The United States Department of Defense (DOD) is an executive department of the U.S. federal government charged with coordinating and supervising the six U.S. armed services: the Army, Navy, Marines, Air Force, Space Force, the Coast Guard for some purposes, and related functions and agencies. The Department of Defense is America's largest government agency. With their military tracing its roots back to pre-Revolutionary times, the department has grown and evolved with the nation. The DoD's mission is to provide the military forces needed to deter war and ensure the nation's security.