The Yanagi missions were a series of submarine voyages undertaken by the Imperial Japanese Navy 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 Alliesnaval 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, torpedoes and torpedo data computers, and 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 tasked with bringing back a German U-boat, U-1224, which the Kriegsmarine had transferred to the IJN for examination and reverse engineering. She arrived at Brest in August. I-8 departed France in October 1943 with a variety of German technology, 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 November in the Straits of Malacca by the British submarine HMS Taurus.
In November 1943 departed Kure for Singapore to pick up a cargo of tin, tungsten, zinc, rubber and quinine. She departed Singapore in December 1943 for Nazi-occupied France, and reached the Bay of Biscay in March 1944. She was escorted by German warships and aircraft and came under heavy attack by Allied aircraft, but arrived safely at Lorient. I-29 departed Lorient in April 1944 with considerable German technology, including a Walter rocket engine and plans for the jet-powered Me 262 and the rocket-powered Me 163. She arrived at Singapore in July, but was sunk with her cargo en route to Japan in the Luzon Strait by the American submarine USS Sawfish on 26 July 1944. In March 1944 left Kure with a cargo of metals, including gold, and a team of technicians who were to study German anti-aircraft techniques, stopping at Singapore to pick up other cargo. I-52 reached the South Atlantic and successfully rendezvoused with U-530 on 23 June to embark a German liaison officer, two radio operators, the current German naval code and a Naxos radar detector. However, that night she was detected by radar-equipped Grumman TBF Avenger aircraft from an American hunter-killer group centered on the escort carrier USS Bogue, which dropped sonobuoys and "Fido" homing torpedoes, sinking I-52 with all hands near, west of the Cape Verde Islands. It is believed that on her return voyage to Japan she would have been carrying uranium oxide. I-52's voyage was the last Yanagi mission undertaken by the IJN.
Reciprocal voyages
The GermanU-boat arm made several reciprocal exchange voyages, though these were outside the Yanagi scheme; they also made a number of blockade-running voyages, also separate from the Yanagi missions. From February to June 1943 sailed to the Indian Ocean, meeting with I-29 in the Mozambique Channel. U-180 transferred Subash Chandra Bose, future leader of the Indian National Army, and received two tons of gold in payment for German goods so far received. In May 1943 sailed for Japan, arriving in Kure in August. Code-named 'Marco Polo I' she was transferred to the IJN as an exchange in submarine technology, and was commissioned by them as RO-500. In February 1944, code-named 'Marco Polo II', was transferred to the IJN at Kiel, commissioned as RO-501 and sailed with a Japanese crew. She was intercepted and sunk west of the Cape Verde islands by the hunter-killer group. In February 1945 sailed from Norway under Operation Caesar; she was detected and sunk by the British submarine HMS Venturer in the Norwegian Sea. In March 1945 sailed for Japan, the last attempt to be made, but she was overtaken by the German surrender and was taken into custody by the USN off Newfoundland.
