The , or more formally the , were a series of submarine voyages undertaken by the Imperial Japanese Navy (IJN) during the Second World War, to exchange technology, skills and materials with Japan's Axis partners, principally Nazi Germany. These voyages had to run the gauntlet of the Western Allies naval superiority in the Indian and Atlantic Oceans; of the five westbound voyages, three arrived safely, with two submarines sunk en route, while of the three successful vessels only one completed her return voyage, with two sunk before reaching home. The Yanagi missions were matched by several reciprocal voyages by German U-boats, though these were outside the Yanagi scheme, as were several blockade-running cargo voyages to and from the Far East. The Yanagi missions The Yanagi missions were: In April 1942 departed Kure, Japan with a cargo of mica and shellac, and plans of the Type 91 aerial torpedo; after missions in the Indian Ocean with other IJN submarines, she detached in June to proceed to Lorient, arriving there in August 1942. She departed France later that month carrying German military technology, including plans for and a complete set of a Würzburg radar, eight torpedoes and five torpedo data computers, anti-tank guns, diamonds, 20mm anti-aircraft guns, and fifty Enigma machines, and arrived at Singapore in October. However, she struck a British mine on leaving Singapore for the last stage to Japan. Some equipment was salvaged, but most was lost. In June 1943 departed Kure with plans of the IJN's Type 95 torpedo, a reconnaissance aircraft and submarine equipment, and collected a cargo of tin, rubber and quinine at Singapore. She also carried a spare crew of 48 men from Kure tasked with bringing back a German U-boat, U-1224, which the Kriegsmarine had transferred to the IJN for examination and reverse engineering. The I-8 rendezvoused with the German submarine U-161 from Lorient who transferred two German technicians who installed a radar detector. She arrived at Brest in August. I-8 departed France in October 1943 with a variety of German technology, including: bomb and anti-aircraft gunsights, marine chronometers, a Daimler-Benz torpedo boat engine, electric torpedoes, machine guns, and penicillin, arriving at Kure in December after a round-trip voyage of . In October 1943 departed Kure for Singapore. At Singapore, she picked up a cargo of tin, tungsten, rubber and opium. She departed Singapore on 11 November but was intercepted and sunk on 13