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.
BATTLE HANDOVER LINE
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 ─
3-62. Primary positions cover the enemy’s most likely avenue of approach into the area. (See figure 3-7.)
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.
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.
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
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
FORWARD EDGE OF THE BATTLE AREA
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.
MAIN BATTLE AREA
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.