Since the 1970s, Japan has maintained a fleet of at least 18 diesel-electric submarines. Now, in the face of growing Chinese naval power, this fleet is to be increased, to 21 or 24. China currently has about 60 submarines, none of them as effective as the Japanese boats, despite seven of them being nuclear. The Japanese crews are also better trained, but the Chinese are building better ships with more intensively trained crews. Two other Chinese neighbors, South Korea and Australia, are also increasing their submarine forces.
For the last three decades, Japan has replaced their subs after about 25 years, with newer designs based on experience with the previous classes. The new expansion will probably be accomplished by building more of the new Soryu class. There are two Soryu class boats in service and four under construction. These 2,900 ton boats have a crew of 65, six 533mm (21 inch) torpedo tubes and 30 torpedoes or Harpoon anti-ship missiles. There are also two 76mm tubes for launching acoustic countermeasures. Sonar and electronics are superior to the previous class. These boats also have AIP (Air Independent Propulsion) that enables them to remain submerged for a week or more at a time. Top surface speed is 24 kilometers an hour, top submerged speed is 37 kilometers an hour.
Currently Japan also has eleven 2,700 ton Oyashio class subs, built 1994-2008. With a crew of 70, they are armed with six 533mm (21 inch) torpedo tubes and 27 torpedoes or Harpoon anti-ship missiles. Their sonar equipment is superior to that of the Harushio class. Top surface speed is 24 kilometers an hour, top submerged speed is 37 kilometers an hour.
There are five Harushio class boats, plus two diverted to training duties. These 2,400 ton boats were built 1987-1997 and have crews of 65-70 sailors. They are armed with six 533mm (21 inch) torpedo tubes and 26 torpedoes or Harpoon anti-ship missiles. They have hull mounted and towed sonar. Top surface speed is 24 kilometers an hour, top submerged speed is 37 kilometers an hour.