Nazi Germany
Name: U-1224
Ordered: 25 August 1941
Builder: Deutsche Werft, Hamburg
Yard number: 387
Laid down: 30 November 1942
Launched: 7 July 1943
Commissioned: 20 October 1943
Decommissioned: 15 February 1944
Fate: Transferred to Japanese service
Notes: Used as a training ship for Japanese crew
Name: RO-501
Acquired: 15 February 1944
In service: 15 February 1944
Fate: Sunk, 13 May 1944
General characteristics
Class and type: Type IXC/40 submarine
  • 1,144 t (1,126 long tons) surfaced
  • 1,257 t (1,237 long tons) submerged
  • 6.86 m (22 ft 6 in) o/a
  • 4.44 m (14 ft 7 in) pressure hull
Height: 9.60 m (31 ft 6 in)
Draught: 4.67 m (15 ft 4 in)
Installed power:
  • 4,400 PS (3,200 kW; 4,300 bhp) (diesels)
  • 1,000 PS (740 kW; 990 shp) (electric)
  • 18.3 knots (33.9 km/h; 21.1 mph) surfaced
  • 7.3 knots (13.5 km/h; 8.4 mph) submerged
  • 13,850 nmi (25,650 km; 15,940 mi) at 10 knots (19 km/h; 12 mph) surfaced
  • 63 nmi (117 km; 72 mi) at 4 knots (7.4 km/h; 4.6 mph) submerged
Test depth: 230 m (750 ft)
Complement: 4 officers, 44 enlisted
Service record[1]
Part of:
  • Kptlt. Georg Preuss
  • 20 October 1943 - 15 February 1944
Operations: None
Victories: None

German submarine U-1224 was a Type IXC/40 U-boat of Nazi Germany's 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 15 February 1944. In the Imperial Japanese Navy, she served as RO-501 until sunk May 1944.


German Type IXC/40 submarines were slightly larger than the original Type IXCs. U-1224 had a displacement of 1,144 tonnes (1,126 long tons) when at the surface and 1,257 tonnes (1,237 long tons) while submerged.[2] The U-boat had a total length of 76.76 m (251 ft 10 in), a pressure hull length of 58.75 m (192 ft 9 in), a beam of 6.86 m (22 ft 6 in), a height of 9.60 m (31 ft 6 in), and a draught of 4.67 m (15 ft 4 in). The submarine was powered by two MAN M 9 V 40/46 supercharged four-stroke, nine-cylinder diesel engines producing a total of 4,400 metric horsepower (3,240 kW; 4,340 shp) for use while surfaced, two Siemens-Schuckert 2 GU 345/34 double-acting electric motors producing a total of 1,000 shaft horsepower (1,010 PS; 750 kW) for use while submerged. She had two shafts and two 1.92 m (6 ft) propellers. The boat was capable of operating at depths of up to 230 metres (750 ft).[2]

The submarine had a maximum surface speed of 18.3 knots (33.9 km/h; 21.1 mph) and a maximum submerged speed of 7.3 knots (13.5 km/h; 8.4 mph).[2] When submerged, the boat could operate for 63 nautical miles (117 km; 72 mi) at 4 knots (7.4 km/h; 4.6 mph); when surfaced, she could travel 13,850 nautical miles (25,650 km; 15,940 mi) at 10 knots (19 km/h; 12 mph). U-1224 was fitted with six 53.3 cm (21 in) torpedo tubes (four fitted at the bow and two at the stern), 22 torpedoes, one 10.5 cm (4.13 in) SK C/32 naval gun, 180 rounds, and a 3.7 cm (1.5 in) Flak M42 as well as two twin 2 cm (0.79 in) C/30 anti-aircraft guns. The boat had a complement of forty-eight.[2]

FLAK weaponry

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.

Service history


The submarine's keel was laid down on 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.

Dai-Nippon Teikoku Kaigun (Imperial Japanese Navy)

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 (ref. 2), 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.

Technology Transfer

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 (ref. 4).

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.

Loss at Sea

The intended route to Malaysia was to take RO-501 to the Azores for refueling, and then around the Cape of Good Hope. Along the way, RO-501 ran into an anti-submarine patrol group including the Escort Carrier USS Bogue and the Destroyer Escort USS Francis M. Robinson. The patrol drove 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 19:00 on 13 May 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 four underwater explosions were detected. All 52 men aboard RO-501 were believed killed (the 48 crew who had trained on it, 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 2,900 feet (880 m) of water at 18°7′59″N 33°12′59″W / 18.13306°N 33.21639°W / 18.13306; -33.21639Coordinates: 18°7′59″N 33°12′59″W / 18.13306°N 33.21639°W / 18.13306; -33.21639. The site is rarely dived due to its extreme depth, which is well beyond skinsuit range.


  1. ^ Helgason, Guðmundur. "The Type IXC/40 boat U-1224". German U-boats of WWII - uboat.net. Retrieved 16 October 2014.
  2. ^ a b c d Gröner 1991, p. 68.


  • Busch, Rainer; Röll, Hans-Joachim (1999). German U-boat commanders of World War II : a biographical dictionary. Translated by Brooks, Geoffrey. London, Annapolis, Md: Greenhill Books, Naval Institute Press. ISBN 1-55750-186-6.
  • Busch, Rainer; Röll, Hans-Joachim (1999). Deutsche U-Boot-Verluste von September 1939 bis Mai 1945 [German U-boat losses from September 1939 to May 1945]. Der U-Boot-Krieg (in German). IV. Hamburg, Berlin, Bonn: Mittler. ISBN 3-8132-0514-2.
  • Gröner, Erich; Jung, Dieter; Maass, Martin (1991). U-boats and Mine Warfare Vessels. German Warships 1815–1945. 2. Translated by Thomas, Keith; Magowan, Rachel. London: Conway Maritime Press. ISBN 0-85177-593-4.

External links

  • Wreck information for the RO-501
  • German Sub Losses
  • Helgason, Guðmundur. "The Type IXC/40 boat U-1224". German U-boats of WWII - uboat.net. Retrieved 7 December 2014.
  • Blockade Running Information, WW2