The United States Navy (USN) is the naval warfare service branch of the United States Armed Forces and one of the seven uniformed services of the United States. It is larger than the next 13 largest navies combined in terms of battle fleet tonnage, according to one estimate. The U.S. Navy also has the world's largest carrier fleet, with 10 in service, one under construction (two planned), and two in reserve. The service has 317,054 personnel on active duty and 109,671 in the Navy Reserve. It operates 285 ships in active service and more than 3,700 aircraft.
The navy traces its origins to the Continental Navy, which was established during the American Revolutionary War and was essentially disbanded as a separate entity shortly thereafter. It played a major role in the American Civil War by blockading the Confederacy and seizing control of its rivers. It played the central role in the World War II defeat of Japan.
The 21st century United States Navy maintains a sizable global presence, deploying in such areas as East Asia, the Mediterranean, and the Middle East. It is a blue-water navy with the ability to project force onto the littoral regions of the world, engage in forward areas during peacetime, and rapidly respond to regional crises, making it an active player in U.S. foreign and defense policy.
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. The Chief of Naval Operations is a four-star admiral and the senior naval officer of the Department of the Navy. The Chief of Naval Operations is the most senior naval officer in the Department of the Navy. However, the CNO may not be the highest ranking naval officer in the armed forces if the Chairman or the Vice Chairman of the Joint Chiefs of Staff are Navy officers, who by law, outrank the CNO.