Infantry Drills

3-23: Mobile Defense



Previous: 3-21: 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.

Next: 3-26: Retrograde

Go Back To: U.S. Army FM 3-21.8: The Infantry Rifle Platoon and Squad