Legal Definitions - Department of Defense

The Department of Defense is a part of the United States government that is responsible for coordinating and overseeing military affairs and agencies responsible for national security. It was established in 1947 as the National Military Establishment and was later renamed to the Department of Defense in 1949.

The Department of Defense is made up of several components, including the Army, Air Force, Navy, Marine Corps, and Joint Chiefs of Staff. The Secretary of Defense is the head of the Department and is responsible for answering to the President as Commander-in-Chief.

For example, if the United States were to go to war, the Department of Defense would be responsible for coordinating and overseeing military operations. The Army, Air Force, Navy, and Marine Corps would all work together under the direction of the Joint Chiefs of Staff to carry out the mission.