Infantry Drills

3-19: Defense In-Depth

Previous: 3-18: Forms of Defensive Maneuver

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.

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.
Figure 3-1. Platoon defense in-depth

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