The Department of Defense, commonly referred to as the DoD, is responsible for overseeing and maintaining all government organizations directly related to the safety of the United States. They govern all branches of the military to ensure protection for the country.
The DoD places the security of the United States as its top priority and provides the military force needed to maintain that goal. The Army, Navy and Marine Corps were individual entities until 1947 when these groups were consolidated into one department called the National Military Establishment. The organization changed its name to the Department of Defense in 1949. The Air Force, Coast Guard and Guard Reserve are also included as part of the DoD. The DoD infrastructure is much larger than those organizations, however. It also includes the Missile Defense Agency, the National Security Agency, the Defense Intelligence Agency and Homeland Security.
The DoD headquarters is the Pentagon, located in Washington, D.C. The organization has a huge task, which most Americans understand as protection from all enemies, domestic and foreign. The DoD understands that national security includes a global presence, and they have commands in many other countries and areas, including Canada, the Middle East, Africa, West Asia, South America, Europe, the Mediterranean and the Caribbean.