German submarine U - 1224 German submarine " U - 1224 " was a Type IXC / 40 U - boat of the German " Kriegsmarine " built for service during World War II . She was constructed by Deutsche Werft of Hamburg , used as a training ship for Japanese sailors , and transferred into Japanese service on February 15 , 1944 . Service history . Kriegsmarine ( German Navy ) . His keel was laid down on November 1942 by Blohm + Voss of Hamburg . He was commissioned in October 1943 . " U - 1224 " was used as a training ship for Japanese sailors , and engaged in technology transfer activities . It began its career doing training for Japanese sailors in the Baltic Sea . A small crew of Kriegsmarine Sailors trained 48 IJN sailors at sea from October 1943 to February 1944 . Dai - Nippon Teikoku Kaigun ( Imperial Japanese Navy ) . After the crew underwent 3 months of training , the U - 1224 was recommissioned into the Japanese navy under the pennant ' RO - 501 ' . Captain Narita was put in charge of the crew ( ref . 2 ) , and the ' RO - 501 ' was then tasked to carry a load of war materials , blueprints , and other secret cargo from Kiel , Germany to Penang , Malaysia . The mission was never completed . Technology Transfer . Germany and Japan were separated by great distance , and in early 1944 they were increasingly cut off from each other . While neither power was able to send meaningful reinforcements or armaments through territory controlled by the Allied powers , they were able to use submarines to share some intelligence and weapons blueprints . Submarines offered security and their stealth allowed for a fair chance of success . Between 1942 and 1944 , approximately 35 submarines attempted the journey from Europe to the Far East , and at least 11 attempted the journey from the Far East to Europe ( ref . 4 ) . On its journey from Germany to Malaysia , the RO - 501 carried precious metals , uncut optical glass , models and blueprints necessary to construct a Type IX U - boat in addition to motors and blueprints for the Messerschmitt Me - 163 " Komet ” rocket fighter airplane . It was also hoped that the trained Japanese sailors would pass along their expertise . Loss at Sea . The route to Malaysia took the " RO - 501 " to the Azores for refueling , and then around the Horn of Africa . Along the way , the RO - 501 ran into an anti - submarine patrol group including the Escort Carrier and the Destroyer Escort . The patrol drove the RO - 501 underwater for 2 days , during which its batteries were depleted and the Captain radioed a distress signal to Imperial Fleet Command . The Allies had broken the code , and the message helped the Allied hunter - killer group close in on the submarine . The " Francis M . Robinson " reported a submerged contact at 1900 hours on May 13 , 1944 . The destroyer engaged the contact with a 24 - mortar spread from its hedgehog mount , and then dropped a string of eight depth charges . Shortly after the munitions detonated , a series of 4 underwater explosions were detected . All 52 men aboard the RO - 501 were believed KIA ( the 48 crew who had trained on him , plus the Captain , an Engineer , a German pilot , and a German radar operator ) . The final resting place of " U - 1224 " / " RO - 501 " is south of the Azores in about of water at . The site is rarely dived due to its extreme depth , which is well beyond skinsuit range .