German submarine U-1224

U-1224/RO-501 was mounted with a single 3.7 cm Flakzwilling M43U gun on the LM 42U mount. The LM 42U mount was the most common mount used with the 3.7 cm Flak M42U. The 3.7 cm Flak M42U was the marine version of the 3.7 cm Flak used by the Kriegsmarine on Type VII and Type IX U-boats.

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  A single 3.7 cm Flak M42U gun on the LM 42U mount.

The submarine's keel was laid down in November 1942 by Blohm & Voss of Hamburg. It 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 Japanese sailors at sea from October 1943 to February 1944.

After the crew underwent 3 months of training, U-1224 was recommissioned into the Japanese navy under the pennant RO-501. Captain Narita was put in charge of the crew, and 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.

Germany and Japan were separated by great distance, and by 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.

On its journey from Germany to Malaysia, 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.

The intended route to Penang was to take RO-501 through the middle of the Atlantic Ocean west of the Azores and the Cape Verde islands, then around the Cape of Good Hope. She was to rendezvous with I-8 in the Indian Ocean to refuel before proceeding to her destination.[3] However, at 30°0′0″N 37°0′0″W, RO-501 ran into a U.S. Navy hunter-killer group comprising escort carrier USS Bogue and five destroyer escorts, including USS Francis M. Robinson . The group's presence forced RO-501 underwater for two days, during which her batteries were depleted and her captain radioed a coded signal that he was being pursued.[3] Unfortunately, this transmission was detected by the American ships with their high-frequency direction finding ("Huff-Duff") equipment, which enabled them to pinpoint the submarine's location.

The Francis M. Robinson reported a submerged contact at 19:00 on 13 May 1944. The destroyer escort engaged the contact with a full salvo from its forward-throwing Hedgehog mount, followed by five salvos of magnetic proximity fuzed depth charges. Four underwater explosions were detected. All 56 hands aboard were lost - 52 crew (including a German radar operator and a German pilot) plus four IJN officer passengers.

The final resting place of U-1224/RO-501 is 500 nm WNW of the Cape Verde islands at 18°7′59″N 33°12′59″W in 2,900 feet (880 m) of water.