text: Chapter 2
  Support Force
  2-39. The support force is responsible for fixing defending enemy forces along a broad front to allow the
  breach and assault forces to penetrate along a narrow front. The support force is a supporting effort to the
  breach and assault forces.
  Assault Force
  2-40. The assault force is responsible for seizing the penetration objectives on the far side of the penetration.
  It is typically the main effort. Depending on the situation the assault force may have a follow-and-support
  mission to the breach force.
  Reserve
  2-41. The use of the reserve avoids diverting the assault element from attacking the final objective of the
  penetration. Units assign subordinate units the tactical mission tasks of follow-and-support or follow-and-
  assume to ensure rapid exploitation of initial success.
  See paragraphs 2-51 through 2-57 for how these forces execute a penetration.
  Control Measures
  2-42. A unit conducting a penetration normally has a narrower assigned area than a unit conducting a frontal
  attack. The minimum control measures for a penetration are—
  * An assigned area to every maneuver unit.
  * Axis of advance or a direction of attack.
  * A line of departure (LD) or line of contact (LC).
  * The time of the attack or time of assault.
  * Phase lines.
  * An objective.
  * Limits of advance (LOAs) to control and synchronize attacks. (Units can use BHLs instead of
  LOAs if they know where they will likely commit their follow and assume forces.)
  * Checkpoints.
  * Graphic control measures associated with breaching operations, such as points of breach and lanes.
  * Probable lines of deployment.
  * Support by fire positions and attack by fire positions.
  * Fire support coordination measures.
  2-43. The lateral boundaries of a unit or units assigned the main effort are narrow to help maintain the mass
  necessary at the area of penetration. Units locate LOAs far enough beyond the enemy’s main defensive
  positions to complete their breach of those positions. They adjust existing boundaries to accommodate the
  new situation if operations result in opportunities to exploit success and pursue retreating enemy forces or
  expand the penetration.
  Planning a Penetration
  2-44. The success of a penetration depends primarily on a coordinated and synchronized plan executed at a
  high tempo against comparatively weak enemy defenses. The terrain behind an area selected to penetrate
  must allow follow-on forces to proceed from the breach to a deeper objective.
  2-45. The depth of an enemy position and the relative strength of attacking echelons determine the width of
  a penetration. The availability of artillery, air support, and other combat enablers for an attacking force helps
  units determine relative combat power. A wider gap allows friendly forces to pass through more quickly and
  in large-sized formations, making it more difficult for enemy forces to close the gap. The deeper a penetration,
  the easier it is to expose an enemy force’s flanks by the breach, and the less likely it is that an enemy force
  will be in a position to restore its front by falling back.