SOUTH CHINA SEA (Dec. 4, 2021) Sailors conduct tactical room-clearing in the pilot house during the Navy Security Force Sentry (NSFS) course aboard the Arleigh Burke-class guided-missile destroyer USS John S. McCain (DDG 56). McCain is assigned to Destroyer Squadron (DESRON) 15, the Navy’s largest forward-deployed DESRON and the U.S. 7th Fleet’s principal surface force. (U.S. Navy photo by Mass Communication Specialist 2nd Class Markus Castaneda)