text: Defense
  Figure 7-8. Area defense, noncontiguous area of operations
  BATTLE POSITION
  7-100. Abattle positionis a defensive location oriented on a likely enemy avenue of approach (ADP 3-90).
  The BCT commander assigns a battle position to a battalion to control the battalion’s fires, maneuver, and
  positioning. Usually,the commander assigns boundaries to provide space for the battalion security,support,
  and sustainment elements that operate outside a battle position. When the commander does not establish unit
  boundaries,the BCT is responsible for fires,security,terrain management,and maneuver between positions
  of adjacent battalions. The battle position prescribes a primary direction of fire by the orientation of the
  position. The commander defines when and under what conditions the battalion can displace from the battle
  position or maneuver outside it. The use of prepared or planned battle positions,with the associated tasks of
  prepare or reconnoiter,provides flexibility to rapidly concentrate forces and adds depth to the defense.
  7-101. There are five types of battle positions: primary, alternate, supplementary, subsequent, and strong
  point. The commander always designates the primary battle position. The commander designates and
  prepares alternate,supplementary,and subsequent positions as required.
  7-102. Aprimary positionis the position that covers the enemy’s most likely avenue of approach into the
  area of operations (ADP 3-90). Always designate this position.Analternate positionis a defensive position
  that the commander assigns to a unit or weapon system for occupation when the primary position becomes
  untenable or unsuitable for carrying outthe assigned task (ADP 3-90). The alternate position covers the same
  area as the primary position. A supplementary positionis a defensive position located within a unit’s assigned
  area of operations that provides the best sectors of fire and defensive terrain along an avenue of approach