ADP 3-90, page 64

Chapter 4 4-4 ADP 3-90 31 July 2019  A delay is when a force under pressure trades space for time by slowing down the enemy’s momentum and inflicting maximum damage on enemy forces without becoming decisively engaged. In delays, units yield ground to gain time while retaining flexibility and freedom of action to inflict the maximum damage on enemy forces.  Withdraw is to disengage from an enemy force and move in a direction away from the enemy. Withdrawing units, whether all or part of a committed force, voluntarily disengage from an enemy force to preserve the withdrawing force or release it for a new mission.  A retirement is when a force out of contact moves away from the enemy. In each variation of a retrograde, a force not in contact with an enemy force moves to another location, normally by a tactical road march. In all variations of the retrograde, firm control of friendly maneuver elements is a prerequisite for success. COMMON DEFENSIVE CONTROL MEASURES 4-21. Commanders control a defense by using control measures that provide the flexibility needed to allow defending commanders to concentrate combat power at the decisive point. They can use battle positions, direct fire control, and FSCMs in addition to other control measures to synchronize the employment of combat power. Commanders designate disengagement lines to trigger the displacement of subordinate forces. BATTLE POSITIONS 4-22. A battle position is a defensive location oriented on a likely enemy avenue of approach. A battle position is not an AO. Battle positions symbols depict the locations and general orientations of defending ground maneuver forces. A commander’s use of a battle position does not direct a subordinate to position that subordinate’s entire force within its bounds. Units as large as battalion task forces and as small as squads or sections use battle positions. Commanders select positions based on terrain, enemy capabilities, and friendly capabilities. Commanders assign some or all subordinates battle positions. The unit occupying the battle position prepares fighting and survivability positions for its weapons systems, vehicles, Soldiers, and supplies to accomplish its mission. 4-23. Commanders assign subordinates to battle positions in situations when friendly forces need to retain a greater degree of control than that provided through only using an AO. This greater degree of control occurs because a commander controls maneuver outside the general location of the battle position. Multiple battle positions may be assigned to a single unit, which allows that unit to maneuver between battle positions. Commanders specify mission and engagement criteria to the unit assigned to a battle position. Security, supporting artillery, and sustainment forces typically operate outside a unit’s battle position. Units occupying a battle position do not automatically have all the doctrinal responsibilities associated with being assigned an AO. 4-24. Units occupy or displace from battle positions as part of the overall plan. The commander assigning a unit to a battle position specifies when and under what conditions the unit displaces from the position. If a unit is ordered to defend a battle position, its commander has the option of moving off the battle position. If that unit is directed to retain a battle position, its commander needs to know the specific conditions that must exist before the unit can displace. 4-25. There are five kinds of battle positions:  The primary position is the position that covers the enemy’s most likely avenue of approach into the area of operations. It is the best position from which to accomplish the defensive mission, such as the overwatch of an engagement area to prevent enemy penetration.  An alternate position is a defensive position that the commander assigns to a unit or weapon system for occupation when the primary position becomes untenable or unsuitable for carrying out the assigned task. The unit commander locates alternate positions so the occupants can continue to fulfill the original task, such as covering the same avenue of approach or engagement area as the primary position. These positions increase a defending force’s survivability by allowing the defending force to engage the enemy force from multiple positions.