22 minutes and was of inestimable value to the entire crew," wrote the submarine's commanding officer. "The training was excellent and the boost to morale tremendous." Thornback set sail for Midway Island after the shelling of Urakawa, and arrived at the atoll on 8 August. Seven days later, Japan—hemmed in by veritable armadas of Allied ships and planes which were able to roam almost at will and unchallenged off her coast and in her skies—surrendered. Post-war service Thornback soon returned to the United States, where she was decommissioned at New London on 6 April 1946 and was placed in the Atlantic Reserve Fleet. Subsequently, brought to the Portsmouth Naval Shipyard, she was converted and reactivated under the Greater Underwater Propulsive Power Program (GUPPY). On 2 October 1953, the submarine was recommissioned, Lieutenant Commander Thomas C. Jones, Jr., in command, and assigned to Submarine Squadron (SubRon) 4. Shaking down in her new configuration, the submarine performed a "first" for submarines on 6 November 1954, when she snorkeled in the Mississippi River at New Orleans, Louisiana, from the Industrial Canal to the foot of Canal Street. With SubRon 4, the ship was based at Key West, Florida, and visited ports in the Caribbean Sea before entering the Charleston Naval Shipyard in February 1956 for overhaul. Upon completion of this work, the submarine was deployed to the Mediterranean Sea for a tour with the Sixth Fleet before returning to Key West in March 1957. While with SubRon 4, Thornback participated in operations supporting the Operational Development Force, the Fleet Sonar School, and the Fleet Training Unit at Guantanamo Bay, Cuba. On 2 June 1958, Thornback departed the Caribbean, bound for Londonderry Port, Northern Ireland, and operations with the joint Royal Navy-Royal Air Force antisubmarine school. While thus engaged, the submarine damaged her port propeller at Londonderry Port and became the first American submarine to be docked at Faslane by the Royal Navy. Thornback returned to the Sixth Fleet and her second Mediterranean deployment which lasted from 2 July to 24 September 1958. For the remainder of the ship's active career, she was based out of Charleston, South Carolina, conducting deployments to the North Atlantic, the Mediterranean Sea, and to the Caribbean Sea and operating in a support capacity as newer submarine types joined the Fleet. Thornback received one battle star for her World War II service. TCG Uluçalireis (S 338) Placed in a