Another battle that never happened... It was no secret that the IJN successfully operated spotter seaplanes from hanger-equipped submarines. But imagine the astonishment of the crew of the destroyer USS Bird on 27 August 1945 when they accepted the surrender of I-400, one of Japan's 2 operational submarine aircraft carriers (length 122m, displ. 6670 t submerged). When the surrender was announced, the I-400 and I401 were enroute from the home islands to attack the Allied naval base at Ulithi in the Caroline Islands with their total of six aircraft. I-401 surrendered shortly afterwards to the considerably smaller (95m, disp. 2391 t submerged) Balao-class submarine USS Segundo. The "Sen Toku" submarine program was a pet program of Admiral Yamamoto, but had dwindled in importance following his death in 1943. Incredible as it may seem, even as Okinawa was being overrun in early 1945, the two super-submarine's crews were still training singlemindedly in home waters with their equally-secret Aichi M6A "Seiran" submarine-launded bombers for a suicidal strike on the Panama canal- like the "Dambusters" of another time and place. Of course, the reality of the situation finally sank in, indicating that they might instead be more useful attacking the... "damn" enormous aircraft carrier parking lot at nearby Ulithi Atoll. These were the largest submarines ever built until the inception of nuclear-powered boats, and after an appropriate period of fact-finding, the Americans sank them rather than share their secrets with the Soviets. Modelled in Shade 10.5. Details from Wikipedia etc.