Ise and Hyūga during Operation Kita, but was unable to attack. Though targets of opportunity were poor compared to where US submarines were operating the class performed reasonably well, sinking numerous merchant/cargo ships and smaller Japanese warships along with large numbers of coasters and small vessels. They proved better suited for Far Eastern operations than the smaller S class, having greater crew comfort and range. Postwar After the war, all surviving Group One and Two boats were scrapped and the remainder fitted with snorts. In the late 1940s and 1950s, most were streamlined for quiet and higher-speed underwater operation against Soviet submarines, in place of the anti-surface-ship role that they had been designed for. In January 1948, it was formally acknowledged that the main operational function of the British submarine fleet would now be to intercept Soviet submarines slipping out of their bases in Northern Russia to attack British and Allied merchant vessels. The following April, the Assistant Chief of Naval Staff, Rear-Admiral Geoffrey Oliver, circulated a paper in which he proposed that British submarines take a more offensive role by attacking Soviet submarines off the Northern Russian coast and mining the waters in the area. With the dramatically reduced surface fleet following the end of the Second World War, he commented that this was one of the few methods the Royal Navy had for "getting to the enemy on his home ground." Much of the work carried out on the submarines was underpinned by results of measurements made using , which had been modified in July 1945 – September 1946 to become an acoustic trials submarine, with external tubes and guns removed, the bridge faired, the hull streamlined and some internal torpedo tubes blanked over. Starting in 1948, eight newer all-welded boats underwent extensive "Super-T" conversion at Chatham Dockyard. The modifications included the removal of deck guns and the replacement of the conning tower with a "sail", a smooth-surfaced and far more symmetrical and streamlined tower. An extra battery was installed, and a new section of hull inserted to accommodate an extra pair of motors and switchgear. This varied between in the earlier conversions and in the later ones. These changes allowed an underwater speed of or more and increased the endurance to around 32 hours at . The first boats to undergo this modification were in November 1948 – March 1951, followed by in June 1949 – September