The 'M' in USMC stands for MARINE, which is a branch of the United States Armed Forces. The Marines are responsible for providing power projection from the sea, using the mobility of the U.S. Navy to rapidly deliver combined-arms task forces. They are also responsible for conducting amphibious operations, as well as other duties such as security and counter-terrorism. The Marines have a long and proud history of service to the United States, and are one of the most respected branches of the military.