Submarines of the Imperial Japanese Navy
Imperial Japanese Navy submarines originated with the purchase of five Holland type submarines from the United States in 1904. Japanese submarine forces progressively built up strength and expertise, becoming by the beginning of World War II one of the world's most varied and powerful submarine fleets.
History of submarines
The Germans were slower to recognize the importance of this new weapon. A submersible was initially ordered by the Imperial Russian Navy from the Kiel shipyard in 1904, but cancelled after the Russo-Japanese War ended. One example was modified and improved, then commissioned into the Imperial German Navy in 1906 as its first U-boat, "U-1". It had a double hull, was powered by a Körting kerosene engine and was armed with a single torpedo tube. The fifty percent larger "SM U-2" had two torpedo tubes. A diesel engine was not installed in a German navy boat until the class of 1912–13. At the start of World War I, Germany had 20 submarines of 13 classes in service with more under construction.