text: Chapter 3
  posts, tactical command posts or their equivalents, rear command posts, and mobile command groups. At the
  corps level and below, every echelon of command has a main command post and a tactical command post.
  Corps and divisions are also equipped with a rear command post, giving them the flexibility to delegate
  specific C2 responsibilities to nodes positioned to control deep, close, and rear areas.
  MAIN EFFORT, SUPPORTING EFFORT, AND RESERVE
  3-163. Commanders designate a subordinate unit as a main effort when its mission at a given point in time
  is most critical to overall mission success. Commanders weight the main effort with additional combat power.
  Typically, commanders shift the main effort one or more times during execution. When commanders
  designate a unit as the main effort, it receives priority of support and resources to maximize combat power.
  Commanders establish clear priorities of support, and they shift resources and priorities to the main effort as
  circumstances and the commander’s intent require. The unit that directly accomplishes the mission is usually
  the main effort when it conducts its mission. Commanders typically designate priority for sustainment to
  units that they anticipate to be the main effort. This helps maximize the combat power of a unit before it
  becomes the main effort. Shifting a priority of sustainment to the current main effort might be too late to be
  effective.
  3-164. A supporting effort is a designated subordinate unit with a mission that supports the success of the
  main effort (ADP 3-0). Commanders resource supporting efforts with the minimum assets necessary to
  accomplish the mission. Forces often realize success of the main effort through success of supporting efforts.
  A main effort in an earlier phase can be a supporting effort for a main effort in a later phase.
  3-165. A reserve is that portion of a body of troops that is withheld from action at the beginning of an
  engagement to be available for a decisive movement (ADP 3-90). A reserve is an uncommitted force, and it
  does not normally have a full suite of combat multipliers available to it until it is committed. It is the echelon’s
  main effort once it is committed. Commanders constitute a reserve and base the size of the reserve on the
  level of uncertainty in the current tactical situation. Commanders consider survivability, mobility, and the
  most likely mission when positioning their reserve. While commanders can assign their reserve a wide variety
  of tasks, through planning priorities, to perform on commitment, a reserve remains prepared to accomplish
  other missions. The primary purposes for a reserve are to—
  (cid:122) Exploit success.
  (cid:122) Counter tactical reverses that threaten the integrity of the friendly force’s operations.
  (cid:122) Retain the initiative.
  3-166. Once a reserve is committed, units reconstitute a new one whenever possible. When a commander
  assigns a unit the mission of being the reserve, the commander gives the unit a list of planning priorities.
  Typically a reserve has no more than three planning priorities because of the time it takes to adequately
  prepare for each priority.