text: Chapter 6
  Figure 6-6. Relief in place
  PASSAGE OF LINES
  6-118. Passage of lines is an operation in which a force moves forward or rearward through another force's
  combat positions with the intention of moving into or out of contact with the enemy (JP 3-18). A passage
  may be designated as a forward or rearward passage of lines. A commander conducts a passage of lines to
  continue an attack or conduct a counterattack, retrograde, or security operation when one unit cannot bypass
  another unit's position. The conduct of a passage of lines potentially involves close combat. It involves
  transferring the responsibility for an AO between two commanders.
  6-119. Commanders must recognize that the transfer of control has impacts on FS. For example, the FS
  support attack/delivery system may have an on-order support relationship. Responsibility for FS coordination
  passes from the FSCOORD of one force to the FSCOORD of the other force at the time the force commanders
  change C2.
  6-120. Close coordination of plans between the commanders and staffs of the involved forces is mandatory.
  Once the passage of lines is ordered, the FSCOORD of the passing force in a forward passage of lines should
  send a liaison section to the FSCOORD of the force in contact. In a rearward passage, the FSCOORD of the
  stationary force should send a liaison section to the FSCOORD of the passing force. FSCOORDs define and
  assign mutually agreed upon FS responsibilities to facilitate the passing force. Information that the two
  FSCOORDs should share and areas that should be coordinated are shown below. The important point to
  remember is that each unit will be in the AO of another unit for a period of time and that detailed coordination
  is vital to ensure that each of the two units understands how the other operates. The units must do the
  following:
  * Exchange unit SOPS.
  * Exchange existing targets and fire plans.