when was the department of defense founded
Creation. The Dept. of Defense was created by the National Security Act of 1947 by combining the Depts. of War and Navy and was called the National Military Establishment; it became the Dept. of Defense when the act was amended (1949).James V. Forrestal pioneered in this reorganization.he Secretary of the Army, the Secretary of the Navy, and the Secretary of the Air Forceâmade cabinet members by the act of 1947âwere subordinated (1949) to give the Secretary of Defense full cabinet authority over the department.