text: Sustainment Operations During Armed Conflict
  since the enemy typically has the initiative. As a result, sustainment organizations and the functions they
  execute play a critical role in supporting the defense and the success of subsequent future operations.
  5-143. There are three types of defensive operations: area defense, mobile defense, and retrograde. An area
  defense orients on retaining terrain and denying enemy forces access to desired terrain while not destroying
  the enemy outright. A mobile defense defeats the attacking forces by permitting the enemy to advance into a
  position that exposes them to counterattack. A retrograde moves the friendly forces away from the enemy to
  gain time, preserve forces, place the enemy in unfavorable positions, or avoid combat under undesirable
  conditions.
  5-144. Defending commanders combine the three types of defensive operations to fit the situation. All three
  types of defenses use mobile and static elements. In mobile defenses, static positions help control the depth
  and breadth of the enemy penetration and retain ground from which to launch counterattacks. In area
  defenses, commanders closely integrate patrols, security forces, and reserve forces to cover gaps among
  defensive positions. Commanders reinforce positions as necessary and counterattack as directed. In
  retrograde operations, some units conduct area or mobile defenses or security operations to protect other units
  that execute carefully controlled maneuver or movement rearward. These units use static elements to fix,
  disrupt, turn, or block the attackers. Mobile elements are used to counterattack and destroy the enemy.
  5-145. Commanders execute defensive operations for various reasons, such as to retain decisive terrain or
  deny a vital area to the enemy, weaken or fix the enemy as a prelude to offensive actions, or increase the
  enemy’s vulnerability by forcing the enemy to concentrate subordinate forces. The ultimate purpose of the
  defense is to create conditions for a counteroffensive whereby it allows Army forces to regain the initiative.
  SUSTAINMENT FUNDAMENTALS FOR DEFENSIVE OPERATIONS
  5-146. Enemy commanders look for opportunities to counter corps and division defensive operations. The
  enemy will seek to employ special purpose forces, irregular forces, electronic warfare, long-range artillery,
  rockets, missiles, information capabilities, and cyberspace electromagnetic activities to disrupt sustainment
  activities. The enemy may exploit use of electromagnetic signals such as cell phones and geotagged photos
  to assist in targeting of sustainment units and locations. Sustainment commanders must be aware of these
  unintended threats and focus on those efforts that would help set the conditions necessary to regain the
  initiative during defensive operations.
  5-147. All sustainment functions are planned and executed to support defensive operations and build combat
  power to prepare for future offensive operations. The exact type and extent of support operations and the
  organizations executing them will vary by echelon based on the support requirement. Even though defensive
  operations may be the main effort, simultaneous offensive operations with their support requirements are also
  likely to be ongoing.
  5-148. Sustainment commanders and staffs plan for increased requirements in Class IV, V, VIII, and IX items
  to support the defensive effort and build Class III (bulk and package) and Class V stocks to prepare to
  transition to offensive operations. Sustainment planners anticipate where the greatest need might occur during
  operations and consider pre-positioning sustainment stocks far forward to reduce response times for critical
  support. Planners also consider alternative methods for delivering sustainment in emergencies. Sustainment
  of defensive operations requires a coordinated planning effort designed to maximize synchronization,
  integration, and continuity of support at all echelons. Commanders and staffs at every echelon must anticipate
  operational requirements, be responsive in requisitioning and distributing resources, and be prepared to
  improvise tactics and techniques for execution that ensure responsiveness, even in unexpected situations.