Soryu class is a new style submarine which is the first AIP (Air-Independent Propulsion) submarine in the Japan Maritime Self Defense Force. AIP allows a submarine to operate without the need to surface or use a snorkel to access atmospheric oxygen. It is said that Soryu is an evolved form of the Oyashio class submarine. The Oyashio is a class of Japanese diesel-electric submarine operated by the JMSDF. The submarines are larger than the earlier Harushio class submarines. Soryu`s submerged displacement,4.200t, is the world's largest class as a conventionally-powered submarine. The Soryu is equipped with the AC generator and the un-penetrating type periscope. Speed of Soryu is 13 knots surfaced and 20 knots submerged .