what is the job of the marine corps
United States Marine Corps The United States Marine Corps (USMC), also referred to as the United States Marines, is a branch of the United States Armed Forces responsible for conducting amphibious operations[11] with the United States Navy. The U.S. Marine Corps is one of the four armed service branches in the U.S. Department of Defense (DoD) and one of the seven uniformed services of the United States.
United States Marine Corps rank insignia The Sergeant Major of the Marine Corps is a billet and with it carries a special rank insignia, conferred on the senior enlisted Marine of the entire Marine Corps, personally selected by the Commandant of the Marine Corps.[6] It and the Marine Gunner are the only billets which rate modified rank insignia in place of the traditional rank insignia.[citation needed]