text: FM 7-100.1________________________________________________________________________________
  Method
  4-114. Area defense inflicts losses on the enemy, retains ground, and protects
  friendly forces. It does so by occupying battle positions in complex terrain and
  dominating the surrounding battlespace with reconnaissance fire (see
  Chapter 7). These fires attack designated elements of the enemy’s combat
  system to destroy components and subsystems that create an advantage for the
  enemy. The operational design of an area defense is to begin disaggregating
  the enemy’s combat system in the disruption zone. When enemy forces enter
  the battle zone, they should be incapable of synchronizing combat operations.
  4-115. Area defense creates windows of opportunity in which to conduct
  spoiling attacks or counterattacks and destroy key enemy systems. In the
  course of an area defense, the operational-level commander uses terrain that
  exposes the enemy to continuing attack.
  4-116. An area defense trades time for the opportunity to attack enemy forces
  when and where they are vulnerable. The OPFOR might use an area defense
  when
  • It is conducting access-control operations.
  • Enemy forces enjoy a significant RISTA and precision standoff advantage.
  • Conditions are suitable for canalizing the enemy into areas where the
  OPFOR can destroy him by fire and/or maneuver.
  4-117. A skillfully conducted area defense can allow a significantly weaker force
  to defeat a stronger enemy force. However, the area defense relies to a significant
  degree on the availability of complex terrain and decentralized logistics. Units
  conducting an area defense typically place small ambushing and raiding
  forces in complex terrain throughout the AOR to force the enemy into
  continuous operations and steadily drain his combat power and resolve.
  4-118. Within an overall operational area defense, the OPFOR might use
  maneuver defense on some portions of the AOR, especially on those where it
  can afford to lose ground. This occurs most often during transition operations
  as forces initially occupy the complex terrain positions necessary for the
  execution of the area defense.
  Disruption Force
  4-119. In an area defense, the disruption zone is that battlespace surrounding
  its battle zone(s) where the OPFOR may cause continuing harm to the enemy
  without significantly exposing itself. For example, counterreconnaissance ac-
  tivity may draw the attention of enemy forces and cause them to enter the
  kill zone of a sophisticated ambush using long-range precision fires. RISTA
  assets and counterreconnaissance forces occupy the disruption zone, along
  with affiliated forces. Paramilitary forces may assist other disruption force
  units by providing force protection, controlling the civilian population, and
  executing deception operations as directed.
  4-120. The disruption zone of an area defense is designed to be an area of un-
  interrupted battle. OPFOR RISTA maintains contact with enemy forces, and
  other parts of the disruption force attack them incessantly with ambush and
  precision fires.