text: Relief in Place
  15-25. In a simultaneous relief, the incoming unit begins moving from its current location to assembly areas
  in the assigned area of the outgoing unit. Once the relief begins, all elements involved execute the relief as
  quickly as possible. Both units are vulnerable to enemy attack because of the concentration, movement, and
  intermingling of forces in a simultaneous relief. Any unnecessary delay during execution provides enemy
  forces additional time to acquire and engage the forces involved. All units in the assigned area start under the
  operational control of the outgoing going unit commander until the time or event established in the operation
  order when the responsibility and authorities change to the incoming unit commander. Usually, the trigger to
  change from the outgoing commander to the incoming commander is when the incoming commander has
  sufficient communications to control the operation and roughly two thirds of the personnel responsible or
  security active in the assigned area.
  15-26. As the first incoming element arrives from the assembly area to assume the position, it establishes a
  screen of the outgoing unit’s positions as the tactical situation permits. The remainder of the incoming unit
  moves forward to positions behind the outgoing unit. The incoming unit may use the outgoing unit’s alternate
  and supplementary defensive positions to take advantage of any previous defensive preparations. At the
  previously established time or event, passage of command takes place. At that point the commander of the
  incoming unit informs all units involved in the relief of the passage of command.
  15-27. The relieved unit continues to defend. The incoming unit’s advance parties coordinate procedures
  for the rearward passage of the outgoing unit. On order, the outgoing unit begins withdrawing through the
  incoming unit and moves to assembly areas. Crew-served weapons are usually the first elements relieved
  after exchanging range cards. The incoming unit replaces them on a one for one basis to the maximum extent
  possible to maintain the illusion of routine activity. The outgoing unit’s functional and multifunctional
  support and sustainment assets assist both the outgoing and incoming units during this period.
  15-28. A relief does not normally require artillery units to relieve weapon system for weapon system unless
  the terrain limits the number of firing positions available. Generally, the outgoing unit’s artillery and other
  fire support assets remain in place until all other outgoing elements displace and are available to reinforce
  the fires of the incoming unit in case the enemy tries to interfere. If the purpose of the relief is to continue
  the attack, the artillery of both forces generally remains in place to support the subsequent operation.
  15-29. Multiple routes that allow only one-way traffic can simplify the forward and rearward movement of
  both units. The incoming unit controls both units’ traffic management assets. Commanders use these assets
  to help control unit and convoy movement on LOCs throughout their assigned area.
  15-30. A relief in place may involve the relief of an allied or coalition multinational force. Units consider
  these additional points when such reliefs occur:
  * Dissimilar unit organizations may require special adjustments in assigned areas.
  * Control of fire support may require special liaison.
  * Language difficulties may require an increased use of guides and translators and require more time
  to execute.
  * Using outgoing unit communications requires special signal arrangements and additional
  operators.
  * Ammunition and equipment incompatibility may make exchanging assets more difficult.