text: Chapter 3
  responsibilities, prevent fratricide, facilitate C2, coordinate fires, control maneuver, and organize operations.
  To facilitate this integration and synchronization, commanders designate targeting priorities, effects, and
  timing within their assigned areas. There are three types of assigned areas that a land component or ARFOR
  commander uses:
  (cid:122) Area of operations.
  (cid:122) Zone.
  (cid:122) Sector.
  3-129. An area of operations is an operational area defined by a commander for the land or maritime force
  commander to accomplish their missions and protect their forces (JP 3-0). An area of operations is defined
  by its boundaries. Within their AO, units integrate assigned and supporting capabilities, synchronize
  warfighting functions, and generate combat power against enemy forces to accomplish the mission.
  Responsibilities for an AO include—
  (cid:122) Terrain management.
  (cid:122) Information collection, integration, and synchronization.
  (cid:122) Civil affairs operations.
  (cid:122) Movement control.
  (cid:122) Clearance of fires.
  (cid:122) Security.
  (cid:122) Personnel recovery.
  (cid:122) Airspace management.
  (cid:122) Minimum-essential stability operations tasks which are—
  (cid:131) Establish civil security.
  (cid:131) Provide immediate needs (access to food, water, shelter, and medical treatment).
  Commanders can add, remove, or adjust AO responsibilities based on the situation and mission variables.
  Note. A land AO by definition does not include a volume of airspace to control. Airspace control
  authorities delegate airspace control to Army commanders based on the situation. All commanders
  must be prepared to enable or coordinate airspace management. (See JP 3-52 and FM 3-52 for
  more information on airspace control.)
  3-130. A zone is an operational area assigned to a unit in the offense that only has rear and lateral
  boundaries. The non-bounded side of a zone is open towards enemy forces. A higher echelon headquarters
  uses fire support coordination and maneuver control measures such as a limit of advance and a coordinated
  fire line to synchronize its deep operations with those of a subordinate unit. Zones allow higher headquarters
  to adjust deep operations without having to change unit boundaries. This gives greater flexibility to the higher
  headquarters for controlling deep operations, allowing subordinate units to focus on close and rear operations.
  Units treat everything behind the forward line of troops as an AO with its associated responsibilities. Units
  can subdivide a zone into subordinate AOs, zones, or sectors.
  3-131. A sector is an operational area assigned to a unit in the defense that has rear and lateral
  boundaries and interlocking fires. The non-bounded side of a sector is open towards the enemy. A higher
  echelon headquarters uses fire support coordination and maneuver control measures such as battle positions
  and trigger lines to synchronize subordinate units. Higher headquarters are responsible to synchronize
  employment of combat power forward of the main battle and security areas or coordinated fire line. Higher
  headquarters use sectors to synchronize and coordinate subordinate force engagement areas and allow for
  mutually supporting fields of fire, which do not require deconfliction between adjacent units. Units treat
  everything behind the forward line of troops as an AO with its associated responsibilities. Units can subdivide
  a sector into subordinate areas of operations, zones, or sectors.
  3-132. While there are many other control measures that enable terrain management (for example, position
  areas for artillery or tactical assembly areas) only AOs, zones, and sectors are part of the assigned area model.
  Commanders and staffs use AOs when the operation requires a higher level of control. Zones are best for
  front line units conducting high tempo offensive operations characterized by direct fire contact with the