SOKAITEI!

© 2009 Bob Hackett and Peter Cundall

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20 September 1940:
Harima. Laid down at Harima Shipbuilding.

28 February 1941:
Launched and numbered W-21.

30 June 1942:
Completed and commissioned in the IJN. Lt Sakae Moriyasu is the Commanding Officer.

9 May 1943:
W-21 departs Takao escorting convoy No. 748 consisting of six unidentified merchant ships.

13 May 1943:
Arrives at Manila.

10 December 1943:
Truk. At 1230, W-21 departs Truk for Rabaul with minesweeper W-22 and auxiliary submarine-chaser CHa-48 escorting convoy No. 1103 consisting of NIKKO and KIMISHIMA MARUs and SHINSEI MARU No. 18. NIKKO MARU is towing an unidentified midget submarine and KIMISHIMA MARU is towing a midget supply submarine.

15 December 1943:
At 0810, SHINSEI MARU No. 18 that suffered navigational troubles a few days earlier leaves the convoy with W-22 and CHa-48 and heads for Kavieng, New Ireland. At 1210, the same day, the rest of the convoy is attacked by American aircraft, but incurs no damage.

16 December 1943:
At 1336, the remainder of convoy No. 1103, including the midget submarine and the tokugata unkato midget supply submarine, arrive at Rabaul.

25 December 1943:
Kavieng. Aircraft from Rear Admiral (later Admiral) Frederick C. Sherman’s (former CO of LEXINGTON, CV-2) TG 50.2's BUNKER HILL (CV-17) and MONTEREY (CVL-26) attack and sink transport TENRYU MARU and damage W-21, minesweeper W-22 and KIYOSUMI MARU.

28 December 1943:
At 0945, USN codebreakers intercept and decrypt a message from the CO of W-21 that reads: “Nine enlisted men reported as killed in action at 0605, 25 December in ----- area.” [1]

6 March 1944:
At 1130, W-21 departs Truk escorting convoy No. 4304 consisting of URAKAMI, SHIRANE, JUZAN and AWAJI MARUs also escorted by kaibokan AMAKUSA and MIKURA and subchaser CH-33.

10 March 1944:
At 1222, arrives at Saipan.

14 March 1944:
At 1540, W-21 departs Saipan with subchasers CH-18 and CH-17 escorting convoy No. 4313-B consisting of JUZAN and SHIRANE MARUs and SEIKAI MARU No. 1. JUZAN MARU is towing damaged SANTO MARU.

17 March 1944:
At 1200, CH-18 and CH-17 are detached.

20 March 1944:
The convoy arrives safely at Chichi-Jima.

June 1944:
Lt Shigeru Ujihara assumes command.

19 August 1944:
At 0600, W-21 departs Moji with minelayer SHIRATAKA, destroyers WAKABA, HIBIKI (and probably HATSUHARU) escorting convoy MI-15 consisting of URATAO, RIKKO, CHIYODA, EKKAI, TAISHO, HOKUSEN, TSINGTAO, TOSHIGAWA and NANSEI MARUs and OKINOYAMA MARU No. 5.

25 August 1944:
Arrives at Takao at 1600.

30 August 1944:
At 1500, W-21 departs Takao for Manila with minelayer SHIRATAKA, kaibokan CD-10 and CD-20 escorting reorganized convoy MI-15 that now consists of RIKKO, TAISHO, OKUNI (TAIKOKU) Maru, EIKYU, SHINYO, NANSEI, HOSEN and CHIYODA MARUs with UNKAI MARU No. 5, OKINOYAMA MARU No. 5 and KYOEI MARU No. 10.

31 August 1944:
Luzon Strait, S of Formosa. At about 0220, LtCdr (later Rear Admiral) Charles E. Loughlin's QUEENFISH (SS-393) hits CHIYODA MARU with four torpedoes and sets her afire. At 0240, CHIYODA MARU sinks. Loughlin also damages oiler RIKKO MARU steaming in ballast.

LtCdr (later Vice Admiral) Eli T. Reich's USS SEALION (SS-315), a member of "Ben's Busters" with GROWLER (SS-215) and PAMPANITO, enters the Bashi Strait. SEALION’s SJ radar picks up the convoy. Reich makes a night surface approach. He sets up and fires six torpedoes, but they all run erratically. About 0500, Reich swings SEALION and fires four stern torpedoes at a large tanker. He claims two hits.

Alerted by code-breaker's "Ultra" signals, LtCdr (later Rear Admiral) Eugene B. Fluckey's USS BARB (SS-220) intercepts the convoy. At about 0700, Fluckey torpedoes OKUNI MARU. She sinks stern first. Fluckey also sinks the 45th Minesweeper Squadron's HINODE MARU No. 20 that was patrolling the area.

SEALION evades the convoy's escorts. Still surfaced, LtCdr Reich makes an “end-around” approach and works his way ahead of the convoy. Reich misidentifies minelayer SHIRATAKA as a destroyer. He begins a submerged approach. At 0730, Reich hits SHIRATAKA with two of three torpedoes. At 1115, SHIRATAKA sinks at 20-55N, 121-07E.

7 September 1944:
At 1000, the convoy arrives at Manila.

26 October 1944:
At 1730, fleet stores ship MAMIYA departs Mutsure in convoy HI-79 consisting of transports KAGU, MELBOURNE and ARIMASAN MARUs and tankers TENEI and MATSUSHIMA MARUs. The ships are initially escorted by light cruiser KASHI, kaibokan NOMI, UKURU and minelayer NIIZAKI.

27 October 1944:
Kaibokan CD-17 joins the escort.

28 October 1944:
W-21 joins the escort.

29 October 1944:
MELBOURNE MARU is detached for Keelung escorted by UKURU and CD-17.

30 October 1944:
HI-79 arrives at Takao. W-21, MAMIYA and KAGU MARU are detached.

4 November 1944:
At 1826, USN codebreakers intercept and decrypt a message from W-21 that reads: “At 1745 [Transport No. 111] torpedoed---- sunk--- request replenishment 15-56N, 119-44E.” [2]

At 2025, codebreakers decrypt another message that reads: “Coast Defense Ships No. 18 and No. 26 will sortie at once from Manila and hasten to scene of disaster (15-56N, 119-44 E) where they will engage in salvage (towing).”

14 January 1945:
W-21 departs Takao with destroyer ASAGAO, kaibokan YASHIRO, CD-1, CD-130, CD-134 and CD-56 escorting convoy TAMO-37 consisting of seven unidentified merchant ships.

23 January 1945:
Arrives at Moji.

14 February 1945:
W-21 departs Moji with kaibokan CD-50 and two other unidentified warships escorting convoy MOTA-37 consisting of five unidentified merchant ships.

E 15 February 1945:
W-21 is detached and returns to Moji.

16 February 1945:
W-21 departs Moji with destroyer TSUBAKI, kaibokan CD-39, CD-55 and CD-82 escorting convoy MOTA-38 consisting of five unidentified merchant ships.

23 February 1945:
Arrives at Kirun.

10 April 1945:
East of the mouth of the Yangtze River, China. W-21 is damaged by a mine laid by USAAF B-29s on 4 and 28 March.

May 1945:
Lt Yuji Ado assumes command.

15 August 1945:
W-21’s crew learns of the end of hostilities.

25 October 1945:
Removed from the Navy List.

1 October 1947:
Ceded to the United States as a war reparation. Thereafter, scrapped.

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Authors' Note:
[1] CNO analysts say “W-21 appears to have gone to Rabaul about the middle of January and thence to Truk. On 29 February 1944 she was ordered to return to the Empire for repairs which appear to have been completed about 15 April.”

[2] T.111 was not sunk on 4 Nov '44, but only damaged by a torpedo probably fired by USS SAILFISH (SS-192). T.111 was finally sunk on 24 Nov '44 by aircraft.

Thanks go to John Whitman of the USA for info on CNO intercepts of Japanese messages.

-Bob Hackett and Peter Cundall.

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