In August 1939, the Secretary of War relocated his offices from the overcrowded State-War-Navy Building (Old Executive Office Building) to the Munitions Building. The Department of War headquarters remained in the Munitions Building, through the early years of World War II, until 1942, when some space became available in the Pentagon, which was under construction. The Munitions Building was turned over to the Navy in 1943, when the Department of War completely vacated the Munitions Building once construction of the Pentagon was completed.