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

(RO-501 leaving Kiel, Germany)

© 2001-2012 Bob Hackett & Sander Kingsepp
Revision 3

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 Norita Sadatoshi (57)(former CO of I-122) and a 48-man spare crew arrive from Penang, Malaya aboard Cdr Uchino Shinichi'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]

28 February 1944:
U-1224 is commissioned in the IJN as RO-501. LtCdr Norita is the CO. 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. 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 Captain Engineer Yamada Seiichi and two other engineers. The crew also includes two Germans--one radar operator and one pilot. The crew is 52 men strong. The ETA at Penang is mid-July 1944.

Early April 1944:
Norway. RO-501 arrives at Kristiansund-South submarine base to embark fuel and supplies. Departs in company of U-859 under Kapitänleutnant Johann Jebsen.

Late April 1944:
W of Azores. Refuels from U-488.

6 May 1944:
LtCdr Norita sends a coded signal from a planned reporting position at 30N, 37W and adds that his boat had been forced underwater two days earlier. The signal is detected by high frequency/direction finding ("Huff Duff") equipment aboard a hunter-killer group. 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 18-08N, 33-13W 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 No. 2 SATSUKI. 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. LtCdr Norita is posthumously promoted Cdr and Captains Emi and Yamada are both posthumously promoted Rear Admiral.

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 '44, but this is incorrect as he took command of U-875 on 21 Apr '44.

[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 plots RO-501's course and estimates that on 22 June 1944 she will be off Capetown, South Africa at 41S, 26E. Codebreaker's also intercept transmissions that indicate RO-501 will be refueled by I-8 in the Indian Ocean. As late as 22 Jun '44, the USN is unaware they have already sunk RO-501.

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

-Bob Hackett and Sander Kingsepp.

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