IJN Subchaser CH-23:
Tabular Record of Movement
© 2005-2013 Bob Hackett, Sander Kingsepp and Peter Cundall
Laid down at the Harima shipyard.
30 June 1941:
Numbered CH-23. Tentatively assigned to Sasebo Naval District.
13 August 1941:
15 November 1941:
Completed and registered in the Yokosuka Naval District.
18 December 1941:
Conducts antisubmarine patrols in Tokyo Bay.
15 May 1942:
Assigned directly to the Combined Fleet and attached to SubChasDiv 23.
11 June 1942:
Arrives at Guadalcanal.
14 July 1942:
Reassigned to Vice Admiral Mikawa Gunichi's (38) Eighth Fleet with the 7th Base Force's SubChasDiv 23 at Lae, New Guinea. Escorts convoys between Rabaul and the Solomon Islands.
17 August 1942:
CH-23 departs Rabaul for Basuba (Basabua) with light cruiser TENRYU, subchasers CH-22, CH-24 and minesweeper W-20 escorting a convoy consisting of KAZUURA, RYOYU and KANYO MARUs transporting the 25th Air Flotilla's base supplies.
18 August 1942:
At 1730, arrives at Basuba.
1 September 1942:
CH-23 departs Basuba escorting empty transport/AA ship YASUKAWA MARU and meets up en route with CH-23 escorting RYOYO and KAZUURA MARU.
4 September 1942:
Arrives at Rabaul.
11 September 1942:
Refueled by auxiliary seaplane tender KIYOKAWA MARU.
22 January 1943:
CH-23 and torpedo boat HIYODORI depart Rabaul escorting transport TOA MARU No. 2 on a troop transport run to Kolombangara, Guadalcanal.
28 January 1943:
CH-23 departs Rabaul with minelayer KAMOME and torpedo boat HIYODORI escorting troop transport TOA MARU No.2 GO to Kolambangara.
E 29 January 1943:
At some point probably off Bougainville Island KAMOME is detached.
30 January 1943:
Off Gizo the convoy comes under attack from US Navy aircraft. TOA MARU No.2 GO is hit by two bombs and is abandoned and finally sinks in 07.43S 156.51E. Nearly all 107 troops on board are rescued and only one crewman and two soldiers are KIA. Also lost are two light tanks, a side-car motorcycle and a cargo of cement and ammunition.
22 February 1943:
CH-23 departs Palau escorting TAMATSU and KOFUKU MARUs to Rabaul.
28 February 1943:
NE of Manus, Admiralty Islands. At 1138, the convoy is attacked unsuccessfully by a submarine, probably USS ALBACORE (SS-218), at 01-29S, 147-38E.
4 March 1943:
At 0200 arrives at Rabaul.
7 March 1943:
At 1500 departs Rabaul on a short escort mission.
8 March 1943:
At 1610 arrives back at Rabaul.
12 March 1943:
At 1515 CH-23 and CH-24 depart Rabaul on convoy escort mission.
22 March 1943:
At 0550 both escorts arrive back at Rabaul.
23 March 1943:
At 0430 departs Rabaul on convoy escort mission. At 1950 arrives back at Rabaul.
24 March 1943:
At 1500 departs Rabaul on an escort mission.
28 March 1943:
At 0730 CH-23 and minesweeper W-21 both arrive back at Rabaul.
29 March 1943:
At 1345 CH-23 and minesweeper W-21 depart Rabaul on an escort mission.
6 April 1943:
At 0725 arrives back at Rabaul.
7 April 1943:
At 1440 departs Rabaul on an escort mission.
10 April 1943:
At 1200 arrives back at Rabaul.
13 April 1943:
At 1300 departs Rabaul in convoy consisting of KAIFUKU, TOKO MARUs, YOSHIDA MARU No. 3 and one unidentified merchant ship also escorted by W-20 
1 May 1943:
At 1200 arrives back at Rabaul probably escorting a convoy from Palau consisting of SORACHI, HAMBURG, HIMALAYA and MEIZAN MARUs.
9 May 1943:
At 1530 CH-23 and CH-38 depart Rabaul for Palau escorting convoy R-09 consisting of YODOGAWA, CHOKO, YAMABUKI, FUKKO, NIKKI, TATEISHI MARUs and BANSHU MARU No. 15.
11 May 1943:
NE of Manus. At 0730, that same day, YODOGAWA MARU is hit by two torpedoes fired by LtCdr (later Rear Admiral) Edward C. Stephan's (USNA ’29) USS GRAYBACK (SS-208) at 00-40N, 148-55E. YODOGAWA MARU is set afire and sinks. Two crewmen are KIA.
17 May 1943:
Arrives at Palau.
20 May 1943:
CH-23 and CH-38 depart Palau escorying a convoy consisting of KOYU, TAISHO and MACASSAR MARUs.
28 May 1943:
At 0850 arrives at Rabaul. Later that day at 1500 departs Rabaul on an escort mission.
2 June 1943:
At 0430 arrives at Rabaul.
6 June 1943:
At 0430 departs Rabaul on an escort mission, probably escorting Army landing craft depot ship transport NIGITSU MARU part way to Palau.
10 June 1943:
At 1740 CH-18 and CH-23 arrive back at Rabaul together.
13 June 1943:
At 1740 CH-23 and CH-39 depart Rabaul on an anti submarine sweep.
15 June 1943:
At 0400 CH-23 arrives back at Rabaul.
16 June 1943:
At 1150 CH-16, CH-23 and CH-39 depart Rabaul escorting convoy 609 consisting of ADEN, TAIKO, HOFUKU, YAMAFUKU, SHINYUBARI and KURAMASAN MARUs and one other unidentified ship. CH-16 detaches en route and returns to Rabaul.
23 June 1943:
Arrives at Palau.
26 June 1943:
Departs Palau with CH-39 escorting convoy So-626 consisting of DAKAR, BUNZAN, TOHO and KINSEN MARUs and three unidentified merchant ships.
3 July 1943:
At 0530 arrives at Rabaul.
4 July 1943:
At 1600 departs Rabaul on an escort mission.
10 July 1943:
At 0818 arrives back at Rabaul.
16 July 1943:
At 1400 departs Rabaul on an escort mission, possibly escorting tanker SHINKOKU MARU.
28 July 1943:
CH-10, CH-18 and CH-23 depart Palau escorting convoy So-807 consisting of EHIME, KAZAN and KOZAN mARUs and two unidentified merchant ships.
5 August 1943:
At 0825 arrive at Rabaul.
5 August 1943:
At 0825 arrives back at Rabaul.
9 August 1943:
Departs Rabaul on patrol.
10 August 1943:
CH-23 is appointed the flagship of SubChasDiv 23.
11 August 1943:
At 1240 arrives back at Rabaul.
13 August 1943:
At 0640 departs Rabaul on patrol.
15 August 1943:
At 0820 arrives back at Rabaul.
18 August 1943:
At 0600 departs Rabaul on patrol.
20 August 1943:
At 0825 arrives back at Rabaul.
22 August 1943:
At 0200 departs Rabaul on patrol.
24 August 1943:
At 0830 arrives back at Rabaul.
27 August 1943:
At 0645 departs Rabaul on patrol.
29 August 1943:
At 0810 arrives back at Rabaul.
30 August 1943:
At 1015 departs Rabaul on patrol.
31 August 1943:
At 1500 arrives back at Rabaul.
1 September 1943:
At 1330 departs Rabaul on patrol.
2 September 1943:
At 0020 returns to Rabaul.
3 September 1943:
At 0653 CH-22 and CH-23 depart Rabaul on an escort mission.
5 September 1943:
At 0640 CH-23 arrives back at Rabaul.
9 September 1943:
At 0630 departs Rabaul on an escort mission.
12 September 1943:
At 1400 arrives at Rabaul. At 2230 departs Rabaul again on a further escort mission.
16 September 1943:
At 0800 arrives at Rabaul. At 1640 departs Rabaul again on a further escort mission.
19 September 1943:
At 0800 arrives back at Rabaul.
20 September 1943:
At 0700 departs Rabaul on an escort mission.
27 September 1943:
At 0715 arrives at Rabaul.
8 October 1943:
CH-23 and CH-24 depart Palau escorting convoy SO-806 consisting of KANAYAMASAN, HOZUGAWA, NITTAI, KAZAN, KIBI and KOSEI MARUs and SHINTO MARU No. 1.
15 October 1943:
Arrives at Rabaul.
18 October 1943:
Vunapope, near Rabaul. Six North American B-25D "Mitchell" medium bombers of the 345th Bomb Group's 500th Squadon attack and damage shipping in the bay including IJA cargo-passenger ship JOHORE MARU and two other unidentified freighters. CH-23 is underway in nearby St. George's Channel when 1st Lt Thane C. Hecox's B-25-D drops two 1,000-lb bombs and blows off her bow.
CH-23 is beached to avoid sinking. Later, she receives emergency repairs, probably by repair ship YAMABIKO MARU and others.
18 December 1943:
At 1400, CH-23 departs Kavieng escorting a convoy consisting of KANAIYAMA and KYUTOKUSAN MARUs.
19 December 1943:
At 1500, arrives at Rabaul.
1 January 1944:
On that day, FRUMEL decrypts two messages from CH-23, one timed 010135:
"At 0005 today KINSEISAN [KANAIYAMA] MARU was bombed and sunk as result of a near miss"
and another timed 011608:
"Have taken survivors of KINSEISAN [KANAIYAMA] MARU onboard and will leave Lorengau at 1800. Will anchor in Bakhateri Harbour from 1600 on 2nd till 0400 on 3rd and arrive Rabaul at 1630 on 3rd."
23-24 February 1944:
Truk. CH-23, auxiliary minelayer MINSEI MARU and special minesweepers No. 5 and No. 6, in cooperation with aircraft of the 902nd Naval Air Group, conduct anti-submarine operations near the Uligar and Salat Passes.
E 25 March 1944:
Arrives at Pusan, Korea. Undergoes repairs until May.
13 May 1944:
Reassigned to the Southern Expeditionary Fleet. Escorts convoys to Manila.
2 June 1944:
CH-23 and CH-56 depart Moji with kaibokan CD-14 and auxiliary subchasers CHa-90 and CHa-95 escorting MOTA-21 convoy (part 1) consisting of TAMA, AZUCHISAN, HAVRE (5467 GRT), NARUO (ex Panamanian ESTERO), CLYDE, HAMBURG, SEKIHO, TATSUAKI, SHINSHO, KINE, YAGI, IKOMASAN, TAIAN, TSUYAMA MARUs, SHINSEI MARU No.5, KOTO MARU No. 2 GO and seven unidentified merchant ships.
7 June 1944:
At 0900, an enemy submarine is sighted at 28-18N, 123-03E
9 June 1944:
At 0900, an enemy submarine is sighted at 24-50N, 120-30E
10 June 1944:
Arrives at Takao. Later that day, CH-23 departs Takao with kaibokan CD-14 escorting convoy MOTA-21 (part 2) consisting of HAVRE (5467 GRT), NARUO, CLYDE, HAMBURG, SEKIHO, TATSUAKI, SHINSHO, TSUYAMA, IKOMASAN, TAIAN, YAMAHAGI MARUs, SHINSEI MARU No.5 and one unidentified merchant ship. Initially the convoy is also escorted by the auxiliary submarine chasers KYO MARU No. 2 and TERUKAZE MARU.
13 June 1944:
Arrives at Manila.
27 June 1944:
Departs Manila with minelayer YAEYAMA escorting convoy H-30 consisting of HAVRE, CLYDE, SHINSHO, NARUO (ex ESTERO), TATSUAKI (TATSUSHO)and HAMBURG MARUs and SHINSEI MARU No. 5 and one unidentified merchant ship.
29 June 1944:
At 1130 arrives at Cebu.
30 June 1944:
At 0629 departs Cebu.
5 July 1944:
At 1615 arrives at Kau.
7 July 1944:
At 1300 departs Kau with minelayer YAEYAMA escorting M-26 convoy possibly consisting of HAMBURG, NARUO (ex Panamanian ESTERO), CLYDE, CHINKAI MARUs and SHINSEI MARU No. 5.
17 July 1944:
At 1740 theb M-26 convoy arrives. CH-23 had apparently detached.
19 July 1944:
CH-23 departs Manila with CH-31, CH-32, auxiliary submarine chaser CHa-24 and patrol boat PB-105 escorting convoy H-32 consisting of MIKASA, TAIYU, MIHARA, YAMABUKI, FUSAN, SAIHO, KYOKUZAN, KEIAN, NASUSAN and SHOHO MARUs.
21 July 1944:
At 1200 arrives at Cebu.
23 July 1944:
At 1830 departs Cebu with ASAHISAN MARU as additional convoy member (possibly patrol boat PB-105 only joins at this point, or may have joined between Manila and Cebu).
28 July 1944:
At 1440 arrives at Bitoeng, Halmahera Island.
1 August 1944:
Reassigned directly to the Combined Fleet and attached to SubChasDiv 21. Escorts convoys between Takao, Formosa, Shanghai, China, the Philippines and Japan.
16 October 1944:
Imari Bay. CH-23 joins the escort of convoy MOMA-05 consisting of DAIHAKU, KOMEI, TENSHO, DAISHO, TATSUURA, TAIYO, ESASHI, DORYO, PACIFIC, AOKI, TAIZAN (ex British ST QUENTIN), SAIHO and SUGIYAMA MARUs escorted by kaibokan KASADO and CH-17, CH-18 and CH-28. At 1820, the convoy departs.
21 October 1944:
At 1600, arrives at Takao. KASADO is detached.
23 October 1944:
At 0900, departs Takao and shelters in a bay on S Formosa, sailing at 2300.
24 October 1944:
At 1830, arrives at Sabtang Island anchorage.
25 October 1944:
At 0400, departs Sabtang Island.
26 October 1944:
At 0403, DAISHO MARU is torpedoed and sunk by LtCdr (later Rear Admiral) Maurice H. Rindskopf's (USNA ’38) USS DRUM (SS-228) at 19-30N, 120-44E. She takes down about 1600 men, most of whom belonged to the 57th Independent Brigade and 10th Maritime Advance Battalion. At 0655, Rindskopf also torpedoes DAIHAKU MARU carrying 3150 troops of 75th Mixed Brigade, 150 horses, 35 boats and 60 military dogs at 19-07N, 120-42E . The forepart sinks, although the aft part remains afloat and is successfully beached in Lapoc Bay. 1557 soldiers and three crewmen are KIA.
W of Dalupiri Island. At 0710, TAIYO MARU is torpedoed by LtCdr Richard W. Peterson's (USNA ’31) USS ICEFISH (SS-367) and sinks at 19-04N, 120-36E. A cargo of gasoline she is carrying for "kaiten" human-torpedoes ignites and sends flames hundreds of feet into the air. About 2200 troops on board together with 17 gunners and 13 crewmen are killed, and 22 landing craft, 26 horses and 21 motor vehicles are lost.
28 October 1944:
At 1230, anchors in Lapoc Bay.
29 October 1944:
At 0700, departs Lapoc Bay. At 1600. arrives at N San Fernando.
30 October 1944:
At 0700, departs N San Fernando. At 1600. arrives at Santa Cruz.
31 October 1944:
At 0500, departs Santa Cruz. At 0950, KOMEI MARU is torpedoed and sunk by LtCdr (later Captain) Enrique D. Haskins' (USNA ’33) USS GUITARRO (SS-363) at 15-18N, 119-50E. The ship was loaded with 3500 M3 of goods and 775 troops and 346 troops; three armed escort and 10 of the crew are killed. A few minutes later, at 1010, PACIFIC MARU is also torpedoed and sunk by GUITARRO at 15-15N, 119-56E. At the time the ship is carrying 300 Naval landing troops and war supplies. 24 soldiers, 27 gunners and 23 crewmen are killed.
5 November 1944:
CH-23 departs Manila with subchasers CH-17, CH-15, CH-37, CH-38 and kaibokan CD-18 and CD-26 escorting convoy MATA-31 consisting of TATSUHARU MARU and four unidentified merchant ships.
6 November 1944:
At 1055, an enemy submarine is sighted at 16-11N 109-06E.
11 November 1944:
At 0400, arrives at Manila.
15 November 1944:
Arrives at Takao.
10 January 1945:
CH-23, CH-17 and CH-38 depart Takao escorting convoy TAMO-36 consisting of YUKIKAWA MARU and one unidentified merchant ship.
14 January 1945:
Off San Fernando, Luzon. CH-23 is damaged by USAAF aircraft.
19 January 1945:
Arrives at Moji.
Escorts convoys to Shanghai.
15 August 1945:
Tsingtao, China. The crew of CH-23 receive notice of the termination of hostilities with the Allied Powers.
15 October 1945:
Removed from the Navy List.
10 December 1945:
Assigned to the Allied Repatriation Service and designated a special cargo ship.
Special thanks to Mr. Gilbert Casse of France for general assistance and to to Hans Mcilveen of the Netherlands for info on FRUMEL intercepts.
Allied signals (partial decrypt) and Japanese records both confirm CH-23 was a participant in this convoy.
-Bob Hackett, Sander Kingsepp and Peter Cundall.
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