Sgt. William Loughran encourages recruits from Kilo Company, 3rd Recruit Training Battalion, to give 100 percent during physical training at Marine Corps Recruit Depot Parris Island, S.C., Sept. 18, 2013. About 600 Marine Corps drill instructors train about 20,000 recruits who come to Parris Island annually. US Marine Corps photo by Cpl. Caitlin Brink/Released.