text: Security Operations
  advantage of established links with higher echelon sensors and collection assets. Patrols reconnoiter areas
  that observation posts cannot observe. The force retains a small reserve, if possible. The screening force
  establishes observation posts in depth on high-speed avenues of approach if forces are available and the depth
  of the security area allows. Screening force units plan routes between their initial and subsequent screen lines
  to facilitate rapid occupation of these subsequent screen lines. They deploy their assets in depth in positions
  where those assets can react to contingencies that develop during the screen mission. They take advantage of
  surveillance, target acquisition, and night observation equipment and information provided by higher level
  systems to expand the area and quality of security provided.
  13-64. Established observation posts employ cover and concealment to remain undetected. They report the
  presence of enemy elements. Prompt, accurate reporting of enemy force locations is essential to keep enemy
  forces from overrunning friendly observation posts. Units can reposition observation posts to keep contact
  with enemy forces. Observation posts employ fire support channels to request and control indirect fires to
  engage detected enemy forces. This helps screening observation posts avoid detection and prevents enemy
  forces from penetrating the screen line. Observation posts may engage enemy reconnaissance assets with
  their direct fire systems if indirect fires cannot destroy those enemy reconnaissance assets. Observation posts
  also attempt to slow the movement of other enemy elements, primarily using indirect fires and close air
  support.
  13-65. Observation posts report and request to move to the next screen line as enemy pressure threatens
  their security. Commanders establish criteria based on certain enemy or friendly actions that allow their
  screening forces to displace to subsequent screen lines. These criteria allow subordinates to use their initiative
  when conducting operations. Screening forces emphasize rapid movement while maintaining contact with
  enemy forces when displacing from one screen line to another. This ensures the rapid closing of any gaps in
  observation that occurred during movement. Likewise, screening force command elements displace as
  required to maintain control and avoid enemy detection and destruction. Screening forces repeat this
  procedure as often as necessary.
  13-66. Screening force commanders decide when to move from one screen to another. However, main body
  commanders decide when the screening force can conduct either a reconnaissance handover with the next
  echelon of reconnaissance or a battle handover with the main body.
  Executing a Moving Screen
  13-67. A screening force maintains a moving screen along the flanks and rear of the protected force, never
  to the front of a moving formation. A screening force is not employed in front of a moving formation because
  a screen does not prevent enemy forces from penetrating it and making contact with the protected force. Zone
  reconnaissance, reconnaissance in force, and guard are missions given to units in front of a moving force.
  The screen movement is keyed to time and distance factors associated with the main body’s movement. (See
  figure 13-6 on page 13-16.) Responsibilities for a moving flank screen begin at the front of the main body’s
  lead combat element and end at the rear of the protected force. They do not include front and rear security
  forces. A force executes a moving screen in the same way it conducts a stationary screen, except for the
  movement techniques.
  13-68. The lead element of a moving screen performs three tasks. It maintains contact with the protected
  force’s main body, reconnoiters the area between the main body and the security force’s routes of advance,
  and reconnoiters the security force’s route. It performs these tasks by conducting a zone reconnaissance.