IJN Subchaser CH-40:
Tabular Record of Movement
© 2005-2013 Bob Hackett, Sander Kingsepp and Peter Cundall
18 February 1942:
Innoshima. Laid down at the Hitachi Zosen K.K. shipyard.
10 November 1942:
Launched and numbered CH-40.
31 March 1943:
Completed and assigned to the Yokosuka Guard Force. Patrols the Ise, Aomori, Iwate, and Miyagi areas and escorts convoys.
15 April 1943:
Arrives at Tokyo Bay escorting convoy 7415 consisting of GINYO, RYOTOKU, RYUA, TAISHO and HEIWA MARUs and SEIZAN MARU No. 2 and an unidentified merchant ship. The convoy originally sailed from the Inland Sea.
5 September 1943:
Reassigned to SubChasDiv 23 of the 8th Base Force in Vice Admiral, the Baron, Samejima Tomoshige's (37)(former CO of NAGATO) 8th fleet at Rabaul. Escorts convoys between Rabaul, Palau and Truk.
13 September 1943:
Departs Yokosuka with Auxiliary sub-chasers CHa-23, CHa-29 and CHa-30 escorting SEIKAI MARU to Chichijima. At Chichijima CH-40 is detached.
3 October 1943:
CH-17 and CH-40 depart Rabaul escorting convoy O-302 consisting of two unidentified merchant ships.
11 October 1943:
Arrives at Palau.
14 October 1943:
CH-40 and CH-17 depart Palau escorting convoy So-406 consisting of ASUKA, RYUOSAN, TAGA, FUKKO, TAIRIN and HOKKAI MARUs.
18 October 1943:
At 0345, TAIRIN MARU is torpedoed and sunk by LtCdr (later Rear Admiral) John S. Coye's (USNA ’33) USS SILVERSIDES (SS-236) at 00-22N 143-23. The ship is on Army war service carrying Army tanks and vehicles and 2,100 tons of gasoline pumps and foodstuffs. Two gunners, and one Watchman and one crewman are killed.
21 October 1943:
The remainder of the convoy arrives at Rabaul.
31 October 1943:
CH-16 and CH-40 depart Rabaul escorting convoy O-104 consisting of FUKKO, TOYOOKA, OSUMI and ASUKA MARUs.
7 November 1943:
At 1500 arrives at Palau.
23 November 1943:
At 1400, CH-40 departs Truk escorting convoy No. 5233 consisting of NIPPO and CHOKO MARUs and NANKAI MARU No.2 (the latter towing "special" craft No. 35). The convoy later arrives at Kwajalein on 1 December. 
26 November 1943:
CH-40 departs Rabaul for Truk escorting a convoy consisting of ONOE and KAMOI MARUs and HOSHI MARU No. 5.
275 miles NW of Kavieng, New Ireland. At 2116, LtCdr (later Cdr) James W. Davis' (USNA ’30) torpedoes and sinks ammunition ship ONOE MARU at 00-40N 148-20E. One crewman is killed. CH-40 counterattacks, but is damaged by the explosion of her own depth charges. Four subsequent attempts by USS RATON to sink the remaining freighters are defeated by the escorts’ effective countermeasures.
27 November 1943:
At 0605, USN codebreakers intercept a message from CH-40 that reads: “Picked up captain and 195 members of the crew of ONOE MARU which sank at 2240. Headed for Truk at 0020 but could not use radio because of damage sustained while making depth charge attack.”
FRUMEL evidently intercepted the same signal, adding two additional sentences (2nd and 3rd):
"These included 14 wounded which were turned over to __. 1 officer and 12 men are missing."
1 December 1943:
At 0700, CH-40, CH-16, CH-20 and CH-29 depart Truk escorting convoy 1013 consisting of submarine tender NAGOYA MARU, transport YAMAKUNI MARU (ex YAMAKAZE MARU) and aircraft transport KEIYO MARU.
5 December 1943:
At 1510, arrives at Rabaul.
17 January 1944:
CH-40 and CH-16 depart Rabaul in convoy O-604 consisting of TAIAN, FRANCE and SHOUN MARUs.
23 January 1944:
At 1345, the convoy arrives at Palau.
28 January 1944:
At 1600, CH-40, CH-16, CH-34, CH-35 and auxiliary submarine chasers CHa-47 and CHa-61 depart Palau escorting convoy SO-805 consisting of TOEI and HOKKAI MARUs, oiler TAKATORI MARU No. 2, TAIEI and TOKO MARUs. The convoy is also given air cover.
30 January 1944:
At 0150, IJA freighter TOKO MARU, carrying troops of the 2nd Battalion, 66th Infantry Regiment, 51st Division and 4th Field Hospital to Manus Island in the Admiralties, is torpedoed by LtCdr (later Captain) Slade D. Cutter's (USNA ’35) USS SEAHORSE (SS-304) at 06-20N, 138-08E. TOKO MARU sinks by the stern taking down 464 troops and 15 crewmen.
1 February 1944:
IJN transport TOEI MARU, carrying drummed gasoline and ammunition, is sunk by USS SEAHORSE's last torpedoes at 04-24N, 143-15E. 56 crewmen are KIA. LtCdr Cutter makes for Pearl Harbor.
E 4 February 1944:
CH-40 arrives Rabaul.
18 February 1944:
CH-40 and CH-22 depart Rabaul for Moji escorting convoy O-902 consisting of SHINTO MARU No. 1 and TATSUGIKU MARU.
On that date, FRUMEL decrypts the following message from an unidentified sender:
"Convoy O-902 will leave Rabaul at 0001 on 19th and proceed hugging the coast of New Ireland. Departure from 1 mile east of Watom Island on course 330 degrees.
Composition: No. 1 SHINTO MARU and SHINKIKU MARU [sic] escorted by Subchasers 22 and 40."
19 February 1944:
22 miles N of Kavieng, New Ireland, near Kaut Bay. At about 1430, Fifth Air Force B-25s of the 345th Bomb Group's 500th and 501st Squadrons, A-20 "Havoc" light bombers of the 3rd Bomb Group and P-38 "Lightning" fighters attack and destroy convoy O-902. They sink CH-40 and CH-22 at 03-04S, 150-42E and cargo ships SHINTO MARU No. 1 and TATSUGIKU MARU at 02-46N, 150-42E. 15 of TATSUGIKU MARU's crew are killed. SHINTO MARU No. 1 was evacuating hundreds of ground personnel of the IJN 11th Air Fleet from Rabaul to Truk. 41 troops, 46 gunners and 19 crewmen are killed.
The USAAF's Fifth Air Force wipes out the entire convoy.
31 March 1944:
Removed from the Navy List.
 CH-40 apparently was detached from convoy No. 5233 and made port at Rabaul on or before 26 November.
Thanks go to John Whitman for info on CH-40's intercepted message and to Mr. Gilbert Casse of France for general assistance. Special thanks go to Hans Mcilveen of the Netherlands for info on FRUMEL intercepts.
-Bob Hackett, Sander Kingsepp and Peter Cundall.
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