text: Chapter 5
  COAand to assist the protected force in countering it. Terrain information focuses on its possible use by the
  enemy or the friendly force, either for offense or for defense. Civil consideration is a key focus for
  information during the elements (offense,defense,and stability) of decisive action. Stationary security forces
  use combinations of observation posts,aviation,patrols,intelligence collection assets,and battle positions to
  perform reconnaissance. Moving security forces perform zone,area,or route reconnaissance along with using
  observation postsand battle positions to detect enemy movements and preparations.
  MAINTAIN ENEMY CONTACT
  5-76. Once the security force makes enemy contact, it does not break contact unless the main force
  commander specifically directs it. However, the individual security asset that first makes contact does not
  have to maintain that contact,if the entire security force maintains contact with the enemy. The security force
  commander ensures that subordinate security assets hand off contact with the enemy from one security asset
  to another in this case. The security force must continuously collect information on the enemy’s activities to
  assist the main body in determining potential and actual enemy COAs and to prevent the enemy from
  surprising the protected force. Depth in space and time enables security forces to maintain continuous visual
  contact,to use direct and indirect fires,and to maneuver freely.
  TYPES OF SECURITY OPERATIONS
  5-77. Security operations provide the protected force with varying levels of protection and are dependent
  upon the size of the unit conducting the security operation. All security operations provide protection and
  early warning to the protected force. Security operations encompass four types: screen, guard, cover, and
  area security.
  5-78. Security operations conducted in the security area—that area occupied by a unit’s security elements
  and includes the areas of influence of those security elements (ADP 3-90)—by one force or a subordinate
  element of a force that provides security for the larger force are screen,guard,and cover. The screen,guard,
  and cover security operations,respectively,contain increasing levels of combat power and provide the main
  body with increasing levels of security. The more combat power in the security force means less combat
  power for the main body. Normally,the BCT commander designates a security area in which security forces
  provide the BCT with reaction time and maneuver space to preserve freedom of action. (SeeFM 3-90-2 for
  additional information.)
  SCREEN
  5-79. Screenis a type of security operationthat primarily provides early warning to the protected force (ADP
  3-90). The screen provides the least protection of any security mission;it does not have the combat power to
  develop the situation. A screen is appropriate to cover gaps between forces, exposed flanks, or the rear of
  stationary and moving forces. The commander can place a screen in front of a stationary formation when the
  likelihood of enemy action is small,the expected enemy force is small,or the main body needs only limited
  time,once it is warned,to react effectively. If a significant enemy force is expected or a significant amount
  of time and space is needed to provide the required degree of protection,the commander assigns and resources
  a guard mission instead of a screen.
  5-80. A screening force observes,identifies,and reports enemy actions. The unit performing a screen may
  engage, repel, or destroy an enemy’s reconnaissance and surveillance element within its capabilities,
  augmented by indirect fires, Army aviation attacks, or close air support, but otherwise fights only in
  self-defense. The screen has the minimum combat power necessary to provide the desired early warning,
  which allows the commander to retain the bulk of the main body’s combat power for commitment at the
  decisive place and time. The depth of the screen is critical to allow reconnaissance handover of threat contact
  from one element to another without displacement from established observation posts. Screening forces use
  depth to delay,impede,and harass the enemy with indirect fires or air support to cause the enemy to deploy
  early and to prevent the enemy from identifying,penetrating,and exploiting the screen.
  5-81. Within an assigned area of operations, a security force normally conducts a screen by establishing a
  series of observation posts and patrols to ensure adequate observation of designate NAIs and TAI. The
  commander uses reconnaissance patrols (mounted,dismounted,and aerial),relocates observation posts,and