Lieutenant Colonel William R. Dunn, USAF (Retired) (1916–1995) was the first American ace of World War II. Joining the Canadian Army at the outbreak of war in September 1939, he was an infantryman until he transferred to the Royal Air Force (RAF) in late 1940. After service in an RAF Eagle Squadron, he joined the United States Army Air Forces in 1943. Transferring to the newly established U.S. Air Force in 1947, he also participated in the Chinese Civil War, Cold War and the Vietnam War.