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.
Aviation Section, U.S. Signal Corps
In August 1914, soon after the passage of the act creating the Aviation Section, World War I began. The European powers showed an immediate interest in promoting military aviation but the Army's General Staff remained apathetic regarding development of aerial capabilities, as Captain Beck had charged the year before. The Chief Signal Officer continued restrictions on development and acquisition of aircraft that were perceived by the young aviators as detrimental to flying safety and likely to prevent the Aviation Section from providing aviation support to the Army comparable to that of the European powers in the event that the United States was drawn into the war. Officers who had testified against separation of aviation from the Signal Corps in August 1913 now were for it, marking the beginning of the movement that ultimately culminated in the creation of the United States Air Force 33 years later. Considerable friction developed between the young pilots from the line of the Army and their non-flying superiors in the Signal Corps, primarily over safety concerns the pilots felt were being disregarded in the interest of efficiency. (see Appropriations, growth, and "incipient mutiny" under Aeronautical Division, U.S. Signal Corps.)