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
The U.S. Army Air Service had a brief but turbulent history. Created during World War I by executive order of 28th President Woodrow Wilson after American entrance in April 1917 as the increasing use of airplanes and the military uses of aviation were readily apparent as the war continued to its climax, the U.S. Army Air Service gained permanent legislative authority in 1920 as a combatant arm of the line of the United States Army. There followed a six-year struggle between adherents of airpower and the supporters of the traditional military services about the value of an independent Air Force, intensified by struggles for funds caused by skimpy budgets, as much an impetus for independence as any other factor.