What is the Department of Defense?

Created in 1949, the Department of Defense was an outgrowth of the National Security Act of 1947, which had "unified" the armed services. The debate in Congress leading up to the 1947 legislation had its origins in the experiences of World War II, which, despite the overall success, had revealed numerous problems in command and control and the allocation of resources. Aiming to avoid similar situations in the future, President Harry S. Truman recommended a War Department plan calling for a highly centralized and closely unified structure, including a separate air force, under a single secretary of defense. The primary function of the DOD is national defense.