The United States Navy

The Navy is administratively managed by the Department of the Navy, which is headed by the civilian Secretary of the Navy. The Department of the Navy is itself a division of the Department of Defense, which is headed by the Secretary of Defense. Traditionally, the highest ranking naval officer is the Chief of Naval Operations, a position currently held by Admiral Gary Roughead. However, currently the highest ranking naval officer is the Chairman of the Joint Chiefs of Staff, Admiral Michael Mullen.
Mission
The mission of the Navy is to maintain, train and equip combat-ready Naval forces capable of winning wars, deterring aggression and maintaining freedom of the seas.—Mission statement of the United States Navy