While often associated with the Vietnam War, the helicopter made its combat debut in WWII. The Sikorsky R-4 was the first mass-produced helicopter and was used by the U.S. Army Air Forces for rescue missions in the jungles of Burma and the mountains of China. The first combat rescue occurred in April 1944, when Second Lieutenant Carter Harman flew an R-4 to rescue a downed pilot and three wounded British soldiers from behind enemy lines. This proved the utility of vertical-lift aircraft for medical evacuation (MEDEVAC), a role that would become central to military operations in the decades to follow.