The Japanese Navy was stripped of much of its war-making capability following the close of World War 2 (1939-1945) and, as such, languished without a capable submarine force for over a decade following the Japanese surrender to the Allies. Through the Military Assistance Program (MAP) from the United States, USS Mingo (SS-261), a Gato-class diesel-electric attack submarine from the war years, was loaned to the former American enemy after being decommissioned in January of 1947. She was then recommissioned in Japanese naval service as Kuroshio (SS-501) in August of that year to serve as an underwater training target for surface warships. Decommissioned in March of 1966, the hull was eventually sunk in 1973.
This exposure to a successful American submarine design prompted an internal movement for the remerging Japanese Navy to commission an all-new group of modern attack submarines. Initially three classes were part of the plan, each of a different displacement to suit particular undersea roles. In the event only one of the discussed classes ultimately emerged, this a 1,000 ton vessel which numbered just one in the class. The vessel saw its keel laid down on December 25th, 1957 and she was launched to sea on May 25th, 1959. The submarine was then officially commissioned as JDS Oyahsio (SS-511) on June 30th, 1960. She would serve actively for the next sixteen years.
As built, SS-511 displaced at 1,157 tons when surfaced and 1,445 tons when submerged. Her dimensions included a length of 258.5 feet, a beam of 23 feet and a draught of 15 feet. Propulsion came from a twin Kawasaki V9V22/30MATL diesel-electric engine arrangement developing 2,700 horsepower when surfaced and 5,960 horsepower when submerged. Maximum speed was 19 knots surfaced and 13 knots submerged with an operational range out to 10,000 nautical miles. Her crew complement numbered 65 and armament comprised of 4 x 533mm (21") torpedo tubes, all four fitted to the bow. Overall her design was conventional with a well-rounded bow and tapered stern holding the fin structure and propeller unit. Her sail was near midships. Besides the Japanese-led construction (handled by Kawasaki Heavy Industries of Kobe, Japan) which included elements borrowed from the wartime IJN I-201 series, Oyashio inherited some of the form and function garnered form operation of the earlier American submarine. This led to a capable undersea attack platform.
Oyashio, named after a Bering Straight current (the "Oyashio Current"), began her service with the new Japanese Maritime Self-Defense Force (JMSDF) on August 1st, 1962 as part of Submarine Squadron 1 (SUBRON 1) of the Kure District. She played guest during a visit to Pearl Harbor, Hawaii, site of the surprise naval attack against America which prompted the United States to enter into war with Japan. In early 1965, she was reassigned to SUBRON 2 and ended her days with Submarine Flotilla 1 into the mid-1970s.
JDS Oyashio was decommissioned on September 30th, 1976 after over a decade of faithful service to the rebuilding nation. Her hull was stripped of its usefulness and her hulk later scrapped. Her name was resurrected for IDS Oyashio (SS-590), a diesel-attack submarine appearing in 1998.