The concept of the door gunner originated during the Vietnam War, when helicopters were first used in combat in large numbers. The original personnel who served as early door gunners aboard CH-21, UH-34, and UH-1 helicopters in Vietnam, were enlisted men, with a designated and specially trained crew chief serving as both the aircraft's maintenance manager and a door gunner.
The concept of a door gunner developed during the Vietnam War when helicopters became frequently used in combat. The initial door gunners on CH-21, UH-34, and UH-1 helicopters were enlisted men who also served as the aircraft's maintenance manager and had specialized training for this position.