent of a forward defense is to prevent enemy penetration of the defense. (See figure 3-2.) Due to lack of depth, a forward defense is least preferred. The Infantry platoon deploys the majority of its combat power into forward defensive positions near the forward edge of the battle area. While the Infantry company may lack depth, the platoon and squads must build depth into the defense at their levels. The leader fights to retain the forward position, and may conduct counterattacks against enemy penetrations, or to destroy enemy forces in forward engagement area. Often, counterattacks are planned forward of the forward edge of the battle area to defeat the enemy.
    3-22. The Infantry platoon uses a forward defense when ─
    Terrain forward in the areas of operations favors the defense. Strong existing natural or man-made obstacles, such as river or a rail lines, are located forward in areas of operations. The assigned area of operations lacks depth due to location of the area or facility to be protected. Cover and concealment in rear portions of the areas of operations is limited. Directed by higher headquarters to retain or initially control forward terrain. Figure 3-2. Platoon forward defense.
    3-23. Mobile defense is a defensive task that concentrates on destruction or defeat of the enemy through a decisive attack by a striking force. Mobile defenses focus on defeating or destroying the enemy by allowing enemy forces to advance to a point where they are exposed to a decisive counterattack by the striking force. The leader uses the fixing force to hold attacking enemy in position, to help channel attacking enemy forces into ambush areas, to retain areas from which to launch the striking force. Mobile defenses require an area of operation of considerable depth. The leader must able to shape the battlefield, causing an enemy to overextend its lines of communication, expose its flanks, and dissipate its combat power. Likewise, the leader must be able to move friendly forces around and behind the enemy force targeted to cut off and destroyed. Divisions or larger formations normally execute mobile defenses. However, the platoon may participate as part of the fixing force or the striking force.
    Note. Units smaller than a division usually do not conduct a mobile defense because of inability to fight multiple engagements throughout the width, depth, and height of their area of operation, while simultaneously resourcing the striking, fixing, and reserve forces. Typically, the striking force in a mobile defense consists of one-half to two-thirds of the defender’s combat power.
    3-24. Infantry platoons’ missions in a mobile defense are similar to missions in area defense and offensive missions. They are either a part of the fixing force or part of the striking force, not both. As part of the fixing force, platoons defend within their assigned area of operation, although the area of operation might be larger than usual. As part of the striking force, Infantry platoons plan, rehearse, and execute offensive tasks.
    3-25. Platoons use the term “striking force” rather than the term “reserve” because “reserve” indicates an uncommitted force. The striking force is a committed force that has the resources to conduct a decisive counterattack as part of the mobile defense. The striking force decisively engages the enemy as it becomes exposed in attempts to overcome the fixing force. The striking force normally attacks a moving enemy force, normally armor heavy.
    3-26. Retrograde is a defensive task involving organized movement away from the enemy. The enemy may force a retrograde or the leader may execute it voluntarily. In either case, the higher commander of the force executing the operation must approve retrograding.
    3-27. Retrogrades are conducted to improve a tactical situation or preventing a worse situation from developing. Platoons usually conduct retrogrades as part of a larger force but may conduct independent retrogrades (withdrawal) as required. Retrograde operations can accomplish the following ─
    Resist, exhaust, and defeat enemy forces. Draw the enemy into an unfavorable situation. Avoid contact in undesirable conditions. Gain time. Disengage a force from battle for use elsewhere for other missions. Reposition forces, shorten lines of communication, or conform to movements of other friendly units. Secure favorable terrain. 3-28. The three forms of retrograde are ─
    Delay. Withdrawal. Retirement. Delay
    3-29. Delays allow units to trade space for time, avoiding decisive engagement and safeguard its forces. Ability of a force to trade space for time requires depth within the area of operation assigned to the delaying force. The amount of depth required depends on several factors, including the ─
    Amount of time to be gained. Relative combat power of friendly and enemy forces. Relative mobility of forces. Nature of terrain. Ability to shape areas of operations with obstacles and fires. Degree of acceptable risk. 3-30. Delays succeed by forcing the enemy to concentrate forces to fight through a series of defensive positions. Delays must offer a continued threat of serious opposition, forcing the enemy to repeatedly deploy and maneuver. Delaying forces displace to subsequent positions before the enemy is able to concentrate sufficient resources to decisively engage and defeat delaying forces in current positions. The length of time a force can remain in position without facing danger of becoming decisively engaged is primarily a function of relative combat power, METT-TC and weather. Delays gain time to ─
    Allow friendly forces to establish a defense. Cover withdrawing forces. Protect friendly force’s flanks. Allow friendly forces to counterattack. Parameters of the Delay
    3-31. Parameters of the delay are specified in the order for a delay mission. First, leaders direct one of two alternatives: delay within the area of operation or delay forward of a specified line or terrain feature for a specified time. The second parameter in the order must specify acceptable risk. Acceptable risk ranges from accepting decisive engagement in an attempt to hold terrain for a given time maintaining integrity of the delaying force. The order must specify whether the delaying force may use the entire area of operation or must delay from specific battle positions. A delay using the entire area of operation is preferable, but a delay from specific positions may be required to coordinate two or more units.
    Alternate or Successive Positions
    3-32. Leaders normally assign subordinate units contiguous area of operation that are deeper than they are wide. Leaders use obstacles, fires, and movement throughout the depth of assigned area of operation. If the leader plans the delay to only last a short time or the area of operation’s depth is limited, delaying units may be forced to fight from a single set of positions. If the leader expects the delay to last for longer periods, or sufficient depth is available, delaying units may delay from either alternate or successive positions.
    3-33. In both techniques, delaying forces normally reconnoiter subsequent positions before occupying them if possible, and post guides on one or two subsequent positions. Additionally, in executing both techniques, it is critical the delaying force maintains contact with the enemy between delay positions. Advantages and disadvantages of the two techniques are summarized in table 3-1.
    Table 3-1. Advantages and disadvantages of delay techniques
    3-34. The alternate position technique normally is preferred when adequate forces are available and areas of operation have sufficient depth. Delays from alternate positions, two or more units in a single area of operation occupy delaying positions in-depth. (See figure 3-3.) As the first unit engages the enemy, the second occupies the next position in-depth and prepares to assume responsibility for the operation. The first force disengages and passes around or through the second force. It then moves to the next position and prepares to re-engage the enemy while the second force takes up the fight.
    Watch the following video to learn more about Delays from alternate positions.
    VIDEO -  Figure 3-3. Delay from alternate positions
    3-35. Delays from subsequent positions are used when assigned area of operation are so wide available forces cannot occupy more than a single tier of positions. (See figure 3-4.) Delays from subsequent positions must ensure all delaying units are committed to each of the series of battle positions or across the area of operation on the same phase line. Most of the delaying force is located well forward. Mission dictates the delay from one battle position or phase line to the next. Delaying unit movement is staggered so not all forces are moving at the same time.
    Watch the following video to learn more about Delays from subsequent positions.
    VIDEO - Figure 3-4. Delay from subsequent positions
    3-36. Withdrawal is a planned retrograde operation, which a force in contact disengages from an enemy force, and moves in a direction away from the enemy. Although the leader avoids withdrawing from action under enemy pressure, it is not always possible. Withdrawal is used to preserve the force or release it for a new mission.
    3-37. Withdrawals are inherently dangerous. They involve moving units to the rear and away from what is usually a stronger enemy force. The heavier the previous fighting and closer the contact with the enemy, the more difficult the withdrawal. Units usually confine rearward movement to times and conditions when the advancing enemy force cannot observe the activity or easily detect the operation. OPSEC is extremely important, especially crucial during the initial stages of a delay when most of the functional and sustainment forces displace.
    Planning a Withdrawal
    3-38. The leader plans and coordinates a withdrawal in the same manner as a delay. METT-TC applies differently because of differences between a delay and withdrawal. A withdrawal always begins under the threat of enemy interference. Because the force is most vulnerable when the enemy attacks, the leader plans for a withdrawal under pressure. The leader then develops contingencies for a withdrawal without pressure. In both cases, the leaders main considerations are to ─
    Plan a deliberate break from the enemy. Displace the main body rapidly, free of enemy interference. Safeguard withdrawal routes. Retain sufficient maneuver, functional/multi functional support and sustainment capabilities throughout the operation supporting forces in contact with the enemy. Assisted or Unassisted
    3-39. Withdrawals may be assisted or unassisted. They may or may not take place under enemy pressure. These two factors combined produce four variations. (See figure 3-5.) The figure below depicts the mission graphic for a withdrawal and withdrawal under enemy pressure. The withdrawal plan considers which variation the force currently faces.
    Figure 3-5. Types of withdrawals
    3-40. Leaders prefer to conduct a withdrawal while not under enemy pressure and without assistance. Actions by the enemy, as well as additional coordination needed because of presence of an assisting unit, complicate the operation.
    3-41. During an assisted withdrawal, the assisting force occupies positions to the rear of the withdrawing unit and prepares to accept control of the situation. Both forces closely coordinate the withdrawal. A withdrawing force can receive assistance from another force in the form of ─
    Additional security for the area through which the withdrawing force will pass. Information concerning withdrawal routes (reconnaissance and maintenance). Forces to secure choke points or key terrain along withdrawal routes. Elements to assist in movement control, such as traffic control points. Required maneuver, direct fire support and sustainment, which can involve conducting a counterattack to assist the withdrawing unit in disengaging from the enemy. 3-42. During an unassisted withdrawal, the withdrawing unit establishes routes and develops plans for the withdrawal. It establishes the security force as a rear guard while the main body withdraws. Sustainment and protection forces usually withdraw first, followed by combat forces. As the unit withdraws, the detachment left in contact (DLIC) disengages from the enemy and follows the main body to its final destination.
    3-43. In an unassisted platoon withdrawal, the platoon leader may designate one squad to execute the DLIC mission for the platoon, or constitute the DLIC using elements from the remaining rifle squads with the platoon sergeant as the DLIC leader. Figure 3-6 shows an example of an unassisted withdrawal.
    VIDEO - Figure 3-6. Platoon unassisted withdrawal
    3-44. In a withdrawal under enemy pressure, all units withdraw simultaneously when available routes allow, using delaying tactics to fight their way to the rear. When simultaneous withdrawal of all forces is not practical, the leader decides the order of withdrawal. Several factors influence this decision─
    Subsequent missions. Availability of transportation assets and routes. Disposition of friendly and enemy forces. Level and nature of enemy pressure. Degree of urgency associated with the withdrawal.  
    3-45. Retirement is a task employing to move a force not in contact to the rear. Retirement is a form of retrograde, which a force not in contact with the enemy moves away from the enemy. A retiring unit organizes for combat but does not anticipate interference by enemy ground forces. Typically, another unit’s security force covers the movement of one formation as the unit conducts a retirement. However, mobile enemy forces, unconventional forces, air strikes, air assaults, or long-range fires may attempt to interdict the retiring unit. The leader plans for enemy actions and organizes the unit to fight in self-defense. The leader usually conducts retirement to reposition his forces for future operations or to accommodate the current concept of the operation. Units conduct retirements such as tactical road marches where security and speed are the most important considerations. (Refer to chapter 5 of this publication for more information.)
  5. --Order of Events

    3-46. Usually, as part of a larger element, the Infantry platoon conducts the defense performing several integrated and overlapping activities. The following paragraphs focus on the tactical considerations and procedures involved in each activity. This discussion shows an attacking enemy that uses depth in its operations, but there will be situations where a platoon must defend against an enemy that does not have a doctrinal operational foundation. The platoon must be prepared to defend against such threats. This unconventional (insurgent or terrorist force) enemy situation requires a more flexible plan that allows for more responsive and decentralized control of combat power rather than spreading it evenly throughout the platoon’s area of operation. The platoon also may conduct ‘base-camp’ (Refer to FM 3-21.10 for more information.) or perimeter defense along with offense and patrolling against terrorist and insurgent forces. (Refer to chapter 6 of this publication for a discussion on patrol base activities.)
    3-47. As the platoon leader plans his defense, he generally follows this order of events ─
    Reconnaissance and surveillance (R&S) operations and enemy preparatory fires. Occupation and preparation. Approach of the enemy main attack. Enemy assault. Counterattack. Consolidation and reorganization. RECONNAISSANCE AND SECURITY OPERATIONS AND ENEMY PREPARATORY FIRES
    3-48. Security forces must protect friendly main battle area forces in order to allow them to prepare their defense. These security forces work in conjunction with and complement company and battalion security operations. The enemy will try to discover the defensive scheme of maneuver using reconnaissance elements and attacks by forward detachments and disruption elements. It also tries to breach the platoon’s tactical obstacles.
    Army Sgt. from Reconnaissance Platoon looks through the scope of his rifle.
    Security Force
    3-49. The security force’s goals normally include providing early warning, destroying enemy reconnaissance units, and impeding and harassing enemy assault elements. The security force continues its mission until directed to displace. The commander also may use security forces in his deception effort to give the illusion of strength in one area while establishing the main defense in another. While conducting this type of security operation, the Infantry platoon may simultaneously have to prepare battle positions, creating a challenging time-management problem for the commander and his subordinate leaders.
    3-50. During this activity, the Infantry platoon might be required to provide guides to pass the security force and might be tasked to close the passage lanes. The platoon also may play a role in shaping the battlefield. The platoon leader may position the platoon to deny likely enemy attack corridors to enhance flexibility and force enemy elements into friendly engagement area. When it is not conducting security or preparation tasks, the platoon normally occupies hide positions to avoid possible CBRN strikes or enemy artillery preparation.
    3-51. A leader's reconnaissance is critical during this time in order for the platoon to conduct occupation without hesitation and begin the priorities of work. The participants in the reconnaissance are the platoon leader, platoon sergeant, and selected squad leaders, forward observer, RTO, and a security element. The goals are, but not limited to, identification of enemy avenues of approach, engagement area, sectors of fire, the tentative obstacle plan, indirect fire plan, observation post, rally point and command post locations. Operational security is critical during the occupation to ensure the platoon avoids detection and maintains combat power for the actual defense. Soldiers, at all levels of the platoon, must thoroughly understand their duties and responsibilities related to the occupation; they must be able to execute the occupation quickly and efficiently to maximize the time available for planning and preparation of the defense.
    3-52. The platoon engages the enemy at a time and place where direct and indirect fire systems are maximized to achieve success within his designated area of operation. If available, as the enemy's assault force approaches the engagement area, the platoon may initiate CAS to weaken the enemy. Friendly forces occupy their actual defensive positions before the enemy reaches direct fire range and may shift positions in response to enemy actions or other tactical factors.
    Note. Long-range fires might be withheld in accordance with a higher commander's intent.
    3-53. During an assault, the enemy deploys to achieve mass at a designated point, normally employing assault and support forces. This may leave him vulnerable to the combined effects of indirect and direct fires and integrated obstacles. The enemy may employ additional forces to fix friendly elements and prevent their repositioning. Friendly counterattack forces might be committed against the enemy flank or rear, while other friendly forces may displace to alternate, supplementary, or subsequent positions in support of the commander's scheme of maneuver. All friendly forces should be prepared for the enemy to maximize employment of combat multipliers to create vulnerabilities. The enemy also is likely to use artillery, CAS, and CBRN weapons to set the conditions for the assault.
    3-54. The platoon engages the enemy. Squad leaders and team leaders control their Soldiers’ direct fires. Destroyed vital positions are reoccupied. Soldiers move to alternate positions if the primary positions become untenable. Casualties are evacuated. Mines, indirect fires to include mortars are fired. Javelins and other direct fire weapons target the enemy’s support positions.
    3-55. Under limited visibility, selected mortars and field artillery units initially may fire infared illumination if the enemy has not identified the defenders’ positions. Once the platoon engages the enemy from its primary positions, regular illumination is used. If the platoon has overhead cover and the enemy penetrates the tactical wire, fires may include variable timed fuzed HE.
    3-56. When required, final protective fires are initiated. Indirect fire systems to include FA and heavy mortars; join in firing their final protective fires concentrations until ordered to cease-fire or have exhausted their ammunition. Medium machine guns fire along their final protective lines (FPL). Soldiers fire to the flank to provide mutual support. Soldiers are resupplied with ammunition, and casualties evacuated.
    3-57. As the enemy's momentum slows or stops, friendly forces may conduct a counterattack. The counterattack might be for offensive purposes to seize the initiative from the enemy. In some cases, the purpose of the counterattack is mainly defensive such as reestablishing a position or restoring control of the sector. The Infantry platoon may participate in the counterattack as a base-of-fire element―providing support by fire for the counterattack force―or as the actual counterattack force.
    3-58. The platoon secures its defensive area by repositioning forces, destroying remaining enemy elements, processing EPW, and reestablishing obstacles. The platoon conducts all necessary sustainment functions as it prepares to continue the defense. Even when enemy forces are not actively engaging it, the platoon maintains awareness of the tactical situation and local security at all times. The platoon prepares itself for possible follow-on missions.
  6. --Common Offensive Control Measures

    3-59. The leader controls defensive tasks by using control measures to provide the flexibility needed to respond to changes in the situation and allow the defending leader to concentrate combat power at the decisive point. Defensive control measures within the leader’s area of operation include designating the security area, the battle handover line (BHL), the main battle area with its associated forward edge of the battle area, and echelon support area. The leader can use battle positions and additional direct fire control and fire support coordination measures in addition to those control measures to synchronize the employment of combat power. The leader designates disengagement lines to trigger the displacement of subordinate forces.
    Soldiers conducting a force protection patrol scan the terrain on a hilltop in Logar province, Afghanistan.
    3-60. The BHL is a designated phase line on the ground where responsibility transitions from the stationary force to the moving force and vice versa.
    3-61. A battle positionis a defensive location oriented on a likely enemy avenue of approach. Units as large as battalion task forces and as small as squads or sections use battle positions. They may occupy the topographical crest of a hill, a forward slope, a reverse slope, or a combination of all areas. The leader selects his positions based on terrain, enemy capabilities, and friendly capabilities. A leader can assign all or some subordinates battle positions within the area of operation. The types of battle positions are ─
    Primary. Alternate. Supplementary. Subsequent. Primary Position
    3-62. Primary positions cover the enemy’s most likely avenue of approach into the area. (See figure 3-7.)
    Alternate Position
    3-63. Alternate positions are those assigned when the primary position becomes untenable or unsuitable for carrying out the assigned task. (See figure 3-7.) These positions allow the defender to carry out his original task. The following considerations apply for an alternate battle position ─
    It covers the same avenue of approach or sector of fire as the primary battle position. It is located slightly to the front, flank, or rear of the primary battle position. It may be positioned forward of the primary battle position during limited visibility operations. It is employed to supplement or support positions with weapons of limited range, such as dismounted positions. Supplementary Position
    3-64. A supplementary position is a defensive position located within a unit's assigned area of operation providing sectors of fire and defensible terrain along an avenue of approach not the enemy’s expected avenue of attack. (See figure 3-7.) For example, an avenue of approach into a company's area of operation from one of its flanks could require the company to direct its platoons to establish supplementary positions to allow the platoons to engage enemy forces traveling along an avenue. The platoon leader formally assigns supplementary positions when the platoon must cover more than one avenue of approach.
    Subsequent Position
    3-65. Subsequent positions are those to which the unit expects to move during the course of the battle. A defending unit may have a series of subsequent positions. (See figure 3-7.) Subsequent positions also can have primary, alternate, and supplementary positions associated with them.

    VIDEO - Figure 3-7. Primary, alternate, supplementary, and subsequent battle positions
    Strong Point
    3-66. A strongpoint is a heavily fortified battle position tied to a natural or reinforcing obstacle to create an anchor for the defense or to deny the enemy decisive or key terrain. (See figure 3-8.) The mission to create and defend a strongpoint implies retention of terrain to stop or redirect enemy formations. Strongpoints require extensive time, engineer support, and Class IV resources to construct. A strongpoint also is used to─
    Canalize enemy forces. Canalize is a mission task in which the leader restricts enemy movement to a narrow zone by exploiting terrain coupled with the use of obstacles, fires, or friendly maneuver. Contain enemy forces. Contain is a mission task requiring the leader to stop, to hold, or to surround enemy forces or to cause them to center their activity on a given front and prevent them from withdrawing any part of forces for use elsewhere. Note. A minimally effective strongpoint typically requires a one-day effort from an engineer unit the same size as the unit defending the strong point. (Refer to ADRP 3-90 for more information.)
    Figure 3-8. Platoon strongpoint battle position
    3-67. The forward edge of the battle area is the foremost limits of a series of areas in which ground combat units are deployed, excluding the areas in which the covering or screening forces are operating, designated to coordinate fire support, the positioning of forces, or the maneuver of units.
    3-68. The main battle area is the area in a defense where the leader intends to deploy the bulk of the unit’s combat power and conduct decisive operations to defeat an attacking enemy. The defending leader‘s major advantage is the ability to select the ground on which the battle takes place. The defender positions subordinate forces in mutually supporting positions in-depth to absorb enemy penetrations or canalize them into prepared engagement area, defeating the enemy’s attack by concentrating the effects of overwhelming combat power. The natural defensive strength of positions determines the distribution of forces in relation to both frontage and depth. In addition, defending units typically employ field fortifications and obstacles to improve the terrain’s natural defensive strength. The main battle area also includes the area where the defending force creates an opportunity to deliver a decisive counterattack to defeat or destroy the enemy.
  7. --Sequence of the Defense

    3-69. Usually as part of a larger force, the Infantry platoon conducts the defense performing several integrated and overlapping activities.
    3-70. As in the offense, this section divides execution into five steps for discussion purposes. These steps are ─
    Gain and maintain enemy contact. Disrupt the enemy. Fix the enemy. Maneuver. Follow through/counterattack. 3-71. These steps may not occur sequentially; they may occur simultaneously. The first three steps are usually shaping operations and depending on the circumstances, either of the last two steps may be the decisive operation. (Refer to FM 3-90-1 for more information.)
    3-72. Gaining and maintaining enemy contact in the face of the enemy’s determined efforts to destroy friendly reconnaissance assets is vital to the success of the defense. As the enemy’s attack begins, the defending unit’s first concerns are to identify committed enemy units’ positions and capabilities, determine the enemy’s intent and direction of attack, and gain time to react. The platoon leader uses the information available to him, in conjunction with military judgment, to determine the point at which the enemy commits to a COA.
    3-73. Early detection of the enemy’s decisive operation provides the leader with reaction time to adjust the fixing force’s positions and shape the enemy penetration, which, in turn, provides the time necessary to commit the striking force. The striking force leader requires as close to real-time updates of enemy situation as possible to ensure the striking force engages the enemy at the right location and time.
    3-74. The leader executes shaping operations to disrupt the enemy regardless of enemy’s location within the area of operation. After making contact with the enemy, the leader seeks to disrupt the enemy’s plan, ability to control forces, and the combined arms team. Ideally, the results of leader’s shaping operations should force a disorganized enemy, whose ability to synchronize its elements has been degraded, to conduct movement to contact against prepared defenses. Once the process of disrupting the attacking enemy begins, it continues throughout the defense.
    3-75. Whenever possible the leader sequences these shaping operations, to include enemy command and control warfare, so the impact of effects coincides with the commitment of the striking force. Generating a tempo temporarily paralyzes enemy command and control, the intensity of these shaping operations may increase dramatically on the commitment of the striking force. The leader continues to conduct shaping operations once the striking force commits to prevent enemy forces from outside the operational area from interfering with executing the decisive counterattack.
    3-76. When conducting an area defense, the leader does everything possible to limit the options available to the enemy. In addition to disrupting the enemy, the leader conducts shaping operations to constrain the enemy into a specific COA, control enemy movements, or fix the enemy in a given location. These actions limit the enemy’s options. While executing these operations, the leader continues to find, and to delay or to eliminate enemy follow-on reserve forces to keep them from entering the main battle area.
    3-77. The leader has several options to help fix an attacking enemy force. The leader can design shaping operations, such as securing the flanks and point of a penetration, to fix the enemy and to allow friendly forces to execute decisive maneuver elsewhere.
    3-78. The leader uses obstacles covered by fire to fix, to turn, to block, or to disrupt to limit the enemy’s available options. Properly executed obstacles are a result of synthesis of top-down and bottom-up obstacle planning and emplacement. Blocking forces also can affect enemy movement. A blocking force may achieve its mission from a variety of positions depending on METT-TC.
    3-79. During the defense, the decisive operation occurs in the main battle area. This is where the effects of shaping operations, coupled with sustaining operations, combine with the decisive operations of the main battle area force to defeat the enemy. The leader’s goal is to prevent the enemy’s increased advance through a combination of fires from prepared positions, obstacles, and possible counterattack.
    3-80. Situational understanding is critical in establishing the conditions initiating the striking force’s movement and in determining the general area serving as a focus for counterattacking. It includes identifying those points in time and space where the counterattack proves decisive. A force-oriented objective or an engagement area usually indicates the decisive point.
    3-81. The purpose of the defense is to retain terrain and create conditions for a counteroffensive regaining the initiative. The area defense does this by causing the enemy to sustain unacceptable losses short of all decisive objectives. An area defense allows the leader transition to an attack. An area defense also could result in a stalemate with both forces left in contact with each other. Finally, it could result in the defender being overcome by the enemy attack and needing to transition to a retrograde. All decisions to withdraw must take into account the current situation in adjacent defensive areas. Only the leader who ordered the defense can designate a new forward edge battle area or authorize a retrograde.
    3-82. The intent of the defense is creating the opportunity to transition to the offense. In a mobile defense, a transitional opportunity generally results from the success of the striking force’s attack. The leader exploits success and attempts to establish conditions for a pursuit if the result of the leader’s assessment of the striking force’s attack shows there are opportunities for future offensive missions. If the conduct of the mobile defense is unsuccessful and enemy retains the initiative, the leader must either reestablish a viable defense or conduct a retrograde.
  8. --Priority of Work

    3-83. Priority of work is a set method of controlling the preparation and conduct of a defense. Tactical SOPs should describe priority of work including individual duties. The platoon leader changes priorities based on the situation. All leaders in the platoon should have a specific priority of work for their duty position. Although listed in sequence, several tasks are performed at the same time. An example priority of work sequence is as follows ─
    Post local security. Position and assign sectors of fire for each BFV or ICV. Establish the platoons reconnaissance and surveillance. Position Javelins, machine guns, and Soldiers; assign sectors of fire. Position other assets (platoon command post). Designate final protective lines and final protective fires. Clear fields of fire and prepare range cards and area of operations sketches. Adjust indirect fire final protective fires. The firing unit fire direction center should provide a safety box clearing of all friendly units before firing adjusting rounds. Prepare fighting positions. Install wire communications, if applicable. Emplace obstacles and mines. Mark (or improve marking for) target reference points and direct fire-control measures. Improve primary fighting positions such as overhead cover. Prepare alternate and supplementary positions. Establish sleep and rest plan. Reconnoiter movements. Rehearse engagements and disengagements or displacements. Adjust positions and control measures as required. Stockpile ammunition, food, and water. Dig trenches between positions. Reconnoiter routes. Continue to improve positions. PLATOON LEADER
    3-84. Many duties can be delegated to subordinates, but the platoon leader ensures they are done. This includes -
    Ensuring local security and assigning observation post responsibility. Conducting a leader's reconnaissance with the platoon sergeant and selected personnel. Confirming or denying significant deductions or assumptions from the mission analysis. Confirming the direct fire plan, to include engagement area, sectors of fire, position essential weapons, and fire control measures. Designating primary, alternate, supplementary, and subsequent positions supporting the direct fire plan, for platoons, sections, and supporting elements. Requiring squads to conduct coordination. Integrating indirect fire plan and obstacles to support the direct fire plan. Designating the general platoon command post location, and positioning essential weapons. Checking the platoon command post and briefing the platoon sergeant on the situation and logistics requirements. Upon receipt of the squads’ area of operations sketches, makes two copies of the platoon defensive area of operations sketch and fire plan, retaining one copy and forwarding the other copy to the company. (See figure 3-9.) Confirming the direct fire plan and squad positions before digging starts. Coordinating with the left and right units. Checking with the company commander for all changes or updates in the orders. Finishing the security, deception, counterattack, and obstacle plans. Walking the platoon positions after they are dug. Confirming clear fields of fire and complete coverage of the platoon’s entire area of operations by all essential weapons. Looking at the defensive plan from an enemy point of view, conceptually and physically. Checking dissemination of information, interlocking fires, and dead space. Ensuring immediate correction of deficiencies. Ensuring rehearsals are conducted and obstacle locations reported. Figure 3-9. Platoon defensive area of operation sketch
    3-85. Duties and responsibilities include —
    Establishing the platoon command post and ensures wire communications link the platoon, squads, and attached elements, if applicable. Establishing casualty collection points, platoon logistics release points, and detainee collection points, and locating company level points. Briefing squad leaders on the platoon command post location, logistics plan, and routes between positions. Assisting the platoon leader with the sector of fire and area of operations sketch. Requesting and allocating pioneer tools, barrier materiel, rations, water, and ammunition. Walking the positions with the platoon leader. Supervising emplacement of squads, essential weapons, check range cards, and area of operations sketches. Establishing routine security or alert plans, radio watch, and rest plans and briefing the platoon leader. Supervising continuously and assisting the platoon leader with other duties as assigned. Selecting slit trench location and ensuring it is properly marked. SQUAD LEADERS
    3-86. The squad leader —
    Emplaces local security. Confirms positioning and assigned sectors of fire for his squad. Confirms positioning and assigned sectors of fire for the CCMS and medium machine gun teams. Positions and assigns sectors of fire for automatic rifleman, grenadiers, and riflemen. Establishes command post and wire communications. Confirms designate FPL and final protective fires. Clears fields of fire and prepares range cards. Prepares squad range card and area of operations sketches. Digs fighting positions. Establishes communication and coordination within the platoon, and adjacent units. Coordinates with adjacent units. Reviews sector of fire and area of operations sketches. Emplaces antitank and Claymores, then wire and other obstacles. Marks or improves marking for target reference points and other fire control measures. Improves primary fighting positions and adds overhead cover (stage 2). Prepares supplementary and alternate positions (same procedure as the primary position). Establishes sleep and rest plans. Distributes and stockpiles ammunition, food, and water. Digs trenches to connect positions. Continues to improve positions, construct revetments, replace camouflage, and add to overhead cover. FORWARD OBSERVER
    3-87. The FO —
    Assists the platoon leader in planning the indirect fires to support defensive missions. Advises the platoon leader on the status of all firing units, and on the use of obscurants or illumination. Coordinates with the Infantry company fire support officer, firing units, and squad leaders to ensure the fire plan is synchronized and fully understood. Ensures the indirect fire plan is rehearsed and understood by all. Ensures all final protective fires are adjusted as soon as possible. Develops an observation plan. Coordinates and rehearses all repositioning of observers within the platoon area of operations to ensure they can observe targets or areas of responsibility. Develops triggers. Reports information collection activities. Ensures redundancy in communications. ADJACENT UNIT COORDINATION
    3-88. The ultimate goal of adjacent unit coordination is to ensure unity of effort in accomplishment of the Infantry mission. Items adjacent units coordinate include —
    Unit positions, including locations of vital leaders’ call signs and frequencies. Locations of observation posts and patrols. Overlapping fires (to ensure direct fire responsibility is clearly defined). Target reference points). Alternate, supplementary, and subsequent battle positions. Indirect fire information. Obstacles (location and type). Air defense considerations, if applicable. Routes to be used during occupation and repositioning. Sustainment considerations.
  9. --Coordination

    3-89. In the defense, coordination ensures that units provide mutual support and interlocking fires. In most circumstances, the platoon leader conducts face-to-face coordination to facilitate understanding and to resolve issues effectively. However, when time is extremely limited, digital coordination may be the only means of sending and receiving this information. The platoon leader should send and receive the following information using his radio or mission command system before conducting face-to-face coordination:
    Location of leaders. Location of fighting positions. Location of observation points and withdrawal routes. Location and types of obstacles. Location, activities, and passage plan for scouts and other units forward of the platoon’s position. Platoon’s digital sector sketch. Location of all Soldiers and units operating in and around the platoon’s area of operation.  
      3-90. Current techniques for coordination hold true for units that are digitally equipped. If a digitized and a non digitized unit are conducting adjacent unit coordination, face-to-face is the preferred method. The leader of the digitized unit has the option to enter pertinent information about the non digitized unit into mission command systems for later reference. The digitally equipped platoon leader should show the adjacent unit leader his digital sector sketch. If face-to-face coordination is not possible, leaders share pertinent information by radio.
  10. --Security

    3-91. Security in the defense includes all active and passive measures taken to avoid detection by the enemy, deceive the enemy, and deny enemy reconnaissance elements accurate information on friendly positions. The two primary tools available to the platoon leader are observation posts and patrols. In planning for the security in the defense, the platoon leader considers the military aspects of terrain: observation and fields of fire, avenues of approach, key terrain, obstacles and cover, and concealment. He uses his map to identify terrain that will protect the platoon from enemy observation and fires, while providing observation and fires into the engagement area. He uses intelligence updates to increase his situational understanding, reducing the possibility of the enemy striking at a time or in a place for which the platoon is unprepared.
    3-92. Current mission commands systems allow mechanized squads to digitally transmit enemy situation and observation reports. This simplifies the reporting process without compromising security. Dismounted observation posts still render reports by frequency modulation radio transmission.
    3-93. An observation post provides the primary security in the defense. Observation posts provide early warning of impending enemy contact by reporting direction, distance, and size. It detects the enemy early and sends accurate reports to the platoon. The platoon leader establishes observation posts along the most likely enemy avenues of approach into the position or into the area of operation. Leaders ensure that observation posts (mounted or dismounted) have communication with the platoon.
    3-94. Early detection reduces the risk of the enemy overrunning the observation post. Observation post may be equipped with a Javelin command launch unit; class 1 unmanned aircraft system; seismic, acoustic, or frequency detecting sensors to increase its ability to detect the enemy. They may receive infrared trip flares, infrared parachute flares, infrared M203 or M320 rounds, and even infrared mortar round support to illuminate the enemy. The platoon leader weighs the advantages and disadvantages of using infrared illumination when the enemy is known to have night vision devices that detect infrared light. Although infrared and thermal equipment within the platoon enables the platoon to see the observation post at a greater distance, the observation post should not be positioned outside the range of the platoon’s small-arms weapons.
    3-95. To further reduce the risk of fratricide, observation posts use GPS to navigate to the exit and entry point in the platoon’s position. The platoon leader ensures he submits an observation post location to the company team commander to ensure a no fire area is established around each observation post position.
    3-96. Platoons actively patrol in the defense. Patrols enhance the platoon’s ability to fill gaps in security between observation posts. The platoon leader forwards his tentative patrol route to the commander to ensure they do not conflict with other elements within the company team. The commander forwards the entire company team’s patrol routes to the task force. This allows the operations and intelligence staff officers to ensure all routes are coordinated for fratricide prevention and no gaps are present. The patrol leader may use a GPS to enhance his basic land navigational skills as he tracks his patrol’s location on a map, compass, and pace count or odometer reading.
    3-97. After a range card is completed, the position should be marked with ground stakes. This enables the vehicle or a replacement vehicle to reoccupy the position and to use the range card data. The steps in marking a vehicle position are staking the position and moving into position. Each are described below.
    Stake the Position
    3-98. Before the vehicle is moved, the position should be staked. Three stakes must effectively mark the position as shown in figure 3-10.
    Figure 3-10. Stake the position
    3-99. One stake is placed in front of the vehicle, centered on the driver’s station and just touching the hull. The stake should be long enough for the driver to see it when in position. The other two stakes are placed parallel to the left track and lined up with the hub on the front and rear wheels. The stakes should be placed close to the vehicle with only enough clearance to move the vehicle into position.
    3-100. The stakes should be driven firmly into the ground. Engineer tape or luminous tape can be placed on the friendly side of the stakes so that the driver can see them. A rock is placed at each of the front two corners of the vehicle to assist in reoccupation if the stakes are lost.
    Move into Position
    3-101. If the situation permits, a ground guide can be used to assist the driver. If a ground guide cannot be used, the driver moves the vehicle in, parallel to the side stakes, with the front stake centered on the driver’s station. Once the vehicle is in position, the gunner should index the range and azimuth for one of the TRPs on the range card. If the sight is aligned on the TRP, the vehicle is correctly positioned. If the sight is not aligned on the TRP, the gunner should tell the driver which way to move the vehicle to align the sight on the target. Only minor adjustments should be necessary. If the stakes are lost and the position is not otherwise marked, the vehicle is moved to the approximate location. The vehicle commander or gunner can use a compass to find the left and right limits. The vehicle should be moved if time allows until it is within 6 to 8 inches of exact position.
  11. --Remount Point

    3-102. The platoon leader selects a remount point that permits the rapid loading of the dismounted element into vehicles, while minimizing both the dismounted Soldier’s and vehicles exposure to enemy fire. He tries to locate the remount point as close as possible to his dismounted element. Squad leaders ensure that their Soldiers know the remount point location. When moving to the vehicles, the dismounted element ensures that they do not mask the BFV or ICV fields of fire.
    3-103. Three remount point locations exist: near the dismounted element, near the mounted element, or between the two. Positioning the remount point near the dismounted element is preferred if it does not unnecessarily expose the vehicles to enemy fire. Based on the situation however, the platoon leader may have to accept risk and expose his BFVs or ICVs to remount his platoon. Locating the remount point near the vehicle is preferred if the area around or the mounted route to the dismounted element is exposed to enemy fire, and include a covered dismounted route back to the vehicles. The platoon leader selects a remount point between the two elements when both can reach it without unnecessarily exposing themselves to enemy fire.
  12. *****Common Defensive Planning Considerations*****

    3-104. Planning a defensive task is a complex effort requiring detailed planning and extensive coordination. In the defense, synchronizing the effects of the Infantry platoons and squads combat and supporting systems enables the platoon leader to apply overwhelming combat power against selected advancing enemy forces. This unhinges the enemy commander’s plan and destroys his combined arms team. As an operation evolves, the Infantry leader knows a shift to decisive and shaping operations is a probability to press the fight and keep the enemy off balance. Warfighting functions provide the Infantry leader a means and structure for planning, preparing, and executing the defense. The following paragraphs discuss the synchronization and coordination of activities within each warfighting function critical to the success of the Infantry platoon and squad. This section also discusses urban and mountainous defensive planning considerations.
    Note. To avoid redundancy, the six warfighting functions for the offense are similar to the six-warfighting functions for the defense. Commander’s intent and METT-TC determines how they are applied.
  13. --Mission Command

    3-105. The first step is the expression of the leader’s vision of anticipated enemy actions integrated with the Infantry companies IPB. The Infantry battalion and company IPB should not differ significantly, giving the Infantry platoon and squad a clear understanding of how the Infantry battalion and company commanders envision the enemy fight and plan for the operation. The Infantry company commander and CoIST  refine the IPB to focus on the details of the operation in the company area of operation . The platoon leader refines his IPB to focus on the details of the mission in the Infantry platoon and squad area of operation. The Infantry battalion commander usually defines where and how the Infantry battalion will defeat or destroy the enemy. The Infantry company commander and platoon leader then defines how they envision how their units will execute their portion of the battalion fight.
    A platoon leader gives a short briefing to his platoon.
  14. --Movement and Maneuver

    3-106. Maneuver considerations employ direct fire weapons on the battlefield. In the defense, weapons positioning is critical to the Infantry platoon's and squad’s success. Weapons positioning enables the platoon to mass fires at critical points on the battlefield and shift fires as necessary. The platoon leader exploits the strengths of his weapons systems while minimizing the platoon's exposure to enemy observation and fires.
    3-107. If the platoon or squad are designated in a reserve role positioning the reserve in a location where it can react to several contingency plans is vital to success. The platoon leader considers terrain, traffic of roads, potential engagement area, probable points of enemy penetrations, and commitment time. The Infantry battalion commander can have a single reserve under battalion control, or, if the terrain dictates, the Infantry company can designate its own reserves. The reserve should be positioned in a covered and concealed position. Information concerning the reserve may be considered EEFI and protected from enemy reconnaissance. The commander might choose to position his reserve forward initially to deceive the enemy, or to move the reserve occasionally to prevent it from being targeted by enemy indirect fires.
    3-108. Dispersing positions laterally and in-depth helps to protect the force from enemy observation and fires. The positions are established in depth, allowing sufficient maneuver space within each position to establish in depth placement of weapons systems, and Infantry elements. Engagement areas are established to provide for the massing of fires at critical points on the battlefield. Sectors of fire are established to distribute and shift fires throughout the extent of the engagement area. Once the direct fire plan is determined, fighting positions are constructed in a manner to support the fire plan.
    3-109. Flank positions enable a defending force to fire on an attacking force moving parallel to the defender's forces. A flank position provides the defender with a larger and more vulnerable target while leaving the attacker unsure of the defense location. Major considerations for employment of a flank position are the defender's ability to secure the flank and his ability to achieve surprise by remaining undetected. Fire control and fratricide avoidance measures are critical considerations in the employment of flank positions. (See appendix B of this publication for more information.)
    3-110. Disengagement and displacement allow the platoon to retain its flexibility and tactical agility in the defense. The ultimate goals of disengagement and displacement are to enable the platoon to avoid being fixed or decisively engaged by the enemy. The overarching factor in a displacement is to maintain a mobility advantage over the enemy. The platoon leader must consider several important factors in displacement planning. These factors include, among others —
    The enemy situation, for example, an enemy attack with one company-size enemy unit might prevent the platoon from disengaging. Disengagement criteria. Availability of direct fire suppression that can support disengagement by suppressing or disrupting the enemy. Availability of cover and concealment, indirect fires, and obscurants to assist disengagement. Obstacle integration, including situational obstacles. Positioning of forces on terrain that provides an advantage to the disengaging elements such as reverse slopes or natural obstacles. Identification of displacement routes and times when disengagement or displacement will take place. Routes and times are rehearsed. The size of the friendly force that must be available to engage the enemy in support of the displacing unit. 3-111. While disengagement and displacement are valuable tactical tools, they can be extremely difficult to execute in the face of a rapidly moving enemy force. In fact, displacement in contact poses such great problems that the platoon leader thoroughly plans for it and rehearses displacement before conducting the defense. He then carefully evaluates the situation when displacement in contact becomes necessary to ensure it is feasible and does not result in unacceptable personnel or equipment losses.
    3-112. Disengagement criteria dictate to subordinate elements the circumstances, in which they will displace to alternate, supplementary, or subsequent positions. The criteria are tied to an enemy action, such as an enemy unit advancing past a certain phase line. They also are linked to the friendly situation. For example, the criteria might depend on whether artillery or an overwatch element can engage the enemy. Unique disengagement criteria are developed during the planning process for each specific situation.
    3-113. The attacking enemy force must not be allowed to bring direct and indirect fires to bear on a disengaging friendly force. Direct fires from the base-of-fire element, employed to suppress or disrupt the enemy, are the most effective way to facilitate disengagement. The platoon may receive base of direct fire support from another element in the company, but in most cases, the platoon establishes its own base-of-fire element. Having an internal base of fire requires the platoon leader to sequence the displacement of his forces.
    3-114. The platoon and subordinate squads use covered and concealed routes when moving to alternate, supplementary, or subsequent positions. Regardless of the degree of protection the route itself affords, the platoon and squads try to rehearse the movement prior to contact. Rehearsals increase the speed at which they can conduct the move and provide an added measure of security. The platoon leader makes a concerted effort to allocate available time to rehearse movement in limited visibility and degraded conditions.
    Infantry Soldier practices camouflage, cover and concealment.
    3-115. Artillery or mortar fires assist the platoon during disengagement. Suppressive fires slow the enemy and cause him to seek cover. Smoke obscures the enemy's vision, slows his progress, or screens the defender's movement out of the battle position or along his displacement route.
    3-116. Obstacles are integrated with direct and indirect fires. By slowing and disrupting enemy movement, obstacles provide the defender with the time necessary for displacement and allow friendly forces to employ direct and indirect fires against the enemy. The Modular Pack Mine System (MOPMS) also can be employed in support of the disengagement, to either block a key displacement route once the displacing unit has passed through it or close a lane through a tactical obstacle. The location of obstacles in support of disengagement depends on METT-TC. Ideally, an obstacle should be positioned far enough away from the defender that enemy elements could be engaged on the far side of the obstacle while keeping the defender out of range of the enemy's massed direct fires.
    3-117. Mobility operations in the defense ensure the ability to reposition forces, delay, and counterattack. Initially during defensive preparations, mobility operations focus on the ability to resupply, reposition, and conduct rearward and forward passage of forces, materiel, and equipment. Once defensive preparations are complete, the focus normally shifts to supporting the platoon reserve, local counterattacks, and the higher headquarters counterattack or reserve. Priorities set by the company may specify routes for improvement in support of such missions. Normally, most engineer assets go to survivability and countermobility. At a set time or trigger, engineers disengage from obstacle and survivability position construction and start preparing for focused mobility missions. The platoon leader analyzes the scheme of maneuver, obstacle plan, and terrain to determine mobility requirements. Critical considerations may include —
    Lanes and gaps in the obstacle plan. Lane closure plan and subunit responsibility. Route reconnaissance, improvement, and maintenance. COUNTERMOBILITY
    3-118. To succeed in the defense, the platoon leader integrates individual obstacles into direct and indirect fire plans, considering the intent for each obstacle group. (Refer to ATTP 3-90.4 for more information on countermobility in the defense.) Obstacles are normally constructed by engineers with help from the platoon. In the defense, the platoon or squad uses obstacles to:
    Slow the enemy’s advance to give the platoon or squad more time to mass fires on him. Protect defending units. Canalize the enemy into places where he can easily be engaged. Separate the enemy’s tanks from his infantry. Strengthen areas that are lightly defended.  
    3-119. Obstacle intent includes the target and desired effect (clear task and purpose) and the relative location of the obstacle group. The purpose influences many aspects of the operation, from selecting and designing obstacle sites to conducting the defense. Normally, the company commander designates the purpose of an obstacle group. When employing obstacles, the leader considers the following principles:
    Support the tactical plan. Obstacles supplement combat power, decrease the mobility of the enemy, and provide security for the platoon. While considering enemy avenues of approach, he also considers his own movement requirements, such as routes for resupply, withdrawal, counterattacks, patrols, and observation posts. Tie in. He ties in his reinforcing obstacles with existing obstacles. He must also tie in the obstacle plan with his plans for fires. Covered by observation and fire. He ensures that all obstacles are covered by observation and fire. This reduces the enemy’s ability to remove or breach the obstacles and increases the possibilities of placing fire on the enemy when he encounters the obstacle. Constructed in depth. He emplaces obstacles so that each new obstacle encountered by the enemy attrites the enemy force and causes a desired and controlled reaction. Proper use of obstacles in depth wears the enemy down and significantly increases the overall effect. Employed for surprise. An obvious pattern of obstacles would divulge locations of units and weapons. Friendly forces must avoid readily discernable, repetitive patterns.  
    Tactical Obstacles
    3-120. The company commander assigns obstacle groups, and tells the platoon leaders and engineers what he wants to do to the enemy, and then he resources the groups accordingly. Obstacle intent includes these elements ─
    The target, which is the enemy force that the commander wants to affect with fires and tactical obstacles. The commander identifies the target's size, type, echelon, avenues of approach, or any combination of these. The obstacle effect describes how the commander wants to attack enemy maneuver with obstacles and fires. Tactical obstacles block, turn, fix, or disrupt. Obstacle effect integrates the obstacles with direct and indirect fires. The relative location is where the commander wants the obstacle effect to occur against the targeted enemy force. The commander initiates the obstacle integration process after identifying where on the terrain the obstacle will most decisively affect the enemy. For example, the company commander might say, "Deny the enemy access to our flank by turning the northern, mechanized Infantry battalion into our EA. Allow companies B and C to mass their fires to destroy the enemy." Scatterable minefield systems and submunitions are the main means of constructing tactical obstacles. These systems, with their self- and command-destruct capabilities, are flexible, and they aid in rapid transitions between offensive and defensive tasks. They do this better than other constructed obstacles. The force constructs conventional minefields and obstacles only for a deliberate, long-term defense. In those cases, the company and platoons usually are augmented with assets from a divisional engineer battalion. Table 3-2 shows the symbols for each obstacle effect, and it describes the purpose and characteristics of each. Table 3-2. Obstacle effects
    Protective Obstacles
    3-121. Infantry platoons plan and construct their own protective obstacles. For best effect, protective obstacles are tied into existing or tactical reinforcing obstacles. The platoon can use mines and wire, or it might receive additional materiel from company, Class IV or V supply point. The platoon also might conduct any other required coordination, such as needed in a relief in place, to recover or destroy the obstacle ─
    In planning protective obstacles, the platoon leader evaluates the potential threat to the platoon’s position. Then, employs the best system for that threat. Protective obstacles usually are located beyond hand grenade distance (40 to 100 meters) from the Soldier's fighting position, and may extend out 300 to 500 meters to tie into tactical obstacles and existing restricted terrain. As with tactical obstacles, the platoon leader should plan protective obstacles in-depth and try to maximize the range of his weapons. When planning protective obstacles, the platoon leader considers preparation time, the burden on the logistical system, the Soldiers' loads, and the risk of loss of surprise.  
    3-122. The three types of wire obstacles (see figure 3-11) are protective, tactical, and supplementary ─
    Protective wire can be a complex obstacle providing all-around protection of a platoon perimeter. It also might be a simple wire obstacle on the likely dismounted avenue of approach into a squad ambush position. Command-detonated M18 Claymores can be integrated into the protective wire or used separately. Tactical wire is positioned to increase the effectiveness of the platoon's fires. Usually, it is positioned along the friendly side of the medium machine gun FPL. Tactical minefields also may be integrated into these wire obstacles or used separately. Supplementary wire obstacles can break up the line of tactical wire. This helps prevent the enemy from locating friendly weapons (particularly the medium machine guns) by following the tactical wire. Figure 3-11. Protective wire obstacles
    Obstacle Lanes
    3-123. The platoon might be responsible for actions related to lanes through obstacles. These duties can include marking lanes in an obstacle, reporting locations of the start and ends of each lane, operating contact points, providing guides for elements passing through the obstacle, and closing the lane.
    Situational Obstacle
    3-124. A situational obstacle is planned and possibly prepared before a mission, but it executes only if specific criteria are met. It gives the platoon leader the flexibility to emplace tactical obstacles based on battlefield development ─
    The platoon leader anticipates situations that require maneuver and fire plan modifications to defeat the threat, and considers the use of situational obstacles to support these modifications. By their very nature, situational obstacles must be quickly installable, but still achieve the desired effect. Therefore, scatterable mines (SCATMINEs) such as MOPMS, Hornets, and Volcanoes are the most common versions used at the platoon level. However, situational obstacles can consist of any type of individual obstacle. The platoon leader considers where he can employ situational obstacles. He ensures the combination of fires and obstacles are enough to achieve the obstacle effect. The platoon leader identifies execution triggers; situational obstacles are triggered based on friendly actions, enemy actions, or a combination of both. Finally, the platoon leader withholds execution of a situational obstacle until the obstacle effect is required. Once committed, those assets are no longer available to support any other mission. The platoon leader also considers that SCATMINEs have a self-destruct time. Emplacing an obstacle too soon can cause the mines to self-destruct before the enemy arrives.
  15. --Intelligence

    3-125. The Infantry platoon leader never has all the information needed about the enemy. Therefore, the platoon leader obtains or develops the best possible IPB (intelligence preparation of the battlefield) products, conducts continuous reconnaissance, and integrates new and updated intelligence throughout the operation. He may need to request information through the CoIST (Company intelligences support team) from the battalion staff to answer platoon information requirements. (Refer to FM 3-21.10 for more information.)
    3-126. As with all tactical planning, IPB is a critical part of defensive planning. It helps the platoon leader define where to concentrate combat power, where to accept risk, and where to plan potential decisive operations. To aid in the development of a flexible defensive plan, the IPB must present all feasible enemy courses of action. The essential areas of focus are ─
    Analyze terrain and weather. Determine enemy force size and likely courses of action with associated decision points. Determine enemy vulnerabilities and high value targets. Impact of civilian population on the defense. 3-127. The platoon leader, in coordination with the CoIST, base determinations of how and where to defeat the enemy on potential future enemy locations, the terrain, and forces available. The Infantry company may define a defeat mechanism including the use of single or multiple counterattacks to achieve success. The platoon leader analyzes the platoon’s role in the Infantry company fight and determines how to achieve success.
    Watch the following video about the job of a Military Intelligence Officer.
  16. --Fires

    3-128. For indirect fire plan to be effective in the defense, the Infantry platoon plans and executes fires in a manner, which achieves the intended task and purpose of each target. Indirect fires serve a variety of purposes in the defense, including the following ─
    Slow and disrupt enemy movement. Prevent the enemy from executing breaching operations. Destroy or delay enemy forces at obstacles using massed fires or precision munitions. Disrupt enemy support by fire elements. Defeat attacks along avenues of approach with the use of final protective fires. Disrupt the enemy to enable friendly elements to disengage or conduct counterattacks. Obscure enemy observation or screen friendly movement during disengagement and counterattacks. Provide obscurants screens to separate enemy echelons or to silhouette enemy formations to facilitate direct fire engagement. Provide illumination as necessary. Execute suppression of enemy air defense missions to support aviation operations. Infantrymen fire a 120mm mortar during a night-fire exercise.
    3-129. In developing the fire plan, the platoon leader evaluates the indirect fire systems available to provide support. Considerations when developing the plan include tactical capabilities, weapons ranges, and available munitions. These factors help the platoon leader and forward observer determine the best method for achieving the task and purpose for each target in the fire plan. The Infantry company fire support personnel contribute significantly to the platoon fight. Positioning is critical. The platoon leader, in coordination with the company fire support officer, selects positions providing his forward observer with unobstructed observation of the area of operation, ensuring survivability.
  17. --Sustainment

    3-130. In addition to the sustainment functions required for all missions, the platoon leader’s planning process includes pre-positioning of ammunition caches, identifying the positioning of company trains, and Class IV and V supply points and mine dumps.
    3-131. The platoon leader’s mission analysis may reveal the platoon's ammunition requirements during an upcoming mission exceed its basic load. This requires the platoon to coordinate with the company to preposition ammunition caches. The platoon usually positions ammunition caches at alternate or subsequent positions. The platoon also may dig in these caches and guard them to prevent their capture or destruction by the enemy.
    3-132. The Infantry company trains usually operate 500 to 1000 meters or one terrain feature to the rear of the company to provide immediate recovery and medical support. The company trains conduct evacuation (of those wounded in action -  WIA), weapons, and equipment) and resupply as required. The company trains are located in covered and concealed positions close enough to the company to provide responsive support, but out of enemy direct fire. The company first sergeant or executive officer positions the trains and supervises sustainment operations with the platoon. It is the Infantry company commander’s responsibility to ensure all subordinate units know the locations of battalion combat and field trains as well as the company(Casualty Collection Point - CCP  or Battalion Aid Station - BAS) and medical and casualty evacuation procedures. The platoon leader’s analysis determines the measures for every mission.
  18. --Protection

    3-133. Air and missile defense support to the platoon may be limited. Units should expect to use their organic weapons systems for self-defense against enemy air threats. Plan for Chemical, Biological, Radioloical and Nuclear - CBRN reconnaissance at likely locations for enemy employment of CBRN agents and hazards. Use obscurants to support disengagement or movement of forces. Assign sectors of fire to prevent fratricide and friendly fire.
    3-134. Survivability construction includes fighting positions, protective positions, and hardening. These are prepared to protect vehicles, personnel and weapons systems. Positions can be constructed and reinforced with overhead cover to increase the survivability of dismounts and crew-served weapons against shrapnel from airbursts. Vehicle fighting positions can be constructed with both hull and turret-defilade observation positions. In addition, the Infantry platoon and squad may use digging assets for ammunition caches at alternate, supplementary, or subsequent positions. All leaders must understand survivability plans and priorities. Typically, at platoon level the engineer platoon leader creates a leader’s card, which enables the platoon leader to track the survivability effort. One person in the platoon, usually the platoon sergeant is designated to enforce the plan and priorities, and ensure the completion status is reported accurately, tracked, and disseminated down to subordinate squads and attachments.
    Linear enhanced survivability position.
  19. --Additional Planning Considerations

    3-135. Additional defensive planning considerations for missions in urban and mountainous environments  include urban terrain, subterranean threats, mountainous terrain and tunnel and cave complexes. Each of these are described below.
    3-136. Infantry forces defend urban areas to defeat an attack, gain time, economize forces, protect infrastructure, protect a populace, and shape conditions for offensive or stability urban operations. Usually two or more purposes apply to urban defense tasks in urban terrain. Defensive urban operations provide leaders opportunities to turn the environment’s characteristics to the advantage of Army forces. Urban areas are ideal for the defense and enhance the combat power of defending units.
    3-137. In a built-up area, the defender takes advantage of inherent cover and concealment afforded by urban terrain. Restrictions to the attacker's ability to maneuver and observe are taken into consideration. By using the terrain and fighting from well-prepared and mutually supporting positions, a defending force can delay, block, fix, turn, disrupt, or destroy a much larger attacking force. The defense of a built-up area is organized around key terrain features, buildings, and areas that preserves the integrity of the defense and provide the defender ease of movement. The defender organizes and plans defensive missions by considering OAKOC, fire hazards, and communications restrictions. (Refer to ATTP 3-06.11 for more information.)
    Watch the following video to learn more about additional planning considerations.
    3-138. The enemy will likely use tunnels and may have the advantage of marked routes and detailed reconnaissance. Because he is able to select ambush positions and withdrawal routes, the defender typically has the element of surprise. A defended position in an underground facility can be very effective in countering enemy subterranean operations. The best underground defensive positions are well protected and canalize the enemy into a killing zone to inflict maximum casualties.
    3-139. When moving through tunnels, take great care to avoid booby traps. These are normally deployed near junctions and are often operated by tripwires. Standing water in tunnels provides excellent camouflage for antipersonnel mines and booby traps scattered on likely routes. With the battle above continuing, flooding and cave-ins are highly possible due to the likelihood of artillery barrages and the use of demolitions. Thus, identifying escape routes is essential.
    3-140. Chemical defense is a constant concern for Soldiers conducting subterranean operations. In tunnels, Soldiers may encounter chemical warfare agents as well as industrial chemicals in dense concentrations. A chemical agent alarm system, carried by the point man, provides instantaneous warning of the presence of chemical warfare agents. M8 and M9 detection papers also test for the presence of chemical agents. (Refer to ATTP 3-06.11 for more information.
    3-141. Defensive tasks in mountainous areas are conducted to resist, defeat, or destroy an enemy attack to support subsequent offensive tasks. Infantry leaders use the defense to withstand an enemy attack while preparing to seize the initiative and develop conditions favorable for transitioning to the offense. During the defense, friendly forces withstand enemy attacks and hold the enemy while preparing to seize the initiative and transition to an attack or to conduct stability tasks. A thorough understanding of the commander's intent is especially critical in the defense, which demands precise integration of all combat power.
    3-142. Forces operating in mountainous terrain often possess weapons and equipment more advanced in technology than the enemy does. Knowing this, enemy offensive tactics commonly involve short violent engagements followed by a hasty withdrawal through preplanned routes. They often strike quickly and fight only as long as the advantage of initial surprise is in their favor. Attacks may include direct fires, indirect fires, or IEDs and may be against stationary or moving forces. (Refer to ATTP 3-21.50 for more information.)
    3-143. Tunnel and complexes may be interconnected with other tunnels and caves, concealed by trapdoors or blocked dirt passages that are up to three or four feet thick. Secret passages are usually known only to selected personnel and are used mainly in emergencies. Tunnels and caves may be interconnected by much longer passages through which relatively large bodies of men may be transferred from one area to another. The connectivity of these systems often allows the enemy to move unnoticed from one area to another, eluding friendly forces.
    3-144. Characteristic of a typical tunnel or cave complex is normally superb camouflage, conceal entrances, exits and camouflage bunkers. Within the tunnel and cave complex itself, side tunnels may be concealed, trapdoors are often hidden and dead-end tunnels or caves are used to confuse the attackers. Airshafts are usually spaced at intervals throughout a tunnel or cave system. In many instances, the first indication of a tunnel or cave complex comes from direct fire received from a concealed bunker. Spoils from the tunnel or cave system may be distributed over a wide area, giving clues to its existence. (Refer to ATTP 3-21.50 for more information).
  20. *****Forms of the Defense*****

    3-145. The Infantry platoon usually defends using one of three forms of defense: defense of a linear obstacle, perimeter defense, and reverse slope. The platoon also can defend using a combination of these forms. (Refer to FM 3-90-1 for more information.)
  21. --Defense of a Linear Obstacle

    3-146. A platoon leader may conduct either an area or mobile defense along or behind a linear obstacle. The Infantry leader normally prefers an area defense because it accepts less risk by not allowing the enemy to cross the obstacle. Linear obstacles such as mountain ranges or river lines generally favor a forward defense. It is extremely difficult to deploy in strength along the entire length of a linear obstacle. The defending leader must conduct economy of force measures in some areas.
    3-147. Within an area defense, the leader’s use of a defense in-depth accepts the possibility the enemy may force a crossing at a given point. The depth of the defense should prevent the enemy from rapidly exploiting its success. It also defuses the enemy‘s combat power by forcing the enemy to contain bypassed friendly defensive positions in addition to continuing to attack positions in greater depth.
    3-148. This form of defense may be used when defensible terrain is available in the forward portion of the platoon's area of operation, or to take advantage of a major linear natural obstacle. It also is used when the enemy is mainly Infantry; the platoon conducts a security mission such as counter infiltration, or as directed by company. This technique allows interlocking and overlapping observation and fields of fire across the platoon's front. (See figure 3-12.) The bulk of the platoon's combat power is well forward. Sufficient resources must be available to provide adequate combat power to detect and stop an attack. The platoon relies on fighting from well-prepared mutually supporting positions. It uses a high volume of direct and indirect fires to stop the attacks. The main concern when fighting this form of defense is the lack of flexibility and the difficulty of both seizing the initiative and seeking out enemy weaknesses. Obstacles, indirect fires, and contingency plans are vital to this maneuver. The platoon depends upon surprise, well-prepared positions, and deadly accurate fires to defeat the enemy. The reserve is usually small, perhaps a squad.
    Figure 3-12. Platoon defense of a linear obstacle
    3-149. Minefields and other obstacles are positioned and covered by fire to slow the enemy and inflict casualties. Engaging the enemy at long range by supporting fires (CAS, attack helicopters, and field artillery) disrupts the momentum of his the attack. Use fires from mortars, machine guns, and small arms as he comes into range. If the defense is penetrated, block the advance with the reserve and shift fire from the forward squads onto the enemy flanks. Then, counterattack with the platoon reserve or the least committed squad with intense fires. The purpose is to destroy isolated or weakened enemy forces and regain key terrain.
    Soldier with the M240L Lightweight Medium Machine Gun.
    3-150. The counterreconnaissance effort is critical when fighting to deny the enemy the locations of the platoon's forward positions. If the enemy locates the forward positions, he will concentrate combat power where he desires while fixing the rest of the platoon to prevent their maneuver to disrupt his attack. This effort might be enhanced by initially occupying and fighting from alternate positions forward of the primary positions. This tactic enhances the security mission and deceives the enemy reconnaissance that may get through the security force.
  22. --Perimeter Defense

    3-151. The platoon leader can employ the perimeter defense as an option when conducting an area or mobile defense. A perimeter defense is a defense oriented in all directions. (See figure 3-13.) The Infantry platoon uses it for self-security, and to protect other units located within the perimeter. The platoon can employ a perimeter defense in urban or woodland terrain. The platoon might be called upon to execute the perimeter defense under a variety of conditions, including ─
    When it must secure itself against terrorist or insurgent attacks in an urban area. This technique also may apply if the platoon must conserve or build combat power in order to execute offensive tasks or patrolling missions. When it must hold critical terrain in areas where the defense is not tied in with adjacent units. When it has been bypassed and isolated by the enemy and must defend in place. When it conducts occupation of an independent assembly area or reserve position. When it begins preparation of a strongpoint. When it is directed to concentrate fires into two or more adjacent avenues of approach. Figure 3-13. Platoon perimeter defense
    Soldiers establish a security perimeter.
    3-152. The Infantry platoon prepares a perimeter defense when there are no friendly units adjacent to it. A perimeter defense might be used in a reserve position, in an AA or patrol base, on a follow-on decentralized platoon operation during resupply or when the platoon is isolated. The following actions constitute setting up a perimeter defense ─
    Preparing a perimeter defense is like preparing any other position defense, but the platoon must disperse in a circular configuration for all-round security. (The actual shape depends on the terrain.) The platoon must be prepared to defend in all directions. The platoon leader assigns squads to cover the most likely approach, and prepares alternate and supplementary positions within the perimeter. Javelins cover likely armor approaches. They may use hide positions and move forward to fire as the enemy appears. The platoon leader assigns several firing positions. If there are few positions for them, they are assigned a primary position and are dug in. Snipers or designated marksman should cover likely or suspected enemy positions or observation posts. Snipers and designated marksmen also should be used to observe or overwatch areas where civilians congregate. Keep attached mortars near the center of the perimeter so their minimum range does not restrict their ability to fire in any direction. They should dig in and have covered ammunition storage bunkers. If possible, hold one or more rifle team in reserve. The platoon leader assigns a primary position to the rear of the platoon, covering the most dangerous avenues of approach, and may assign the rifle squad supplementary positions since the platoon is prepared to fight in all directions. Prepare obstacles in-depth around the perimeter. Plan direct and indirect fire as for any type of defense. Plan and use direct and indirect fire support from outside the perimeter when available. Counter enemy probing attacks by area fire weapons (artillery, mortars, claymores, and grenade launchers) to avoid revealing the locations of fighting positions (rules of engagement-dependent). If the enemy penetrates the perimeter, the reserve destroys, and then blocks the penetration. It also covers friendly Soldiers during movement to alternate, supplementary, or subsequent positions. Even though the platoon's counterattack ability is limited, it must strive to restore its perimeter. Sustainment elements may support from within the perimeter or from another position. Supply and evacuation might be by air. Consider the availability of landing zones and drop zones (protected from enemy observation and fire) when selecting and preparing the position. Y-SHAPE VARIATION
    3-153. The Y-shaped perimeter defense is a variation of the perimeter defense that uses the terrain effectively. This defense is used when the terrain, cover and concealment, or fields of fire do not support the physical positioning of the squads in a circular manner. The Y-shaped perimeter defense is so named because the squad’s battle positions are positioned on three different axes radiating from one central point. (See figure 3-14.) It is still a perimeter defense because it is effective against an attack from any direction. The Y-shaped defense provides all-round perimeter fires without having to position Soldiers on the perimeter. It is likely to be most effective in mountainous terrain, but it also may be used in a dense jungle environment due to limited fields of fire. All of the fundamentals of a perimeter defense previously discussed apply, with the following adjustments and special considerations ─
    Although each squad battle position has a primary orientation for its fires, each squad must be prepared to reorient to mass fires into the engagement areas to its rear. When no most likely enemy approach is identified, or in limited visibility, each squad may have half its Soldiers oriented into the engagement areas to the front and half into the engagement areas to the rear. Ideally, supplementary individual fighting positions are prepared, allowing Soldiers to reposition when required to mass fires into one engagement area.
      Figure 3-14. Y-shaped perimeter defense
    When a most likely enemy avenue of approach is identified, the platoon leader may adjust the normal platoon orientations to concentrate fires (see figure 3-15) for the following reasons:
    This entails accepting risk in another area of the perimeter. The platoon security plan should compensate for this with additional observation posts, patrols, or other measures. The positioning of the platoon command post, reserve, or any sustainment assets is much more difficult due to a lack of depth within the perimeter. Figure 3-15. Modified Y-shape perimeter defense
    3-154. The most difficult aspect of the Y-shape perimeter defense is the fire control measures required. To fight this defense without casualties from friendly fire, the leaders must ensure the limits of fire for each weapon do not allow fires into the adjacent squad positions. In a mountainous environment, firing downward into the engagement area may make this simpler. Some measures to consider include —
    Position medium machine guns near the apex of the "Y" to allow a final protective line that covers the platoon front while firing away from the adjacent units. Cover the areas of the engagement areas closest to the apex with Claymores, non-persistent mines, or obstacles to reduce the need for direct fires in these areas. Identify those positions at most risk to friendly fires and prepare the fighting position to protect the Soldier from fires in this direction. The loss of one squad position may threaten the loss of the entire platoon. To prevent this, plan and rehearse immediate counterattacks with a reserve or the least committed platoon. Consider allowing the enemy to penetrate well into the engagement areas and destroy him as in an ambush. Be aware that if a Y-shape defense is established on the prominent terrain feature and the enemy has the ability to mass fires, he may fix the platoon with direct fires and destroy it with massed indirect fires.
  23. --Reverse Slope Defense

    3-155. An alternative to defending on the forward slope of a hill or a ridge is to defend on a reverse slope. (See figure 3-16.) In such a defense, the Infantry platoon is deployed on terrain that is masked from enemy direct fire and ground observation by the crest of a hill. Although some units and weapons might be positioned on the forward slope, the crest, or the counter-slope (a forward slope of a hill to the rear of a reverse slope), most forces are on the reverse slope. The key to this defense is control the crest by direct fire.
    Figure 3-16. Platoon defense on a reverse slope
    3-156. Planning fundamentals to a defense on a reverse slope include ─
    Positioning forward squads so they block enemy approaches and exploit existing obstacles. Plans should- Permit surprise fire on the crest and on the approaches around the crest. Have rear and overhead cover to protect friendly Soldiers from fratricide while in forward fighting positions. Positioning observation posts, on the crest or the forward slope of the defended hill. Plans should- Increase observation posts and patrols to prevent infiltration at night. Consider attaching medium machine guns to observation posts. Positioning the squad in-depth or reserve where it can provide the most flexibility, support the forward squads by fire, protect the flanks and the rear of the platoon, and counterattack, if necessary. It might be positioned on the counterslope to the rear of the forward squad if that position allows it to fire and hit the enemy when he reaches the crest of the defended hill. Positioning the platoon command post to the rear where it will not interfere with the reserve or supporting units. Plans should consider that— The platoon leader may have an observation post on the forward slope or crest and another on the reverse slope or counterslope. The observation post is used on the forward slope or crest before the battle starts when the platoon leader is determining the enemy's intentions. During the fight, he moves the observation post on the reverse slope or counterslope. Planning indirect fire well forward of, on, and to the flanks of the forward slope, crest, reverse slope, and counterslope. Planning direct final protective fires on the crest of the hill to control the crest and stop assaults. Reinforcing existing obstacles. Knowing that protective obstacles on the reverse slope―just down from the crest where it can be covered by fire―can slow the enemy's advance and hold him under friendly fire. Knowing that the platoon leader normally plans for counterattacks and plans to drive the enemy off the crest by fire, if possible. Knowing that the platoon leader also is prepared to drive the enemy off by fire and movement. EMPLOYMENT
    3-157. The Infantry leader can adopt a reverse slope position when ─
    Enemy fire makes the forward slope untenable. Lack of cover and concealment on the forward slope makes it untenable. The forward slope has been lost or not yet been gained. The forward slope is exposed to enemy direct fire weapons fired from beyond the effective range of the defender's weapons. Moving to the reverse slope removes the attacker's standoff advantage. The terrain on the reverse slope provides better fields of fire than the forward slope. Surprising and deceiving the enemy as to the true location of the Infantry platoon’s defensive positions is essential. Enemy weapons systems have overmatch in range and lethality. 3-158. When executing a reverse slope defense, the leader places special emphasis on ─
    A direct and indirect fire support plan to prevent the enemy’s occupation and using crest of the hill. The use of observation posts or reconnaissance elements on the forward slope to provide observation across the entire front and security to the main battle positions. A counterattack plan specifying measures necessary to clear the crest or regain it from the enemy. Direct and indirect fire support to destroy disrupt, and attrition of enemy forces on the forward slope. 3-159. The forward edge of positions should be within small arms range of the crest. It should be far enough from the crest, which fields of fire, allow the defender time to place well-aimed fire on the enemy before he reaches friendly positions. The platoon establishes observation posts on or forward of the topographical crest. This allows long-range observation over the entire front and indirect fire coverage of forward obstacles. Observation posts usually are provided by the unit owning the terrain being observed, and may vary in size from a few Soldiers to a reinforced squad. They should include forward observers. At night, their number should be increased to improve security.
    3-160. These are some considerations leaders may apply when defending on a reverse slope ─
    Observation of the enemy is more difficult. Soldiers in this position see forward no farther than the crest. This makes it hard to determine exactly where the enemy is as he advances, especially when visibility is poor. Observation posts must be placed forward of the topographic crest for early warning and long-range observation. Egress from the position might be more difficult. Fields of fire are usually short. Obstacles on the forward slope can be covered only with indirect fire or by units on the flanks of the company unless some weapons systems are placed forward initially. If the enemy gains the crest, he can assault downhill. This may give him a psychological advantage. If observation posts are insufficient or improperly placed, the defenders might have to fight an enemy who suddenly appears in strength at close range. A reverse slope engagement is decisive resulting in one or both forces being severely attritted. Very difficult to break contact. Placing the vehicles at the bottom of the hill and the infantry on counter slope allows the platoon to maximize its firepower into the engagement area as the enemy crests the slope. The defender often has the opportunity to take the first shot at the attacker.
  24. *****Fighting Positions*****

    3-161. The defensive plan normally requires building fighting positions. The mechanized platoon uses fighting positions for its dismounted Infantrymen and for its BFV - bradley fighting vehicle
  25. --Dismounted

    3-162. Fighting positions protect Soldiers by providing cover from direct and indirect fires and concealment through positioning and proper camouflage. Because the battlefield conditions confronting Soldiers are never standard, no single standard fighting position design fits all tactical situations.
    3-163. Refer to TC 3-21.75 for details on the construction of ─
    Hasty fighting positions. Fighting positions for crew-served weapons, to include machine guns and Javelins. Fighting positions for one, two, and three men. Shoulder-launched munitions positions.
  26. --Mounted

    3-164. Vehicles use natural cover and concealment in hide positions initially to increase survivability. As time, assets, and situations permit, positions are prepared using organic excavation equipment or engineer support. Priority is given to those vehicles containing essential equipment or supplies. Crews use these fighting positions for individual protection as well.
    3-165. Parapets positioned at the front of or around major weapon systems provide improved protection from direct fire and from blast and fragments of indirect fire, artillery, mortar, and rocket shells. At its base, the parapet should be at least 8 feet thick. The parapet functions as a standoff barrier for impact-detonating direct fire high explosive antitank and ATGM projectiles. The parapet should cause the fuzes to activate, thereby increasing survivability for the protected vehicles. If the enemy uses kinetic energy, direct fire armor-piercing, or hypervelocity projectiles, it is impractical to construct parapets thick enough for protection. To protect against these projectiles, deep-cut, hull defilade, or turret defilade positions are prepared. Fighting and protective positions for essential vehicles should be constructed no larger than needed.
    3-166. Success in the area of operation requires maneuver between fighting positions between main gun firings. Maximum use of terrain is required to conceal fighting vehicles maneuvering between fighting positions. After a major weapon system fires its main gun, the vehicle should move concealed to another position before firing again. If the major weapon system immediately reappears in the old position, the enemy knows where to fire his next round.
    3-167. Hasty fighting positions for combat vehicles, to include armored personnel carriers and mortar carriers, take advantage of natural terrain features. These positions are prepared with at least construction effort. A frontal parapet, as high as practical without interfering with the vehicle’s weapon systems, shields the position from frontal attack and provides limited concealment if properly camouflaged. Protection is improved if the position is made deeper and the parapet extended around the vehicle’s sides. Parapets provide a false sense of security against kinetic energy and hypervelocity projectiles; therefore, hasty vehicle fighting positions with parapets are not recommended for vehicles Hasty fighting positions offer protection from HE antitank projectiles and provide limited concealment if properly camouflaged. As the tactical situation permits, hasty positions are improved to deliberate positions.
    3-168. Deliberate fighting positions must protect a vehicle from kinetic energy and hypervelocity projectiles. The position is constructed in four parts: hull defilade, concealed access ramp or route, hide location, and turret defilade. (See figures 3-17 and 3-18.)
    Figure 3-17. Developing deliberate fighting positions
    Figure 3-18. Top view of Y-shaped fighting position
    3-169. Positions formed by natural terrain are usually best because they are easy to modify. If preparation is necessary, extensive engineer support is required. Each position is camouflaged with either natural vegetation or a camouflage net, and the spoil is flattened out or hauled away. All fighting positions for fighting vehicles (tanks and BFVs) are planned as deliberate positions. Since the lack of time usually does not allow full construction of a deliberate position, only some parts of the position are prepared. For example, the complete fighting position for a BFV requires the construction of a hull defilade, turret defilade, concealed access ramp or route, and hides location all within the same position. The maneuver team commander uses organic and engineer earthmoving assets and usually constructs part of the fighting position.
    3-170. Digging hide locations and concealed routes between fighting positions is normally not practical due to the lack of engineer assets and time. Engineer assets are used to dig the hull and turret defilade positions. The ramps and concealed routes require only partial clearing and leveling with blade tanks or engineer equipment because natural concealed routes and hide locations are used. If time permits, the commander expands the fighting position to all four parts, to include a hide and turret defilade location. The access ramp from the hide location to the hull defilade position usually provides turret defilade for a vehicle at some point on the ramp. This location can be marked with engineer tape and a chemical light so the driver knows when to stop.
  27. *****Engagement Area Development*****

    3-171. The engagement area is where the Infantry leader intends to engage and destroy an enemy force using the massed fires of all available weapons. Leaders combine natural and man-made obstacles to canalize the attacking force into engagement area. The success of engagements depends on how the leader can integrate the obstacle plan, indirect fire plan, and direct fire plan within the engagement area to achieve the Infantry platoon’s and squads’ tactical purposes.
    3-172. At the platoon level, engagement area development is a complex function demanding parallel planning and preparation if the Infantry platoon and squad are to accomplish the myriad tasks for which it is responsible. Despite this complexity, engagement area development resembles a drill, and the platoon leader and his subordinate leaders use an orderly, standard set of procedures. The steps of engagement area development are not a rigid sequential process. Some steps may occur simultaneously to ensure the synergy of combined arms. Beginning with evaluation of METT-TC, the development process —
    Identifies all likely enemy avenues of approach. Determines likely enemy schemes of maneuver. Determines where to kill the enemy. Plans and integrates obstacles. Emplaces weapon systems. Plans and integrates indirect fires. Rehearses the execution of operations in the engagement area.
  28. --Identify Likely Enemy Avenues of Approach

    Soldier keeping watch over a possible enemy avenue of approach.
    3-173. Procedures and considerations when identifying the enemy's likely avenues of approach (see figure 3-19) include —
    Conducting initial reconnaissance. If possible, do this from the enemy's perspective along each avenue of approach into the area of operations or engagement area. Identifying key and decisive terrain. This includes locations affording positions of advantage over the enemy, as well as natural obstacles and choke points restricting forward movement. Determining which avenues provide cover and concealment for the enemy while allowing him to maintain his tempo. Determining what terrain the enemy is likely to use to support each avenue. Evaluating lateral routes adjoining each avenue of approach. Figure 3-19. Likely enemy avenues of approach
  29. --Determine the Enemy Scheme of Maneuver

    General Krueger, Rupertus and MacArthur discuss the proposed scheme of maneuver for Cape Gloucester at the 1st Marine Division CP, 14 December 1943.
    3-174. Procedures and considerations in determining the enemy’s scheme of maneuver (see figure 3-20) include —
    Determining how the enemy will structure the attack. Determining how the enemy will use his reconnaissance assets. Will he attempt to infiltrate friendly positions? Determining where and when the enemy will change formations and establish support-by-fire-positions. Determining where, when, and how the enemy will conduct his assault or breaching operations. Determining where and when he will commit follow-on forces. Determining the enemy’s expected rates of movement. Assessing the effects of his combat multipliers and anticipated locations/areas of employment. Determining what reactions, the enemy is likely to have in response to projected friendly actions. Figure 3-20. Example of an enemy scheme of maneuver
  30. --Determine Where to Kill the Enemy

    3-175. The following steps apply in identifying and marking where the enemy engagement (see figure 3-21) is to occur ─
    Identify target registration points matching the enemy’s scheme of maneuver allowing the Infantry platoon and squad to identify where it will engage enemy forces through the depth of the area of operations. Identify and record the exact location of each target registration point. In marking target registration points, use thermal sights to ensure visibility at the appropriate range under varying conditions, including daylight and limited visibility (darkness, smoke, dust, or other obscurants) Determine how many weapon systems will focus fires on each target registration point to achieve the desired end state. Determine which element will mass fires on each target registration point. Establish engagement areas around target registration points. Develop the direct fire planning measures necessary to focus fires at each target registration point. Figure 3-21. Locations to kill enemy
    The following video shows Apache helicopters destroying enemy fighting positions above the village of Donga, Afghanistan. The positions were discovered a day earlier during an ambush of a patrol conducting a key leader engagement. With help from a forward observer, the helicopters identified the targets, ensuring no civilians were present and then destroyed the positions using their 30 mm cannon and rockets.
  31. --Plan and Integrate Obstacles

    3-176. The following steps apply in planning and integrating obstacles (see figure 3-22) during defensive missions ─
    Determine the obstacle group intent with the engineer platoon leader confirming the target, relative location, and effect. Ensure intent supports the task force scheme of maneuver. In conjunction with the engineer platoon leader, identify, site, and mark the obstacles within the obstacle group. Integrate protective obstacle types and locations within Infantry platoon defensive perimeter. Ensure coverage of all obstacles with direct fires and or indirect fires. Assign responsibility for guides and lane closure as required. According to METT-TC, assist engineer platoons in emplacing obstacles, securing Class IV/V point, and securing obstacle work sites. Coordinate engineer disengagement criteria, actions on contact, and security requirements with the engineer platoon leader at the obstacle work site. Figure 3-22. Plans for and integration of obstacles
  32. --Emplace Weapon Systems

    3-177. The following steps apply in selecting and improving battle positions and emplacing the Infantry platoon and squad vehicles, crew-served weapon systems, (see figure 3-23) and dismounted Infantry positions ─
    Select tentative platoon/squad battle positions. Note. When possible, select battle positions while moving in the engagement area. Using the enemy’s perspective enables the Infantry leader to assess survivability of positions.
    Conduct a leader’s reconnaissance of the tentative battle positions. Drive the engagement area to confirm selected positions are tactically advantageous. Confirm and mark the selected battle positions. Ensure battle positions do not conflict with those of adjacent units and are tied in with adjacent positions. Select primary, alternate, and supplementary fighting positions to achieve the desired effect for each target registration point. Ensure platoon sergeants, vehicle commanders, or dismounted Infantry squad leaders position weapon systems so each target registration point is covered by the required number of weapons, vehicles, and squads. Ensure positions allow vehicle commanders, loaders, and gunners (as applicable for each vehicle or weapons system) to observe the engagement area and engage enemy forces from the hull down position. Stake vehicle or weapons system positions according to unit SOPs so engineers can dig in the positions while vehicle crews perform other tasks. Confirm all vehicle or weapons system positions.  
    Figure 3-23. Emplacement of weapons systems
  33. --Plan and Integrate Indirect Fires

    3-178. The following steps apply in planning and integrating indirect fires (See figure 3-24) ─
    Determine the purpose of fires. Determine where purpose will best be achieved. Establish the observation plan that includes- Redundancy for each target. Observers who will include the fire support team, as well as members of maneuver elements with direct fire support execution responsibilities. Establish triggers based on enemy movement rates. Obtain accurate target locations using organic target location devices or survey/navigational equipment. Refine target locations to ensure coverage of obstacles. Plan final protection fire. Request critical friendly zone for protection of maneuver elements and no-fire areas for protection of observation posts and forward positions. Figure 3-24. Integration of direct and indirect fires
    Watch the following video to learn more about indirect fires.
  34. --Rehearals

    3-179. The purpose of rehearsals is to ensure every leader and Soldier understands the plan and elements are prepared to cover their assigned areas with direct and indirect fires. The rehearsal should cover ─
    Rearward passage of security forces (as required). Closure of lanes (as required). Movement from the hide position to the battle position. Use of fire commands, triggers, and maximum engagement lines (MELs) to initiate direct and indirect fires. Shifting of fires to refocus and redistribute fire effects. Disengagement criteria. Identification of displacement routes and times. Disengagement criteria. Preparation and transmission of critical reports using radio and digital systems (as applicable). Assessment of the effects of enemy weapon systems. Displacement to alternate, supplementary, or subsequent battle positions. Cross-leveling or resupply of Class V. Evacuation of casualties. 3-180. The platoon leader should coordinate rehearsals with higher headquarters to ensure there are no conflicts with other units. Coordination leads to efficient use of planning and preparation time for all units involved with the operation. It eliminates dangers of misidentifying friendly forces in the rehearsal area, which could result in fratricide.
    The following video shows Engagement Area Development in a Urban Area.
  35. *****Transitions*****

    3-181. During the planning for operations, the Infantry leader must discern from the higher headquarters OPORD what the potential follow-on missions are and begin to plan how they intend to achieve them. During this planning, the leader determines the possible timeline and location for consolidation and reorganization best facilities future operations and provides adequate protection.
  36. --Consolidation

    3-182. Small unit leaders plan and prepare for consolidation during TLP. The following actions are usually a part of consolidation ─
    Eliminate enemy resistance on the objective. Establish security beyond the objective by securing areas that may be the source of enemy direct fires or enemy artillery observation. Establish additional security measures such as observation posts and patrols. Prepare for and assist the passage of follow-on forces (if required). Continue to improve security by conducting other necessary defensive actions. These defensive actions include engagement area development, direct fire planning, and battle position preparation. Adjust final protective fires and register targets along likely mounted and dismounted avenues of approach. Protect the obstacle reduction effort. Secure detainees. Prepare for enemy counterattack. The following vignette describes a consolidation during the Vietnam campaigns. ─
  37. --Reorganization

    3-183. Reorganization usually is conducted concurrently with consolidation. It consists of actions taken to prepare the unit for follow-on tasks. As with consolidation, small unit leaders plan and prepare for reorganization during TPL - Troop Leading Procedures. During reorganization, the small unit leader ensures the following actions are taken ─
    Provide essential medical treatment and evacuate casualties as necessary. Treat and evacuate wounded detainees and process the remainder of detainees. Cross-level personnel and adjust task organization as required to support the next phase or mission. Conducts resupply operations, including rearming and refueling. Redistribute ammunition. Conduct required maintenance. Continue improving defensive positions as necessary.
  38. --Continuing Operations

    3-184. At the conclusion of an engagement, the Infantry platoon may continue the defense, or if ordered, transition to the offense or stability. The platoon leader considers the higher commander’s concept of the operation, friendly capabilities, and enemy situation when making this decision. All missions should include plans for exploiting success or assuming a defensive posture.
    3-185. A defending unit may transitions from defensive tasks to the retrograde as a part of continuing operations. A retrograde usually involves a combination of a delay, withdrawal, and retirement that may occur simultaneously or sequentially. As in other missions, the leader’s concept of the operation and intent drive planning for the retrograde. Each form of retrograde has its unique planning considerations, but considerations common to all retrogrades are risk, the need for synchronization and security.
  39. --Transition to the Offense

    3-186. A company commander may order a defending Infantry platoon to conduct a hasty operation or participate in a movement to contact. As part of a reserve force, the Infantry platoon and squad may execute a counterattack to destroy exposed enemy elements and free decisively engaged friendly elements. A base-of-fire element suppresses or fixes the enemy force while the counterattack (maneuver) element moves on a concealed route to firing positions from which it can engage the enemy in the flank and rear. The counterattack element must maneuver rapidly to its firing position, often fighting through enemy flank security elements, to complete the counterattack before the enemy can bring follow-on forces forward to influence the fight.
    3-187. Execution of the counterattack is similar to an assault by fire. Planning and preparation considerations for counterattack vary depending on the purpose and location of the operation. For example, the counterattack may be conducted forward of friendly positions, requiring the reserve force to move around friendly elements and through their protective and tactical obstacles. In other situations, the Infantry leader may use a counterassault by fire to block, fix, or contain a penetration. In any case, the reserve force conducts the counterattack as an enemy-oriented task.
  40. --Transition to Stability

    3-188. It may be tactically wise for the leader to plan a defensive contingency with on-order offensive tasks for operations focused on stability tasks. Subordinate leaders must be fully trained to recognize activities, which initiate this transition. Leaders and Soldiers must be aware that elements of the BCT - Brigade Combat Team could be conducting offensive, defensive, and stability missions simultaneously within a small radius of each other. Actions in one unit’s area of operation can affect a change in whatever type task an adjacent unit is conducting. For example, an engagement with an enemy force may have caused noncombatants to be displaced to another section of the city leaving the area of operation open to theft, looting, and vandalism by belligerents.
    US Forces-Iraq transitioned from counterinsurgency (COIN) to stability operations during the period 1 January 2009 (the signing of the Security Agreement) through 31 August 2010 (the end of combat operations). The following report documents the transition to stability operations in Iraq. - LINK