text: Operations During Armed Conflict
  positions and focus their fires into engagement areas. Units may supplement these fires with a possible
  counterattack. Units at all echelons can conduct an area defense, and Army forces may have maritime
  engagement areas. They may use an area defense to transition to offensive operations, retrograde operations,
  or stability operations. (See ADP 3-90 for more information on area defense.)
  MOBILE DEFENSE
  6-188. A mobile defense is a type of defensive operation that concentrates on the destruction or defeat of
  the enemy through a decisive attack by a striking force (ADP 3-90). The mobile defense focuses on defeating
  or destroying enemy forces by allowing them to advance to a point where they are exposed to a decisive
  counterattack by a striking force. The striking force is a dedicated counterattack force in a mobile defense
  constituted with the bulk of available combat power (ADP 3-90). A fixing force is a force designated to
  supplement the striking force by preventing the enemy from moving from a specific area for a specific time
  (ADP 3-90). The fixing force is used to hold attacking enemy forces in position, to turn attacking enemy
  forces into ambush areas, and to retain areas from which to launch the striking force.
  6-189. A mobile defense requires assigned areas of considerable depth. Units shape the battlefield causing
  an enemy force to overextend its lines of communications, expose its flanks, and dissipate its combat power.
  Likewise, units must be able to move their forces into a position where they can defeat an attacking force.
  Divisions and larger formations normally execute mobile defenses. (See ADP 3-90 for more information on
  mobile defense.)
  RETROGRADE
  6-190. A retrograde is a type of defensive operation that involves organized movement away from the
  enemy (ADP 3-90). The three variations of the retrograde are delay, withdraw, and retirement. An enemy
  force may compel these operations, or units may execute them voluntarily, such as when a security force
  executes a rearward passage of lines through a main battle area. In either case, the higher echelon
  headquarters executing the retrograde must approve the operation before its initiation. A retrograde is not
  conducted in isolation; it is a transitional operation. It is part of a larger maneuver scheme designed to
  preserve combat power for future operations. Forward-stationed forces should be prepared to execute
  retrograde operations as part of a multinational force when outnumbered during the early part of a conflict.
  DEFENSIVE OPERATIONAL FRAMEWORK CONSIDERATIONS
  6-191. In the defense, commanders typically retain the deep and rear areas, but they divide the close area
  into two distinct portions: the security area and main battle area. Commanders use this approach to
  synchronize operations, including those in air, space and cyberspace, to defeat an enemy force throughout its
  depth. Figure 6-5 on page 6-36 depicts friendly defensive operations across a notional operational
  framework.