United States Air Force
The U.S. War Department created the first antecedent of the U.S. Air Force, as a part of the U.S. Army, on 1 August 1907, which through a succession of changes of organization, titles, and missions advanced toward eventual independence 40 years later. In World War II, almost 68,000 U.S. airmen died helping to win the war, with only the infantry suffering more casualties. In practice, the U.S. Army Air Forces (USAAF) was virtually independent of the Army during World War II, and in virtually all ways functioned as an independent service branch, but airmen still pressed for formal independence. The National Security Act of 1947 was signed on 26 July 1947 by President Harry S Truman, which established the Department of the Air Force, but it was not until 18 September 1947, when the first secretary of the Air Force, W. Stuart Symington, was sworn into office that the Air Force was officially formed as an independent service branch.
United States Army Air Forces
The AAF administered all parts of military aviation formerly distributed among the Air Corps, General Headquarters Air Force, and the ground forces' corps area commanders, and thus became the first air organization of the U.S. Army to control its own installations and support personnel. The peak size of the AAF during the Second World War was over 2.4 million men and women in service and nearly 80,000 aircraft by 1944, and 783 domestic bases in December 1943. By "V-E Day", the Army Air Forces had 1.25 million men stationed overseas and operated from more than 1,600 airfields worldwide.