The Women's Army Corps (WAC) was the women's branch of the United States Army. It was created as an auxiliary unit, the Women's Army Auxiliary Corps (WAAC) on 15 May 1942, and converted to an active duty status in the Army of the United States as the WAC on 1 July 1943. Its first director was Colonel Oveta Culp Hobby. The WAC was disbanded in 20 October 1978, and all units were integrated with male units.

Auxiliaries are support personnel that assist the military or police but are organised differently from regular forces. Auxiliary may be military volunteers undertaking support functions or performing certain duties such as garrison troops, usually on a part-time basis. Unlike a military reserve force, an auxiliary force does not necessarily have the same degree of training or ranking structure as regular soldiers, and it may or may not be integrated into a fighting force. Some auxiliaries, however, are militias composed of former active duty military personnel and actually have better training and combat experience than their regular counterparts.