text: Chapter 9
  dramatically influencing the ratio of forces at these points of attack. Defending units quickly determine their
  enemy force’s intent and the effects of terrain. This allows defending units and their weapon systems to
  concentrate the effects of combat power against enemy forces at those points and restore a more favorable
  force ratio.
  9-91. Units carefully plan and coordinate the withdrawal of their forward security forces through MBA
  forward positions. MBA forces assume responsibility for a battle at the BHL. Units may find it necessary to
  increase the intensity of the direct and indirect fire support they provide to these forward security forces. This
  support allows those security forces to break direct contact with an enemy force as they approach the BHL
  and FEBA and conduct a rearward passage of lines. Units may also employ obscuration to assist in the
  retrograde maneuver of their security forces. Units guard rearward passage lanes in obstacle complexes left
  for the withdrawal of their security forces and arrange for closing those lanes after the passage of those forces.
  MBA forces provide other support as required to assist the withdrawal of these security forces.
  9-92. Attacking enemy forces try to find vulnerabilities and passage points after they reach the MBA,
  possibly by conducting a series of probing attacks. Defending units engage enemy lead forces as these attacks
  develop. Defending units select and reinforce terrain to canalize attacking enemy forces and limit the
  available maneuver space. This limited maneuver space tends to slow enemy advances and cause enemy
  formations to compress with resulting increased force densities. These conditions favor the employment of
  defensive fires and air support. Defending units employ simultaneous and sequential fires to impose the
  maximum possible enemy losses at this stage of a battle.
  9-93. Subordinate elements maneuver using massed direct and indirect fire and movement to gain positional
  advantage over assaulting enemy forces. Commanders also direct engineer obstacle and sustainment efforts
  by assigning priorities. They reposition forces to meet enemy forces where they actually are rather than where
  they projected enemy forces would be. Commanders direct operations and support subordinate elements by
  providing the necessary functional and multifunctional support and sustainment assets. They control the
  commitment of their reserves. Units engage enemy follow-on forces with long-range rockets and air support
  at division echelons and above. Units can defeat an echeloned enemy’s attack in detail, one echelon at a time,
  if they can delay the entry of enemy follow-on forces into the MBA. This is because disrupting the enemy
  force’s timetable can lead to the creation of exploitable gaps between the enemy force’s committed and
  subsequent echelons.
  9-94. Gaps between defensive positions may be necessary within the MBA due to a lack of defending forces.
  Units do not leave gaps in or near points where they project enemy forces will commit their main effort.
  Units continue to observe these gaps and cover them with their available fires. Where possible, units block
  these gaps by emplacing obstacles or moving in friendly forces.
  9-95. Commanders clearly define responsibilities for dealing with each enemy penetration. They take steps
  to block enemy MBA penetrations and destroy any penetrating enemy forces as soon as possible. This usually
  requires the employment of friendly reserves. Units may need to extend defensive actions within the depth
  of their assigned areas to counter enemy penetrations not stopped farther forward.
  9-96. Units do not allow attacking enemy forces to consolidate on any newly won objectives, unless this fits
  in their operational concepts for the defense. Generally, units conduct local counterattacks with available
  local resources to prevent enemy forces from consolidating on those objectives. The smallest possible units
  conduct these local counterattacks. However, commanders remain aware of the need to avoid piecemeal
  commitment. Units do not abandon their positions unless this action aligns with their higher echelon
  commander’s intent or that higher echelon commander grants them permission to do so. Defending forces
  contain enemy penetrations if they are unable to repulse enemy forces until they can act in concert with major
  counterattacking forces. Units orchestrate their counterattacks with the effects of all their elements of combat
  power, such as their supporting fire support systems.
  9-97. Units employ all available resources necessary to ensure success when counterattacking. Their
  reserves’ counterattack usually becomes their main effort on their commitment. One of commanders’ most
  critical decisions is the commitment of their reserve. Therefore, commanders avoid premature or piecemeal
  commitment of reserves. Commanders may reinforce their reserves before commitment to give them greater
  capabilities to counter enemy action. Units do not counterattack as an automatic reaction to an enemy
  penetration. Nor do commanders commit reserves solely because enemy forces reach a certain phase line or