text: Security Operations
  13-119. The defensive covering force may be required to defend, delay, or counterattack. The covering force
  may have to reconnoiter and clear the area before establishing the cover if another unit is not currently
  occupying the covering force area. As in offensive operations, aerial reconnaissance is necessary to extend
  the covered area. Army aviation units can screen less threatened areas and rapidly reinforce with their fires
  when an enemy force heavily engages other elements of the covering force.
  13-120. Enemy forces may attempt to force the covering force back toward the MBA during the operation.
  If this happens, the covering force conducts a rearward passage of lines and a battle handover with the main
  body. Once the covering force completes its battle handover with the main body, they can do one of three
  things, separately or in combination. They can undergo reconstitution, execute economy of force missions,
  or become part of the echelon reserve. Alternatively, they may use them to locate and follow the movement
  of the enemy’s follow-on forces. They only establish BPs in the MBA as a last resort.
  13-121. The conduct of a rearward passage of lines is part of a defensive cover with its associated
  requirement to transfer responsibility for the battle between units. Units thoroughly plan this complex task
  as an integral part of the covering force mission. Covering force elements begin their rearward passage of
  lines either upon meeting disengagement criteria or upon order of the covering force commander. When any
  element of the covering force begins rearward movement to pass through the MBA, the higher commander
  must be informed. Passage of lines may not occur simultaneously for all covering force units. As some units
  begin passage, others may still be taking advantage of offensive opportunities in other parts of the security
  area. The covering force prepares to continue fighting in those portions of the security area where friendly
  subordinate forces are successful to set up offensive opportunities for the main body.
  13-122. The covering force exercises caution when issuing orders. Commanders at each echelon have a
  different perspective of the battle. This is never truer than in a covering force action. For example, while the
  covering force may be told to delay forward of a river line for 72 hours, the covering force commander may
  tell subordinate task force units to defend in certain BPs, perhaps for a specified period. Once the period
  expires, the covering force should not automatically retire from the covering force area. It must create enough
  resistance to force the enemy commander to deploy the enemy’s main forces. Commanders at each echelon
  precisely state the mission to their subordinate units without telling them how to do it. (See ADP 6-0 for
  doctrine on mission command.) Units, when told to delay, must fight the urge to shoot too little, pull back
  too early, and move back too far. It is imperative that commanders convey to subordinates precisely what
  their purpose is in the context of the overall mission.
  Rear Cover
  13-123. A rear cover mission is similar to a rear guard mission. A rear covering force protects the main body
  moving away from the enemy. The covering force deploys behind the forward maneuver units of the main
  body, conducts battle handover and passage of lines, and then defends or delays. Alternatively, the covering
  force may conduct a relief in place as part of a deception plan or to take advantage of the best defensive
  terrain.
  13-124. The covering force establishes passage points and assists the rearward passage of the main body.
  Following the passage of the main body, the mission is conducted the same as any other defensive cover
  operation. As the main body moves, the covering force displaces to subsequent phase lines in depth. If the
  enemy does not follow the withdrawing forces, contact may eventually be lost. Fighting a defense or delay
  is necessary if the enemy detects the movement and attacks.
  AREA SECURITY
  13-125. Area security is a type of security operation conducted to protect friendly forces, lines of
  communications, and activities within a specific area. Area security operations occur during all types of
  operations. The synchronization and integration of area and local security are essential to protecting the force.
  Area security operations support a higher echelon’s overall operation and require them to take advantage of
  local security measures performed by all units in the area, regardless of their command and control
  relationships. Although vital to the success of military operations, area security is normally an economy-of-
  force mission, often designed to ensure the continued conduct of sustainment operations that generate and
  maintain combat power.