Yanagi missions

The Yanagi missions (柳作戦, Yanagi sakusen; lit. 'Willow Missions'), or more formally the Submarine Missions to Germany (遣独潜水艦作戦, Kendoku sensuikan sakusen), 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.