Infantry Drills

3-152: Preparations

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Previous: 3-151: Perimeter Defense

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.

Next: 3-153: Y-Shape Variation

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