The Department of Defense provides the military forces needed to deter war and ensure our nation’s security. The Army, Marine Corps, Navy, Air Force, Space Force and Coast Guard are the armed forces of the United States. The Army National Guard and the Air National Guard are reserve components of their services and operate in part under state authority. 

The Department of Defense personnel are the backbone of America’s national security. They represent the diverse makeup of our nation and support not only those on active duty but also families, veterans, and retirees through education, training, and benefit programs.

 

Our Mission

The mission of the Department of Defense is to provide military forces necessary to protect the security of our country. The U.S. military defends the homeland, deters adversaries, and builds security around the world by projecting U.S. influence and working with allies and partners. In case deterrence fails, the U.S. military is prepared to fight and win decisively against any adversary.

 

Office of the Secretary of Defense

The U.S. Secretary of Defense oversees the Department of Defense and acts as the principal defense policy maker and adviser. The Office of the Secretary of Defense (OSD) is responsible for policy development, planning, resource management and program evaluation. OSD includes the offices of top civilian defense decision-makers with regard to personnel, weapons acquisition, research, intelligence and fiscal policy, as well as offices the Secretary establishes to assist in carrying out assigned responsibilities.