text: Tactical Control Measures
  Figure A-30. Example zone for 1-66 Armor
  DEFENSIVE OPERATIONS CONTROL MEASURES
  A-62. The commander controls the defense by using control measures to provide the flexibility needed to
  respond to changes in the situation and allow the defending commander to rapidly concentrate combat power
  at the decisive point. Defensive control measures within a commander’s assigned area include designating
  the security area, BHL, MBA with its associated FEBA, and the echelon support area. The commander can
  use battle positions and additional direct fire control and FSCMs in addition to those control measures
  discussed earlier in appendix A to further synchronize the employment of combat power. The commander
  designates disengagement lines to trigger the displacement of subordinate forces. These common defensive
  control measures are discussed in alphabetical order in paragraphs A-63 through A-79.
  Battle Positions
  A-63. A battle position is a defensive location oriented on a likely enemy avenue of approach (ADP 3-90).
  A battle position is generally only used during defensive operations. The battle position (BP) is a symbol that
  depicts the location and general orientation of most of the defending forces. A commander’s use of a battle
  position does not direct the position of the subordinate’s entire force within its bounds since it is not an
  assigned area. There are five kinds of BPs—primary, alternate, supplementary, subsequent, and strong point.
  When assigning BPs, the higher echelon always designates the primary BP. The subordinate unit designates
  and prepares alternate, supplementary, and subsequent positions as time and other resources permit and if the
  terrain or situation requires them. Figure A-31 on page A-20 depicts the five kinds of BPs.