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.
Militia
The Militia Act of 1903 divided what had been the militia into what it termed the "organized" militia, created from portions of the former state guards to become state National Guard units, and the "unorganized" militia consisting of all males from ages 17 to 45, with the exception of certain officials and others, which is codified in . Some states, such as Texas, California, and Ohio, created separate state defense forces for assistance in local emergencies. Congress later established a system of "dual enlistment" for the National Guard, so that anyone who enlisted in the National Guard also enlisted in the U.S. Army. When the U.S. Air Force was established as an independent service in 1947, the National Guard was further divided into the Army National Guard and the Air National Guard. Under this construct, the 1933 defense act's "dual enlistment" facet was further amended so that enlisted soldiers and commissioned officers in the Army National Guard were also enlisted or commissioned in the Reserve Component of the U.S. Army. Enlisted airmen and commissioned officers in the Air National Guard were also enlisted or commissioned in the Air Reserve Component (ARC) of the U.S. Air Force.