text: Chapter 9
  Area Defense
  This chapter addresses general considerations, organization of forces, and control
  measures typical to an area defense. It then discusses how to plan, prepare, and execute
  an area defense. Lastly, this chapter discusses the variations of the area defense.
  GENERAL CONSIDERATIONS FOR AN AREA DEFENSE
  9-1. An area defense capitalizes on the strength inherent in a closely integrated defensive operation. An
  area defense enables forces to consolidate, reorganize, and transition to another tactical operation, such as
  the offense. Commanders may assign their subordinate units the task of conducting an area defense.
  Subordinate echelons defend within their assigned areas as part of their higher echelon’s operations.
  9-2. Units conduct an area defense when—
  * Directed to defend or retain specified terrain.
  * They cannot resource a striking force.
  * Their available forces possess less mobility than enemy forces.
  * The terrain affords natural lines of resistance and limits the enemy force to a few well-defined
  avenues of approach, thereby restricting the enemy force’s maneuver.
  * They have enough time to organize their defensive positions.
  * Terrain constraints and lack of friendly air superiority limit the striking force’s options in a mobile
  defense to a few probable employment options.
  * Conditions require the preservation of forces when transitioning from a focus on the performance
  of offensive operations to stability tasks.
  9-3. Units conducting an area defense combine static and mobile tasks to accomplish their missions. Static
  actions usually consist of fires from prepared positions. Mobile actions include using the fires provided by
  units in prepared positions as a base for counterattacks and repositioning units between defensive positions.
  Units can use their reserves and uncommitted forces to conduct counterattacks and spoiling attacks to
  desynchronize enemy forces or prevent them from massing.
  ORGANIZATION OF FORCES FOR AN AREA DEFENSE
  9-4. An area defense is organized with a security force, main body, and a reserve. Since an area defense
  focuses on retaining key terrain, most of the unit’s combat power in the main battle area is positioned to
  support the defense of that terrain, while security forces provide early warning. See paragraphs 9-24 through
  9-37 for more information on position selection in the defense.
  SECURITY FORCE
  9-5. Units balance their need for strong security forces to shape their operation and their main body’s main
  effort. They usually allocate security forces to provide early warning and protect those main body forces,
  systems, and locations necessary to conduct their main effort from unexpected enemy contact. The location
  of these security forces is usually in front of the main defensive positions where forces are contiguous with
  one another. These security forces locate on avenues of approach between their respective protected forces
  and known or suspected enemy force locations on noncontiguous battlefields.