text: Security Operations
  13-22. Just like engagement criteria, it is critical for the commander to clearly state when the subordinate
  elements must break contact with enemy forces to prevent becoming decisively engaged and more
  importantly retain the ability to secure the identified protected objective. During security operations these
  criteria are often tied to planned transitions that are based on conditions for the security force to break contact
  with the enemy or the anticipated duration of the security operation.
  Security Force Size
  13-23. Main body commanders designate the size of the security force and its mission. This designation
  determines the limits of the security forces’ responsibilities. Table 13-1 shows typical sizes of security forces
  at various echelons in relation to their missions. The limited capabilities of most maneuver platoons prohibit
  them from having a mission separate from their parent company. Scout platoons are the exception to this
  rule.
  Table 13-1. Typical size of security forces for a given mission and echelon
  Security mission
  Echelon Flank or rear
  Screen Advance guard Cover
  guard
  Battalion task Scout platoon Company team
  force
  Brigade combat Company team or Battalion task Company team or Reinforced
  team (BCT) cavalry squadron force or reinforced cavalry squadron combined arms
  cavalry squadron battalion, battalion
  task force or
  reinforced cavalry
  squadron
  Division Cavalry squadron, Reinforced cavalry Reinforced cavalry Reinforced BCT
  combined arms squadron or BCT squadron,
  battalion, or combined arms
  battalion task force battalion, or
  battalion task force
  Corps Combat aviation Division, armored Division, armored Reinforced
  brigade, combined BCT, Stryker BCT BCT, Stryker BCT, division or
  arms battalion, combined arms armored BCT
  battalion task force battalion, battalion
  task force
  Echelons above Combat aviation Reinforced Combat aviation Reinforced
  corps (joint force brigade, armored division or corps brigade, armored division or corps
  land component or BCT, Stryker BCT BCT, or Stryker
  numbered Army) BCT
  LOCATION AND ORIENTATION OF THE SECURITY AREA
  13-24. Main body units determine the location, orientation, and depth of the security area where their
  security forces operate. Units identify avenues of approach and NAIs. Depth in the security area provides the
  main body with time to react to approaching enemy. Occupying a deep security area allows the security force
  to destroy enemy reconnaissance assets without compromising critical observation posts or positions. It also
  prevents enemy forces from penetrating the security area and prevents gaps from occurring when observation
  posts or units displace or are lost. Security forces cover less depth in a wide area because they have fewer
  resources to position in depth. Very shallow security areas may require units to resource their security forces
  to perform guard operations to provide more reaction time.
  13-25. Security force units conduct a detailed analysis of the terrain in the security area. They establish the
  initial dispositions of their security forces (usually a screen line) as far forward as possible on terrain that
  provides good observation of avenues of approach. Next, they assign clear responsibility for identified
  avenues of approach and designated NAIs. When conducting screen or guard operations, their initial screen
  lines are within supporting range of their main bodies yet provide the desired amount of early warning.