The Largest Submarine in The World, Sentoku

During World War II, Japan built Sentoku the largest submarine in the world. This class of submarine, which was also named I-400, had hangar constructed on the upper main deck to accommodate three floatplane bombers, Aichi M6A Seiran. The submarine was reported to be 60% larger than the largest American submarine. The Imperial Japanese Navy (IJN) ordered the construction of the I-400 submarine class as their secret weapons to destroy major US cities and the Panama Canal - the main route for the US to logistically supply their troops fighting against the Japanese in the Pacific. The Japanese had suffered great loss during the marine battles in Guadalcanal, and Midway as well as land battles in the Netherlands New Guinea island. It had been planned that the launching of surprised attacks on the Panama Cannal and US big cities would stop the US from immediately supplying their troops in that region thus providing enough time for the Japanese to consolidate and strengthen their troops.

Unfortunately for the Japan, the I-400 submarines could not fulfil their mission because the US had bombed Hiroshima and Nagasaki with nuclear weapon forcing the Japanese government to surrender without any condition. Sentoku and her sisters submarines could carry aerial torpedoes, three 800 kg bombs and twelve 240 kg bombs to arm their Seiran aircrafts. The propulsion of this submarine was powered by four 3,000 hp engines with enough fuel to travel around the world 1.5 times.