(KOSHU MARU, prewar)
Tabular Record of Movement
©-2017 Bob Hackett
Kobe. Laid down at Kawasaki Shipyard as Yard No. 317, a 2,812-ton cargo ship.
28 November 1910:
Launched and named DAIUN MARU.
Sold to Takezaburo Hayashi (Osaka), renamed DAIUN MARU No. 3.
Sold to Osaka merchant ship, renamed KOSHU MARU.
28 November 1932:
Sold to Kai Green (Kyoto and Fuchu).
3 January 1943:
KOSHU MARU departs Saeki in No. 8 Military Movement's convoy "S" also consisting of ASAKA, HOKO, IKOMA, IWATE and NISHIYAMA (SEIZAN) MARUs escorted by patrol boat PB-31 and cable layer TSURUSHIMA.
E 4 January 1943:
The escorts are detached at 29N.
1 April 1943:
At 1300, KOSHU MARU departs Rabaul in a convoy also consisting of IJA transports ADEN MARU, IJN cargo ship KIKUKAWA MARU, IJN netlayer (B-AN) KYOSEI MARU and IJN cargo ship HEIWA MARU (B-AK) escorted by minesweeper W-22.
3 April 1943:
At 0800, arrives at Shortlands, Solomons and departs later in the day for Buin, Bougainville. Unloads some damaged equipment.
5 April 1943:
Unloads some damaged equipment.
8 April 1943:
At 1500, KOSHU MARU departs Buin in convoy with KIKUKAWA MARU.
10 April 1943:
At 0610, arrives at Rabaul.
10 May 1943:
At 0500, KOSHU MARU arrives at Shortland. At 1500, departs in a convoy also consisting of KASHI, SHINYU, SANWA MARUs and NISSEN MARU No. 5 escorted by minesweepers W-15 and W-22.
12 May 1943:
At 0800 arrives at Rabaul.
18 July 1943:
Buin, Bougainville, Solomons. USN VB-11 and USMC VMSB-132 "Dauntless" SBD dive-bombers and USN VT-11 and VT-21 "Avenger" TBF torpedo-bombers escorted by USMC VMF 122, VMF 211 and VMF 221 F4U "Corsair" fighters and USAAF B-24 "Liberator" heavy bombers escorted by USAAF P-39 "Airacobra" and P-40 "Warhawk" fighters and RNZAF P-40s attack shipping in the Buin-Kahili area. They sink destroyer HATSUYUKI and damage destroyers HATSUKAZE and YUNAGI and minesweeper W-15.
Later, W-22 tows W-15 to Keravia Bay, Rabaul. They share a convoy with KOSHU MARU and SUMIYOSHI MARU and depart at 1500 escorted by submarine chaser CH-12.
20 July 1943:
At 0930, the convoy and W-15 and W-22 arrive at Rabaul.
24 September 1943:
Requisitioned by the Imperial Army (IJA) and alloted IJA No. 517. 
Sold to Osaka merchant ship.
15 November 1944:
At 1600, KOSHU MARU departs Moji for Miri, Borneo in convoy MI-27 also consisting of AWAKAWA, CHINKAI, EDOGAWA, ENKEI, KYOKUUN, MATSUURA, OSAKASAN, SEISHO, and SHOHO MARUs escorted by kaibokan CD-61, CD-134, minesweeper W-101 and auxiliary subchasers CHa-156 and CHa-157. The convoy detours along the Korean coast to avoid American submarines. Immediately after departing ENKEI MARU drops out with rudder problems.
16 November 1944:
Tanker KYOKUUN MARU suffers engine problems and drops out.
17 November 1944:
Yellow Sea. Off Cheju Island. The convoy encounters a three-submarine wolf pack.
At 2205, LtCdr Edward E. Shelby's USS SUNFISH (SS-281) torpedoes and damages EDOGAWA MARU. About 2207, SUNFISH torpedoes and damages SEISHO MARU. Minesweeper W-101 attempts to assist. At 2340, LtCdr Robert H. Caldwell's USS PETO (SS-265) torpedoes and sinks OSAKASAN MARU at 33-30N, 124-30E.
18 November 1944:
At 0130, a gun battle erupts between a surfaced submarine and SEISHO MARU. At 0317, Selby's SUNFISH torpedoes and sinks damaged SEISHO MARU. At about the same time, Selby torpedoes EDOGAWA MARU again and she sinks. The rest of the convoy heads towards Shanghai for shelter. At about 0430, PETO torpedoes CHINKAI MARU carrying troops and ammunition. She sinks at 33-35N, 124-34E
At 1603, USN codebreakers at Fleet Radio Unit, Melbourne, Australia (FRUMEL) intercept and decode a message from W-101 that reads "Have the following survivors on board: 14 from OSAKASAN MARU, 36 from CHINKAI MARU, 186 from EDOGAWA MARU, 70 from SEISHO MARU. Expect to arrive at Raffles Island (30-42N, 122-26E) at 1200 on 19th. Allied submarine responsible attacked with unknown results."
23 November 1944:
CD-61 joins the convoy. The convoy splits into two sections, one heads for Singapore via Mako and the other for Luzon via Takao.
26 November 1944:
The remaining ships arrive at Takao.
13 March 1945:
At 2200, KOSHU MARU departs Kagoshima, Kyushu for Naha, Okinawa in convoy KANA-304 also consisting of KAIJO and SOKA MARUs and TSUKUSHI MARU No. 3 escorted by kaibokan CD-68, torpedo boat TOMOZURU, auxiliary minesweepers SEKI and CHITOSE MARUs and SHONAN MARU No. 16. Soon after leaving port, the convoy changes course for Koniya, Amami O-Shima because of Allied air activity in the Ryukyus.
16 March 1945:
At 2200, KANA-304 departs Amami O-Shima for Naha.
18 March 1945:
At about 1700, Cdr David R. Connole’s USS TRIGGER (SS-237) attacks the convoy from the port side. Connole torpedoes and sinks TSUKUSHI MARU No. 3.
20 March 1945:
At 1300, KANA-304 arrives at Shushan anchorage, E of Shanghai.
22 March 1945:
At 1700, KANA-304 departs Shushan for Naha.
23 March 1945:
At midnight, KANA-304 changes course north towards Amami O-Shima.
24 March 1945:
East China Sea. At 0830, two B-24 (possibly USN PB4Ys) “Liberator” heavy bombers attack KANA-304 and sink auxiliary minesweeper SEKI MARU off Tokara Gunto at 29-12N, 125-13E.
200 miles NW of Okinawa, near Amami O-Shima. Carrier planes from TG 58.1’s USS BENNINGTON (CV-20), USS HORNET (CV-12), USS BELLEAU WOOD (CVL-24) and USS SAN JACINTO (CVL-30) attack KANA-304 and sink cargo ships KOSHU MARU at 30-25N, 126-55E, SOKA and KAIJO MARUs at 28-25N, 124-32E and CD-68 at 30N, 126-36E and torpedo boat TOMOZURU, auxiliary minesweepers CHITOSE and SEKI MARUs and SHONAN MARU No. 16.
 The IJA probably requisitioned KOSHU MARU with same number during an earlier period; however, dates are unknown.
Thanks go to Erich Muehlthaler of Germany.
Back to IJA Transports