<P> The United States Air Force became a separate military service on 18 September 1947 with the implementation of the National Security Act of 1947 . The Act created the National Military Establishment , later renamed the United States Department of Defense , which was composed of four of the five branches , the Army , Marine Corps , Navy , and a newly created Air Force . Prior to 1947 , the responsibility for military aviation was divided between the Army for land - based operations and the Navy and Marine Corps for sea - based operations from aircraft carrier and amphibious aircraft . The Army created the first antecedent of the Air Force on 1 August 1907 , which through a succession of changes of organization , titles , and missions advanced toward eventual separation 40 years later . The predecessor organizations leading up to today 's U.S. Air Force are : </P>
<P> The United States Air Force became a separate military service on 18 September 1947 with the implementation of the National Security Act of 1947 . The Act created the National Military Establishment , later renamed the United States Department of Defense , which was composed of four of the five branches , the Army , Marine Corps , Navy , and a newly created Air Force . Prior to 1947 , the responsibility for military aviation was divided between the Army for land - based operations and the Navy and Marine Corps for sea - based operations from aircraft carrier and amphibious aircraft . The Army created the first antecedent of the Air Force on 1 August 1907 , which through a succession of changes of organization , titles , and missions advanced toward eventual separation 40 years later . The predecessor organizations leading up to today 's U.S. Air Force are : </P>
which of the u.s. military branches was originally a part of the u.s. army
which of the u.s. military branches was originally a part of the u.s. army
The United States Air Force
The United States Air Force