INDIAN OCEAN (Nov. 9, 2020) The Arleigh Burke-class guided-missile destroyer USS John S. McCain (DDG 56) fires its mark-38 25mm gun during a pre-aim calibration live-fire gunnery exercise. 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)