The IJN I-400 Class submarine ended up being the maximum submarine in WW ? and also the largest in the world prior to the development of nuclear submarines in 1960s.I-400 had enough fuel to bypass our planet one and a half times and could carry 3 Aichi M 6A 1�Seiran� aircraft that could be assembled for journey within minutes. One among their missions, that was never finished, reportedly would be to utilize the aircraft to drop bacteriological bombs on U.S. urban centers. Even so the bacteriological bombs could not be ready with time .Later, a mission was to bomb the Panama Canal to cut the supply lines of Allied forces but canceled finally. The I-400 and I-401 had been captured at sea per week following the Japanese surrendered in 1945.