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 Corps
A major step toward creation of a separate air force occurred on 1 March 1935 with the activation of a centralized, air force-level command headed by an aviator answering directly to the Army Chief of Staff. Called the "General Headquarters Air Force", the organization had existed in Army planning since 1924 as a subordinate element of Army General Headquarters, which would be activated to control all Army units in case of war mobilization. In anticipation of military intervention Cuba in 1933, the headquarters had been created on 1 October but not staffed. The Drum Board of 1933 had first endorsed the concept, but as a means of reintegrating the Air Corps into control by the General Staff, in effect reining it in.