Infantry Drills

H-8: Constructed Obstacles

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H-8. Units create constructed obstacles with manpower or equipment without the use of explosives. Examples of constructed obstacles include:

  • Ditches. Ditches across roads and trails are obstacles. Large ditches in open areas require engineer equipment.
  • Log hurdles. Log hurdles act as “speed bumps” on roads. They are installed easily and are most effective when used in conjunction with other obstacles.
  • Log cribs. A log crib is constructed of logs, dirt, and rocks. The logs are used to make rectangular or triangular cribs filled with dirt and rock.
    • These are used to block narrow roads and defiles. Unless substantially built, log cribs will not stop tanks.
  • Log posts. Log posts embedded in the road and employed in-depth can stop tracked vehicles. If they are not high enough to be pushed out of the way, posts can cause a tracked vehicle to throw a track if it tries to climb over. If employed with wire and mines, they also can slow enemy Infantry.
  • Wire entanglements. Wire entanglements impede the movement of dismounted enemy Infantry, and in some cases, tracked and wheeled vehicles.
    • Triple standard concertina is a common wire obstacle. However, there are other types, such as double apron, tanglefoot, and general-purpose barbed-tape obstacles.
    • Figures H-2a through H-2c (pages H-5 through H-6) illustrate examples of wire and log obstacles. The materials used in constructing wire entanglements are relatively lightweight (compared to other obstacles) and inexpensive, considering the protection they afford.
Figure H-2a. Constructed wire and log obstacles
Figure H-2b. Constructed wire and log obstacles
Figure H-2c. Constructed wire and log obstacles

Next: H-9: Demolition Obstacles

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