text: Reconnaissance and Security
  employs technical assets to ensure continuous and overlapping surveillance. The commander also employs
  terrain data base analytical support systems to ensure the integration of friendly reconnaissance and
  surveillance assets to provide the necessary coverage. (SeeFM 3-90-2 for additional information.)
  GUARD
  5-82. Guard is a type of security operation done to protect the main body by fighting to gain time while
  preventing enemy ground observation of and direct fire against the main body(ADP 3-90). Units performing
  a guard task cannot operate independently because they rely upon fires and functional and multifunctional
  supportassets of the main body. A guard force differs from a screen in that it routinely engages enemy forces
  with direct and indirect fires. A screening force primarily uses indirect fires or air support to destroy enemy
  reconnaissance elements and slow the movement of other enemy forces.
  5-83. The BCT commander assigns a guard mission when expecting contact or has an exposed flank that
  requires greater protection than a screen can provide. The three types of guard operations are advance,flank,
  and rear guard. The commander can assign a guard mission to protect either a stationary or a moving force.
  The guard force commander normally conducts the guard mission as an area defense, a delay, a zone
  reconnaissance,or a movement to contact mission in the security area to provide reaction time and maneuver
  space to the main body. A guard operates within the range of the main body’s fire support weapons,deploying
  over a narrower front than a comparable sized screening force to permit concentrating combat power. Guards
  are most effective when air assets are integrated. The commander’s intent and end state determinethe nature
  and extent of required augmentation. (SeeFM 3-90-2 for additional information.)
  COVER
  5-84. Coveris 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).
  Security forcesprotect the main body by fighting to gain time,observe and reportinformation,and prevent
  enemy ground observation of and direct fire against the main body. In Army doctrine,acovering forceis a
  self-containedforce capable of operating independently of the main body,unlike a screen or guard force to
  conduct the cover task (FM 3-90-2). A covering force performs all the tasks of screening and guard forces.
  5-85. Adivisioncovering forceis usually a reinforced BCT that performs reconnaissance or othersecurity
  missions. The covering force area is the area forward of the forward edge of the battle area out to the forward
  positions initially assigned to the covering force. It is here that the covering force executes assigned tasks
  (FM 3-90-2). The width of the covering force area is the same as the main body’s area of operations. An
  adequately reinforced combined arms battalion, ABCT or Stryker brigade combat team (SBCT) Cavalry
  squadron,or SBCT Infantry battalion may perform a covering force mission if the division area of operations
  is narrow enough. These reinforcements typically revert to their parent organizations on passage of the
  covering force. BCTs and battalions typically organize a guard force instead of a covering force because their
  resourcesare limited.
  5-86. A covering force’s distance forward of the main body depends on the main body commander’s
  intentions and instructions,reinforcements,the terrain,the enemy location and strength,and the main body
  and covering force’s rate of march. Covering forces often become decisively engaged with enemy forces and
  therefore,must have substantial combat power to engage the enemy and accomplish the mission. A covering
  force develops the situation earlier than a screen or a guard force,fights longer and more often and defeats
  larger enemy forces. (SeeFM 3-90-2 for additional information.)
  AREA SECURITY
  5-87. Area security is a type of security operation conducted to protect friendly forces, lines of
  communications, and activities within a specific area (ADP 3-90). Area security operations allow
  commanders to provide protection to critical assets without a significant diversion of combat power.
  Protected forces range from echelon headquarters through artillery and echelon reserves to the sustaining
  base. Protected installations can be part of the sustaining base or they can constitute part of the area’s critical
  infrastructure.