when did the war department change its name
United States Department of War The War Department existed from August 7, 1789[1] until September 18, 1947, when it split into Department of the Army and Department of the Air Force and joined the Department of the Navy as part of the new joint National Military Establishment (NME), renamed the United States Department of Defense in 1949.
Joint Chiefs of Staff After the 1986 reorganization of the military undertaken by the Goldwater-Nichols Act, the Joint Chiefs of Staff does not have operational command of U.S. military forces. Responsibility for conducting military operations goes from the President to the Secretary of Defense directly to the commanders of the Unified Combatant Commands and thus bypasses the Joint Chiefs of Staff completely.