text: Retrograde
  Terminating a Withdrawal
  11-93. Once the withdrawing force successfully disengages from the enemy force, it has two options. It can
  rejoin the overall defense under conditions that are more favorable, or it can transition into a retirement and
  continue to move away from the enemy force and toward its next mission.
  RETIREMENT
  11-94. A retirement is when a force out of contact moves away from the enemy (ADP 3-90). A retiring unit
  organizes for combat, but it does not anticipate interference from enemy ground forces. Retirement operations
  are usually conducted to reposition forces for future operations or to accommodate the current concept of
  operations. Typically, another unit’s security force covers the movement of one formation as the unit
  conducts a retirement. However, enemy mobile forces, unconventional forces, air strikes, air assault
  operations, or long-range fires may attempt to interdict the retiring unit. Commanders plan for enemy actions
  and organize their forces to fight in self-defense.
  11-95. When a withdrawal from action precedes a retirement, the actual retirement begins after the unit
  breaks contact and organizes into its march formation organization. (While a force withdrawing without
  enemy pressure can also use march columns, the difference between the two situations is the probability of
  enemy interference.) Units conduct retirements as tactical road marches where security and speed are the
  most important considerations.
  11-96. Each retiring unit generally moves toward an assembly area, which should support the preparations
  for the unit’s next mission. Commanders consider unit capabilities to support defensive actions, if combat
  occurs during the retirement, when determining routes to assembly areas.
  11-97. The initial action in a retirement is to move sustainment units and supplies to the rear. At the
  designated time, the retiring unit executes a withdrawal from action and forms into a march formation. The
  unit can first move into an assembly area, if this step is necessary, before moving into a march formation to
  reestablish command and control or resupply. Once it forms a march formation, the force is prepared to
  initiate the retirement. During the initial phase, the force retires in multiple small columns. As the distance
  from the enemy force increases, smaller columns can consolidate into larger ones for ease of movement
  control. The number of routes and the potential for enemy contact influence how and when this occurs.
  Organization of Forces for a Retirement
  11-98. Commanders normally designate security elements and a main body in a retirement. Figure 11-7 on
  page 11-18 illustrates this organization of forces. The formations employed during a retirement depend on
  the number of available routes and the potential for enemy interference. Commanders typically move major
  elements to the rear simultaneously. However, limited roles or a flank threat may require echeloning of the
  movement in terms of time and ground locations.
  11-99. The terrain and the enemy threat dictate whether a retiring force establishes a single rear security
  force, which is usually a rear guard, or whether each column forms a separate rear security force. These
  security forces protect the rearward moving columns from surprise, harassment, and attack by any pursuing
  enemy force. Their size and composition depend on the strength and imminence of the enemy threat. These
  security elements generally remain in march columns unless potential exists for enemy interference. If an
  enemy force establishes contact, the rear security element conducts a delay.
  11-100. The retiring march columns normally require an advance guard augmented by engineers focused on
  mobility. Commanders focus their engineers supporting their rear guards on countermobility. They assign
  flank security elements to prevent potential enemy interference with their retiring force’s extended columns.
  Commanders may designate flank security responsibilities to subordinate march units.
  11-101. The main body organizes in a manner opposite that of an approach march. The movement of
  functional and multifunctional support and sustainment units ideally precedes the movement of combat
  forces. When necessary, elements of the main body can reinforce the rear guard or any other security element.
  Because fire support elements and attack aviation elements of the main body can respond rapidly, they are
  usually the first elements tasked for this mission.