"In a theater of operations, all modes of transport-air, motor, rail, and water move cargo from the water's edge in the communications zone (COMMZ) through the crops and into the division areas. This manual describes the transportation doctrine and organizational structures required for Army water transport operations in a generic theater.[...] This manual is primarily for unit and vessel masters, key personnel, higher headquarters staffs, theater planners, and commander's operational allied units. It covers roles, missions, and concepts of employment for individual craft, entire units, and groups of units."
Field Manual No. 55-50; FM 55-50