This may not be widely known but the Japanese are highly regarded in naval circles for their submarine technology. In World War II, the Imperial Japanese Navy fielded perhaps the most diverse range of submarines, from the midget for special operations to subs carrying bombers! In modern times, the Japanese Soryu class is seen as a very effective hunter-killer displacing 4,200 tonnes. It can voyage over 6000 nautical miles (11000+ km) and last 100 days in sea. But Japan does not export any as its pacifist constitution does not allow it. The result is lack of expertise in bidding for international submarine contracts. Apparently this deficiency has cost them potential contracts in India and Australia.