The current Department of Defense includes the Army, Navy, Marine Corps, Air Force, and Space Force, all of which have histories separate from the Department of War. The Department of War only looked after the Army, while a separate department was also created for the Navy. Former President Harry Truman and other military leaders viewed this division of departments as an obstacle, believing it hampered American operations during World War II. Truman argued that it was also a factor in the failure to prevent the bombing of Pearl Harbor in 1941. In 1947, the National Security Act was introduced, which placed the Army, Navy, and Air Force under one department and one cabinet secretary. At the time, it was called the National Military Establishment, but it was soon renamed the Department of War.
