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 Aviation Branch
While not part of the present Army Aviation Branch's heritage, United States military aviation began in 1907 with the Army’s acquisition of its first heavier-than-air aircraft, an airplane built to Army specifications by the Wright brothers. During World War I, the Air Service's aircraft strength grew from a few dozen to more than 11,000 planes, and the number of aviation personnel came to total more than 190,000. The Army Air Service was created in May 1918. After World War I, General William Mitchell and other Air Service leaders spoke out forcefully in favor of an independent air force. Since they envisioned aviation as a separate striking force, capable of independent operations, they opposed its remaining a supporting arm of the ground forces. Although Congress, as well as most Army leaders, rejected Mitchell's argument, the Air Service did become a separate combat arm, equal in status to the infantry, cavalry, and artillery. In 1926, the name of the air arm was changed to Army Air Corps, and then, in June 1941, the Air Corps and other Army air elements were merged to form the Army Air Forces, co-equal with the Army Ground Forces and the Army Service Forces.