text: FM 7-100.1________________________________________________________________________________
  4-99. At each line, the contact force ideally forces the enemy to deploy his
  maneuver units and perhaps begin his artillery preparation for the attack.
  Then, before the contact force becomes decisively engaged, it maneuvers to its
  next preplanned line, behind the line occupied by the shielding force. While
  the original contact force is moving, the shielding force is able to keep the en-
  emy under continuous fires. When the original contact force passes to the
  rear of the original shielding force, the latter force becomes the new contact
  force. When the original contact force occupies its next line, it becomes the
  shielding force for the new contact force. In this manner, units continue to
  move by bounds to successive lines, preserving their own forces while delay-
  ing and destroying the enemy.
  4-100. Figures 4-1, 4-4, and 4-5, due to the operational scope of the overall
  maneuver defense shown, depict only the general location of a BTG or DTG
  as it moves to subsequent positions. These figures do not reflect the reality
  that the contact and shielding forces moving by bounds are likely to be de-
  tachments within a BTG or DTG. See FM 7-100.2 for examples of how this
  process works at the tactical level.
  4-101. Subsequent lines are far enough apart to permit defensive maneuver
  by friendly units. The distance should also preclude the enemy from engaging
  one line and then the other without displacing his indirect fire weapons. This
  means that the enemy, having seized one line, must change the majority of
  his firing positions and organized his attack all over again in order to get to
  the next line. However, the lines are close enough to allow the defending
  units to maintain coordinated, continuous fires on the enemy while moving
  from one to the other.
  4-102. OPFOR commanders may require a unit holding a line to continue
  defending, even if this means it becomes decisively engaged or enveloped.
  This may be necessary in order to allow the construction of defenses to the
  rear of the line this unit is defending.
  Disruption Force
  4-103. An operational-level defense may have an OSC occupying an opera-
  tional disruption zone if it is important to delay enemy forces to allow theater
  transition to adaptive operations. The task organization of such an OSC
  would have sufficient mobility to conduct a maneuver defense and a signifi-
  cant allocation of artillery and rocket units. The disruption force initiates the
  attack on the enemy’s combat system by targeting and destroying subsystems
  that are critical to the enemy. If successful, the disruption force can cause
  culmination of the enemy attack before the enemy enters the battle zone. In
  the worst case, the enemy would enter the battle zone unable to benefit from
  an integrated combat system and vulnerable to defeat by the main defense
  force.
  4-104. Forces committed to the disruption zone battle for an OSC usually
  would be a BTG or DTG, along with supporting and affiliated assets from the
  OSC. The OSC conducts the defense throughout the depth of the disruption
  zone. Maneuver units conduct the defense from successive battle positions.
  Intervals between these positions provide space for deployment of mobile
  attack forces, precision fire systems, and reserves.