text: Chapter 13
  bounds, alternate bounds, or continuous marching. If the main body stops, the flank guard occupies blocking
  positions. As the speed of the main body changes, the flank guard changes its movement methods, which
  could result in the ability of the guard force’s capability to fight to gain time for the main body. If the main
  body continues to increase its rate of march, the guard force will either need to have additional resources
  attached to maintain tempo or the main body assumes more risk by screening a portion of the flank. The
  guard commander must not allow the force to fall behind the main body or stay stationary along the route
  becoming a lucrative target.
  13-96. If the flank guard becomes overextended, the guard commander informs the main body commander
  and recommends one of the following COAs:
  * Reinforce the flank guard.
  * Reduce the size of the flank guard’s assigned area.
  * Screen a portion of the area and guard the rest.
  Rear Guard
  13-97. The rear guard protects the exposed rear of the main body. This occurs during offensive operations
  when the main body breaks contact with flanking forces or during a retrograde. Units may deploy a rear guard
  behind both moving and stationary main bodies. The rear guard for a moving force displaces to successive
  BPs along PLs or delay lines in depth as the main body moves. The nature of enemy contact determines the
  exact movement method or combination of methods used in the displacement (successive bounds, alternate
  bounds, and continuous marching).
  13-98. During a retrograde, the rear guard normally deploys its ground maneuver elements abreast, behind
  the main body’s forward maneuver units, generally across the entire assigned area. After the main body
  conducts a rearward passage of lines, the rear guard accepts battle handover and then defends or delays.
  Alternatively, the rear guard may conduct a relief in place as part of a military deception plan or may take
  advantage of defendable terrain. In both cases, the rear guard establishes passage points and assists the
  rearward passage of the main body, if necessary. The rear guard accomplishes its defensive mission in the
  same way as any other guard operation after the main body clears the security area. As the main body moves,
  the rear guard moves to subsequent PLs in depth. Contact with the enemy force may eventually be lost if it
  does not follow the retrograding friendly force. Fighting a defense or a delay is necessary if an enemy force
  detects the movement and attacks.
  COVER
  13-99. Cover is a type of security operation done independent of the main body to protect them by fighting
  to gain time while preventing enemy ground observation of and direct fire against the main body (ADP 3-
  90). The covering force’s distance forward of the main body depends on the main body commander’s
  intentions and instructions, the terrain, the enemy location and strength, and the main body and covering
  force’s rates of march. The frontage assigned to a security force executing a cover is the same frontage as the
  assigned area of the main body. It is here that the covering force executes assigned tasks. The biggest
  difference between a guard force and a covering force is that a covering force is able to operate independently
  of the main body, while a guard force relies on indirect support from the main body.
  13-100. A covering force, or portions of it, often become decisively engaged with enemy forces. Therefore,
  the covering force must have substantial combat power to engage the enemy and accomplish its mission. A
  covering force develops the situation earlier than a screen or a guard force. It engages longer and more often
  and defeats larger enemy forces.
  13-101. While a covering force provides more security than a screen or guard force, it also requires more
  resources. Before assigning a cover mission, the main body commander determines if the unit has enough
  combat power to resource a covering force and the main effort. When the commander lacks the resources to
  support both, the main body commander must assign the security force a less resource intensive security
  mission, either a screen or a guard.
  13-102. A covering force performs all the tasks of screening and guard forces. A covering force for a
  stationary force performs a defensive mission, while a covering force for a moving force generally conducts