text: Chapter 4
  occupied positions with a combination of patrols, fires, and natural and man-made obstacles. Units
  aggressively reconnoiter between positions within the airhead and forward of the airhead line in the
  security. They increase emphasis on reconnaissance forward of the airhead line during limited visibility.
  The airhead configuration allows the commander to shift forces, reserves, and supporting fires quickly to
  reinforceother areasofthe airhead. Regardlessof the formofdefense chosen, the force preparespositions
  indepthwithinitscapabilities.
  4-80. Defenseduringwithdrawal.Should withdrawalfromtheinitialpositionsberequired,thefinalareato
  which the airborne force withdraws must contain adequate space for maneuver, for protecting critical
  installations,andforplannedairlandingorairevacuationoperations.
  4-81. Defense against armor. During the initial phases of an airborne operation, one of the main defenses
  against enemy armor is air support. Aircraft attack enemy armor targets as they appear, as far as possible
  fromtheobjectivearea,andcontinuetoattackandobservethemaslongastheythreatentheairborneforce.
  Strong points defending the airhead use existing obstacles such as ditches, thick foliage, and structures,
  plus reinforcing obstacles such as mine fields, tank traps, demolitions, and man-made obstacles. Units
  emplace AT weapons in depth along avenues of approach favorable for armor. They cover all dangerous
  avenues of approach with planned fires. Javelins, AT-4s and light anti-armor weapons of the rifle
  companies, the tube launched, optically tracked, wire guided weapons of the battalion weapons company,
  and the antitank weapons of division and corps aviation units give the airborne force a substantial amount
  of antitank firepower. Some of the antitank weapons, organic to battalions that are in holding areas not
  underarmoredattack,canbemovedtoreinforcethreatenedareas.
  4-82. Defense against airborne assault: All personnel must recognize that the enemy can conduct airborne
  assault operations and must defend against these attacks. Helicopters afford the enemy one of its best
  meansofrapidlymovingsignificantoperatingforcestotheairheadarea.
  4-83. Friendly forces must counterattack an enemy airhead immediately with available forces and fires to
  disrupt the enemy’s plan and force build up, and continue until the enemy airborne assault has been
  neutralized.
  4-84. Defense against guerrilla action and infiltration: The defense must include plans for countering
  enemy guerrilla attacks or infiltrated forces attacking the airhead area. The basic defense against these
  attacksisanextensive patrol and warningsystem, anall-round defense, and designated reserve unitsready
  to move quickly to destroy the enemy force. Units must be especially alert during limited visibility to
  preventtheenemyfrominfiltrating.Iftheenemycanbuildupforcesintheairhead interior, itcaninfluence
  operations.Unitsmustlocateanddestroytheenemythathasinfiltratedtheairhead.
  SECTION V – FOLLOW-ON OPERATIONS
  4-85. An airborne assault is as rapid in its execution as it is time-consuming in its preparation.
  Commanders must develop contingency plans for possible follow-on operations. These plans should be
  modifiedbased on the most current intelligence. Advanced planning can allow more rapid decisionmaking
  andtimelycommitmentofforces.
  4-86. The employment of ABNAF on the ground is similar to that of other Infantry ground forces. The
  entire range of these operations include movement to contact, attack, area defense, or retrograde.
  Additional operations may include raids, linkup, relief in place, passage of lines, withdrawal (either
  overlandor byair),exfiltration, andnoncombatant evacuation. (RefertoFM 3-21.20,FM 3-21.10, andFM
  3-21.8formoreinformation.)
  SECTION VI – SUPPORTING OPERATIONS
  4-87. Airborne forces can deploy from a continental United States base directly to the objective area. A
  more common method would be for the airborne unit to firstdeployto a remote marshalling base or to an
  intermediate staging base (ISB) before establishing a lodgment in the area of operation. In certain
  circumstances,theobjectivecanbebeyondtherangeofaircraftoperatingfrom a remotemarshallingbase