Combat service support
Combat service support (CSS) is the set of "essential capabilities, functions, activities, and tasks necessary to sustain all elements of operating forces in theater at all levels of war. Within the national and theater logistic systems, it includes but is not limited to that support rendered by service forces in ensuring the aspects of supply, maintenance, transportation, health services, and other services required by aviation and ground combat troops to permit those units to accomplish their missions in combat. Combat service support encompasses those activities at all levels of war that produce sustainment to all operating forces on the battlefield." 
As part of the restructuring of the United States Army, fewer pure combat service support units, of larger than battalion size, will exist. They are apt to be, instead, in Combat Support Brigades and Sustainment Brigades.
- US Department of Defense (12 July 2007), Joint Publication 1-02 Department of Defense Dictionary of Military and Associated Terms, JP 1-02
- As opposed to combat engineering