text: Area Defense
  for defensive preparations. In an area defense, units plan major counterattacks as a branch or sequel to the
  main defensive operation.
  9-39. A spoiling attack preempts or disrupts an enemy force’s ability to launch an attack, while a
  counterattack prevents an enemy force from exploiting successes. The forces conducting either variation of
  attack need to be capable to develop the situation, defend themselves, and force the enemy to react. This
  allows friendly forces to place the enemy’s attack plan at risk. See Chapter 5 for more information on spoiling
  attacks and counterattacks.
  PREPARATION CONSIDERATIONS FOR AN AREA DEFENSE
  9-40. When planning for an area defense, units focus their collection activities on confirming templated
  enemy courses of action, identifying favorable terrain for the defense, and answering the commander’s
  critical information requirements. Information obtained from those activities may or may not cause units to
  refine their plans. Defensive preparations allow time for any necessary additional coordination and
  synchronization among different headquarters. They also allow for the conduct of those supporting efforts
  that fall within their defensive capabilities and OPSEC guidelines. Defending units may have to commit
  substantial forces to security operations or conduct spoiling attacks if they know that enemy forces will attack
  before they finish their defensive preparations.
  9-41. Units normally establish an area defense after they complete the deployment process of force
  projection, complete their offensive actions, or are in assembly areas. Commanders issue warning orders
  stating the mission and identifying any special considerations. While subordinate units complete their current
  missions, unit staffs perform detailed planning. Staffs coordinate for the pre-positioning of ammunition and
  barrier material in secure areas near the unit’s projected defensive positions before starting the operation.
  9-42. Upon receiving initial mission orders, defending units establish a local security posture and occupy
  hide positions in sector before beginning defensive preparations. Security forces immediately assume their
  security mission and prepare positions simultaneously. Commanders conduct reconnaissance of their
  defensive areas and establish forward security areas before their units occupy their defensive positions. Units
  may pre-position supplies, such as ammunition and barrier materiel, once they can secure those positions and
  supplies. The mission variables are the deciding consideration in establishing priorities. Those priorities can
  include—
  * Establishing local security and deploying security forces.
  * Emplacing communications assets to support the unit’s primary, alternate, contingency, and
  emergency communications for each primary, supplemental, and alternative positions.
  * Establishing contact points with any adjacent units so that their commanders can coordinate and
  synchronize their defensive efforts.
  * Identifying engagement areas where commanders seek to engage and destroy enemy forces.
  * Emplacing obstacles and surveying indirect fire targets to support these obstacles.
  * Positioning key weapon systems to engage into engagement areas and cover obstacles.
  * Planning fire control measures, such as TRPs, trigger lines, and FPFs to support these engagement
  areas.
  * Positioning the reserve.
  * Designating and appropriately clearing fields of fire.
  * Preparing primary fighting positions based on the anticipated fighting conditions, such as the time
  of day and weather conditions.
  * Providing concealment and camouflage for fighting and survivability positions as they are
  constructed.
  * Positioning observers who can see both targets and trigger lines.
  * Positioning any available critical friendly zones over friendly positions by establishing sensor
  coverage and direct communications links between sensors and shooters.
  * Installing limited-visibility aids, such as thermal hot spots and chemical lights on TRPs.
  * Updating range cards and sector sketches as required.
  * Preparing alternate fighting positions.