151207-N-GL720-001 BETHESDA, Maryland (Dec. 7, 2015) Vice Adm. Matthew Nathan, Navy surgeon general and chief, U.S. Navy Bureau of Medicine and Surgery receives Distinguished Service Medal (Gold Medal in lieu of Second Award) from Chief of Naval Operations (CNO) Adm. John Richardson during his retirement ceremony. Nathan retired after 31 years of service. (U.S. Navy photo by James Rosenfelder/Released)