IJN Submarine RO-501 (ex-U-1224):
Tabular Record of Movement

(RO-501 leaving Kiel, Germany)

© 2001-2017 Bob Hackett & Sander Kingsepp
Revision 4

30 November 1942:
Hamburg, Germany. A 1,144-ton (surfaced) type IXC/40 U-boat, is laid down at Deutsche Werft AG.

7 July 1943:
Launched and numbered U-1224.

31 August 1943:
Brest, France. LtCdr (Cdr, posthumously) Norita Sadatoshi (57)(former CO of I-122) and a 48-man spare crew arrive from Penang, Malaya aboard Cdr Uchino Shinji's I-8. Norita and his crew engage in customary sight-seeing in France. Upon completion of their liberty, they travel by train to U-boat training school facilities on the Baltic Sea where, for the next six months, the Germans train Norita and his crew in the handling, tactics and operations of a Type IXC/40 U-boat.

20 October 1943:
Completed and commissioned in the Kriegsmarine. Kapitänleutnant Georg Preuss is the Commanding Officer. [1]

October 1943-February 1944:
U-1224 is assigned to the 31st Flotilla for training.

15 February 1944 - German Operation "Marco Polo II":
Kiel, Germany. In a ceremony in a submarine pen, U-1224 is handed over to the IJN. The Japanese rename her "Satsuki (Month of First Buds) No. 2." [2] LtCdr Norita is the CO.

28 February 1944:
U-1224 is commissioned in the IJN as RO-501. RO-501 is assigned for training at the German U-boat anti-aircraft school at Swinemünde (now Swinoujscie, Poland) on the Baltic Sea.

28 March 1944:
Berlin, Germany. The future passengers of RO-501 depart for Kiel by train.

30 March 1944:
Kiel, Germany. At 0800, RO-501 departs, carrying a cargo of mercury, lead, steel, uncut optical glass and aluminum in her keel and drawings, models and blueprints necessary to construct a Type IXC U-boat. In addition to submarine-related materials there is a full set of Messerschmitt Me-163 "Komet" rocket interceptor blueprints. [3]

Captain (Rear Admiral, posthumously) Emi Tetsushiro (former CO of I-8) is among RO-501's four passengers. (In April 43, Emi traveled as a passenger aboard I-29 from Penang, then transferred to U-180 for France to observe German U-boat building techniques.) In addition to Emi, there is Constructor Captain Yamada Seiichi, Constructor Cdrs Nemoto Yuichiro and Yoshikawa Haruo. The 52-strong crew also includes two Germans--one radar operator and one pilot. The ETA at Penang is mid-July 1944.

31 March 1944:
Norway. At 2000, RO-501 arrives at Kristiansund-South submarine base to embark fuel and supplies.

1 April 1944:
At 1830 departs in company of U-859 under Kapitänleutnant Johann Jebsen.

11 May 1944:
LtCdr Norita sends a coded signal reporting that RO-501 passed the position 30N, 37W two days earlier and has been chased since then. His signal is detected by high frequency/direction finding ("Huff Duff") equipment aboard the hunter-killer group TG.22.2. It is the last signal received from RO-501. [4]

13 May 1944:
Atlantic Narrows, 500 miles W of the Cape Verde Islands. Lt John E. Johansen's FRANCIS M. ROBINSON (DE-220) is a member of Captain Aurelius B. Vosseller's USS BOGUE (CVE-9) hunter-killer group, TG.22.2, with four other destroyer escorts of CortDiv 51.

ROBINSON is on an ASW patrol making 17 knots and heading 200 degrees. At 1900 hours, ROBINSON's sonar operator detects a target that he classifies as a submarine at 825 yards. BOGUE turns away. Lt Johansen streams a "Foxer" (noisemaker) to decoy any possible acoustic-tracking torpedoes that the submarine may have fired.

ROBINSON fires a barrage of twenty-four ahead-thrown Mark 10 "Hedgehog" projector charges, followed by five salvos of Mark 8 magnetic influence depth charges. Four underwater explosions are heard and recorded. RO-501 sinks at 18-07'59N, 33-12'59W in 2,900 feet of water.

3 July 1944:
FRUMEL decodes the German Naval Attache's query dated with 2 July regarding the fate of SATSUKI No. 2. The query notes that Berlin had been out of communication with U-1224 before 7 June.

26 August 1944:
Presumed lost with all hands in the Indian Ocean.

10 October 1944:
Removed from the Navy list.

Authors' Notes:
[1] Some accounts list Preuss as lost with U-511/RO-500 on 13 May 1944, but this is incorrect as he took command of U-875 on 21 April 1944.

[2] Satsuki No. 1 was U-511/RO-500.

[3] One of three sets set of Me-163 blueprints; the others were carried aboard I-29 and U-511.

[4] The USN plotted RO-501's course and estimated that on 22 June 1944 she would be off Capetown, South Africa at 41S, 26E. Codebreaker's also intercepted transmissions indicating that RO-501 was to be refueled by I-8 in the Indian Ocean. As late as 22 June 1944, the USN was unaware they have already sunk RO-501.

Thanks go to Dr. Higuchi Tatsuhiro of Japan. Special thanks for assistance in researching the IJN officers mentioned in this TROM go to Mr. Jean-François Masson of Canada.

-Bob Hackett and Sander Kingsepp.

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