Impressed with the DHC4's STOL capabilities and potential, the US Army ordered five for evaluation as YAC-1s and went on to become the largest Caribou operator, taking delivery of 159. The AC-1 designation was changed in 1962 to CV-2, and then C-7 when the US Army's CV-2s were transferred to the US Air Force in 1967. US and Australian Caribou aircraft had extensive service during the Vietnam War. In addition, some US Caribou were captured by North Vietnamese forces and remained in service with that country through to the late 1970s. Other notable military operators included Canada, Malaysia, India, and Spain.