text: FM 7-100.1________________________________________________________________________________
  4-17. Adaptive operations are often sanctuary-based. Sanctuaries are areas
  that limit the ability of an opponent to apply his full range of capabilities.
  The OPFOR can use physical and/or moral sanctuaries for preserving and
  applying forces. It can defend in sanctuaries or attack out of them. It may
  conduct limited-objective attacks from these positions to prevent buildup
  of intervening forces, to facilitate the defense, or to take advantage of an
  opportunity to counterattack. When defending, the OPFOR generally does
  not employ fixed, contiguous defensive fronts.
  4-18. The OPFOR uses flexible and unpredictable force structures task-
  organized for particular missions. Forces may be combined arms, joint,
  interagency, and possibly multinational. The State may fully mobilize all
  available means to create large conventional force and paramilitary capability in
  support of adaptive operations. Full mobilization involves all military and
  paramilitary forces, including militia. During adaptive operations, the
  State will use conventional forces in adaptive ways. It will also employ
  unconventional and specialized forces tailored to the needs of combat against
  an extraregional force with technological overmatch. Operations may also
  involve various types of affiliated forces.
  PURPOSE OF THE DEFENSE
  4-19. Defensive operations are designed to achieve the goals of the strategic
  campaign through active measures while preserving combat power. However,
  the purpose of any given defensive operation depends on the situation.
  4-20. The primary distinction among types of OPFOR defensive operations is
  their purpose. Therefore, the OPFOR recognizes three general types of defen-
  sive operations according to their purpose: to destroy, preserve, or deny.
  DEFENSE TO DESTROY
  4-21. A defense to destroy is designed to eliminate an attacking formation’s
  ability to continue offensive operations while preserving friendly forces and
  setting the military conditions for a favorable political settlement. Such a
  defense may be the entirety of an operation or may be used to defeat a
  counterattack during a larger OPFOR offensive action. An operational
  defense to destroy often has one or more tactical offensive actions as
  subcomponents.
  DEFENSE TO PRESERVE
  4-22. A defense to preserve is designed to protect key components of the
  OPFOR from destruction by the enemy. Such a defense may occur
  • To preserve combat power for future operations.
  • Before the outbreak of a war, or in its early stages, to cover the mobili-
  zation and deployment of the main forces.
  • When facing numerically or qualitatively superior enemy forces.
  • During an offense, to economize force in one area and achieve superior-
  ity in another.