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 Air Force in the United Kingdom
The origins of the United States Air Force in the UK can be traced to a series of agreements made between 27 January and 27 March 1941 which provided for American naval, ground and air support for campaigns against Nazi Germany. As a result, a special U.S. Army Observer Group was activated in London on 19 May 1941. One of the first tasks of that unit was to reconnoitre areas regarded as potential sites for United States Army Air Forces (USAAF) installations.