Wreck of HIJMS RO-501/U-1224

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Laid down in November 1942 as a Type IXC/40 Unterseeboot at the Deutsche Werft Shipyard in Hamburg, the U-1224 commissioned into service with the Kriegsmarine in October 1943. After taking on a skeleton crew of German sailors, the U-1224 took aboard a full crew of 48 sailors from the Imperial Japanese Navy and began intensive training in the Baltic Sea. After instructing the IJN sailors on the operation of the onboard systems of the U-boat, the U-1224 was formally decommissioned by the Kriegsmarine on February 15th, 1944 and was transferred to the Imperial Japanese Navy, commissioning as the HIJMS RO-501 on February 28th.

After another month of training in the Baltic with her new crew, the RO-501 prepared to depart Kiel for the long journey back to Japan by way of the Cape of Good Hope and the Indian Ocean. Taking aboard a secret cargo of precious metals, uncut optical glass and drawings, models and blueprints necessary to construct a Type IXC U-boat in addition to a full set of Messerschmitt Me-163 "Komet” rocket interceptor blueprints, the crew was joined by a Japanese Captain and Engineer who had been studying U-boat construction for over a year and two Germans; a radar operator and one pilot. Standing out of Kiel on March 30th with an ETA at Penang in Malaysia in mid-July 1944 the RO-501 cleared the English Isles and made for the Azores.

Refueling from the 'milk cow' U-boat U-488 off the Azores in late April, the RO-501 and her crew resumed their voyage and prepared for the long leg around Africa. Surfacing on May 6th to recharge her badly depleted batteries following two days spent underwater due to Allied warships, the Captain of the RO-501 dispatched a coded message to Imperial Fleet Command reporting her position and status, but was unaware his message was received and decoded by the nearby US Navy hunter-killer group centered around the Escort Carrier USS Bogue (CVE-9), which quickly responded to the given coordinates and began hunting for the RO-501.

After days of searching for the illusive submarine without result, sonar operators aboard the Destroyer Escort USS Francis M. Robinson (DE-220) were quick to report what they later confirmed to be a submerged contact at 1900hrs on May 13th while their ship was performing an ASW sweep ahead of its carrier. Once the contact was confirmed, the Robinson was directed to attack by the Bogue's commander as the Carrier was swung into the wind and made ready to launch its aircraft if needed. Closing over the deep-running RO-501, the Robinson fired a 24-mortar spread from its 'hedgehog' mount onto the contact, followed shortly thereafter by a string of eight depth charges.

All of the munitions detonated as intended around the submerged contact but no debris was brought to the surface so the Robinson came around to make a second attack. As she did, four large separate explosions were heard in the deep, followed by a gradual loss of contact with the submarine, indicating the loss of the RO-501 and all 52 men aboard her in 2,900ft of water on May 13th, 1944.

uboat.net/boats/u1224.htm
www.combinedfleet.com/RO-501.htm

 Second World War 1939-1945shipwrecksubmarine