Detachment "A" (often shortened to "Det A") was a clandestine United States Army Special Forces unit based in West Berlin during the Cold War. Officially designated as the 39th Special Forces Detachment (Airborne), it operated from 1956 until its inactivation in 1984. Detachment A was tasked with operations behind enemy lines in the event of a conflict with the Soviet Bloc, including sabotage of key targets and organizing stay-behind resistance in East Germany. Its existence and activities remained highly classified throughout its service.