Defense Headquarters is a term used to refer to the headquarters of a military organization. The most well-known example of this is the Pentagon, which is the headquarters of the United States Department of Defense. The Pentagon is an eight-letter word and is the most iconic symbol of the American military. It is located in Arlington, Virginia and is the world's largest office building. It houses the offices of the Secretary of Defense, the Joint Chiefs of Staff, and the National Military Command Center.