Submarines of the Imperial Japanese Navy
The ("I-15"-class) submarines (, , , , , , , , , , , , , , , , , , , ) were the most numerous type of submarines of the Imperial Japanese Navy during World War II. In total 20 were made, starting with "I-15", the class ship. These were fast, very long ranged, and carried a single Yokosuka E14Y seaplane, located in a hangar in front of the conning tower, launched by a catapult.
Monsun Gruppe
The German invasion of the Soviet Union in 1941 had ended the use of overland routes which were for the delivery of strategic materials from southeast Asia, and few Axis ships were able to avoid Allied patrols of the North Atlantic. Japan was interested in exchanging military technology with Germany, the Japanese submarine "I-30" initiated the submerged transport of strategic materials in mid-1942 by delivering 1500 kg of mica and 660 kg of shellac. Japanese submarines designed for the vast distances of the Pacific were more capable transports than the compact German U-boats which were designed for operations around coastal Europe; but large Italian submarines had proved ineffective for convoy attacks. The Italian Royal Navy ("Regia Marina") converted seven Italian submarines operating from BETASOM into "transport submarines" in order to exchange rare or irreplaceable trade goods with Japan. They were: The "Bagnolin", the "Barbarigo", the "Cappellini" (renamed "Aquilla III" in May 1943), the "Finzi", the "Giuliani", the "Tazzoli" and the "Torelli".