The United States Marine Corps (USMC), also referred to as the United States Marines, is the maritime land force service branch of the United States Armed Forces responsible for conducting expeditionary and amphibious operations through combined arms, implementing its own infantry, artillery, aerial, and special operations forces. The U.S. Marine Corps is one of the eight uniformed services of the United States.
The Marine Corps has been part of the U.S. Department of the Navy since 30 June 1834 with its sister service, the United States Navy. The USMC operates installations on land and aboard sea-going amphibious warfare ships around the world. Additionally, several of the Marines' tactical aviation squadrons, primarily Marine Fighter Attack squadrons, are also embedded in Navy carrier air wings and operate from the aircraft carriers.
The history of the Marine Corps began when two battalions of Continental Marines were formed on 10 November 1775 in Philadelphia as a service branch of infantry troops capable of fighting both at sea and on shore. In the Pacific theater of World War II, the Corps took the lead in a massive campaign of amphibious warfare, advancing from island to island. As of 2022, the USMC has around 177,200 active duty members and some 32,400 personnel in reserve.
As outlined in and as originally introduced under the National Security Act of 1947, three primary areas of responsibility for the U.S. Marine Corps are:
Seizure or defense of advanced naval bases and other land operations to support naval campaigns;
Development of tactics, technique, and equipment used by amphibious landing forces in coordination with the Army and Air Force; and
Such other duties as the President or Department of Defense may direct.
This last clause derives from similar language in the Congressional acts "For the Better Organization of the Marine Corps" of 1834, and "Establishing and Organizing a Marine Corps" of 1798. In 1951, the House of Representatives' Armed Services Committee called the clause "one of the most important statutory – and traditional – functions of the Marine Corps".