ZATSUYOSEN!

(Ryotoku Maru prewar)

IJN RYOTOKU MARU:
Tabular Record of Movement

© 2014 Gilbert Casse, Bob Hackett and Peter Cundall

Revision 1


30 October 1937:
Tama. Laid down by Tama Zosensho K.K. shipyard for Oya Shoji K.K. as a 3,527-tons cargo ship.

17 March 1938:
Launched and named RYOTOKU MARU.

7 May 1938:
Completed and registered in Osaka. Her Gross Registered Tonnage (GRT) and Net Registered Tonnage (NRT) respectively are 3,527-tons and 1,993-tons.

[1] 1940:
Her GRT and NRT are respectively changed to 3,483-tons and 1,980-tons.

[1] 19 March 1941:
Requisitioned by the IJN as general requisitioned transport (Ippan Choyosen) attached to the Yokosuka Naval District. Departs Shibaura, Tokyo and arrives at Yokosuka later that same day.

March 1941:
Departs Yokosuka and arrives at Fais, Eastern Carolines.

1 May 1941:
Released to her owners.

25 August 1941:
Requisitioned again by the IJN.

26 August 1941:
Starts conversion to military duty at Tama Zosensho K.K. shipyard.

5 September 1941:
Registered in the IJN as an auxiliary gunboat attached to the Sasebo Naval District with Sasebo as homeport under instruction No. 1025. Assigned to minelaying duty under instruction No. 1026. IJN Captain Kiyomiya Yoshitaka (33) is appointed CO.

5 October 1941:
The conversion is completed.

December 1941:
Tactically assigned to Vice Admiral Sakamoto Ikuta’s (36) Chinkai Guard District.

6 December 1941:
Departs Chinkai, Chosen (now Jinhae, South Korea).

7 December 1941:
Arrives back at Chinkai. Tactically assigned that same day to Tsushima Strait Defense Forces under Chinkai Guard District secret instruction No. 12.

9 December 1941:
Departs Chinkai and arrives at Busan (Fuzan), Chosen (now Pusan, South Korea) later in the day.

18 December 1941:
Departs Busan and arrives at Chinkai later that day.

23 December 1941:
Departs Chinkai.

25 December 1941:
Arrives back at Chinkai.

29 December 1941:
Departs Chinkai and returns to port later in the day.

10 January 1942:
Departs Chinkai and engages in training exercise.

11 January 1942:
Arrives back at Chinkai.

24 January 1942:
Departs Chinkai, calls at Unijima; departs there and arrives off Hitakatsu, Nagasaki Prefecture later that day.

25 January 1942:
Off Miura Wan (Bay). Assists auxiliary subchaser TSURAN MARU, in cargo inspection before releasing Soviet merchant ship ANADIR.

26 January 1942:
Arrives at Kechi, Nagasaki Prefecture. Departs there and calls at Izuhara, Nagasaki Prefecture and Kanzaki, Hiroshima Prefecture.

27 January 1942:
Arrives at Wakamiya, Kyoto Prefecture. Departs there and calls at Gonoura, Iki Island.

28 January 1942:
Arrives at Chinkai.

6 February 1942:
Departs Chinkai. Operates with other ships and returns back to port later in the day.

20 February 1942:
IJN Reserve Lt. (Cdr. posthumously) Nagabuchi Torao is appointed CO.

2 March 1942:
Departs Chinkai.

3-4 March 1942:
Engages alone off Busan in training exercise.

5 March 1942:
Arrives back at Chinkai.

16 March 1942:
Departs Chinkai.

19 March 1942:
Arrives back at Chinkai.

25 March 1942:
Departs Chinkai and operates with other ships before returning to port later in the day.

26 March 1942:
Departs Chinkai and operates with other ships before returning to port later in the day.

8 April 1942:
Departs Chinkai on training mission.

9 April 1942:
Arrives back at Chinkai.

13 April 1942:
Departs Chinkai and engages in gunnery drill before returning to port later in the day.

15 April 1942:
Departs Chinkai and arrives at Busan later that day.

2 May 1942:
Departs Busan and arrives at Chinkai later that same day.

20 May 1942:
Departs Chinkai.

E 21 May ~ 5 June 1942:
Operates in northern waters and returns back to Chinkai.

June 1942:
Loads 37-tons of ammunition.

7 June 1942:
Departs Chinkai heading for Rashin, Chosen (now Rajin, North Korea).

9 June 1942:
Arrives back at Chinkai.

14 June 1942:
Departs Chinkai.

17 June 1942:
Arrives at Busan.

21 June 1942:
Departs Busan.

25 June 1942:
Arrives at Chinkai.

29 June 1942:
Departs Chinkai.

3 July 1942:
Arrives at Busan.

5 July 1942:
Departs Busan and arrives at Chinkai later in the day.

7 July 1942:
Departs Chinkai.

8 July 1942:
Arrives back at Chinkai.

9 July 1942:
Departs Chinkai on training mission.

10 July 1942:
Arrives at Busan.

11 July 1942:
Departs Busan.

12 July 1942:
Arrives back at Busan.

13 July 1942:
Departs Busan.

14 July 1942:
Arrives back at Busan.

15 July 1942:
Departs Busan.

16 July 1942:
Arrives back at Busan.

17 July 1942:
Departs Busan.

18 July 1942:
Arrives back at Busan.

19 July 1942:
Departs Busan and arrives at Chinkai later that day.

23 July 1942:
Departs Chinkai.

26 July 1942:
Arrives back at Chinkai.

1 August 1942:
Departs Chinkai.

3 August 1942:
Arrives at Busan. Departs later that day.

4 August 1942:
Arrives at Chinkai.

8 August 1942:
Departs Chinkai.

12 August 1942:
Arrives back at Chinkai.

15 August 1942:
Departs Chinkai and arrives at Busan later that same day.

16 August 1942:
Enters Chosen Heavy Industries K.K. Drydock for maintenance and repairs.

21 August 1942:
Undocked.

22 August 1942:
Departs Busan and arrives at Chinkai later in the day.

24 August 1942:
Departs Chinkai and arrives at Busan later that day.

25 August 1942:
Reserve Captain Nagabuchi is reassigned to the Yokosuka Naval District Office. RYOTOKU MARU is removed from the Navy’s list under instruction No. 1581. She is again registered that same day in the IJN as an auxiliary transport, (Otsu) category attached to the Sasebo Naval District with Sasebo as homeport under instruction No. 1582.

[2] 26 August 1942:
Departs Busan.

27 August 1942:
Arrives at Motoyama.

30 August 1942:
Departs Motoyama.

31 August 1942:
Arrives at Chinkai.

2 September 1942:
Officially rerated as auxiliary transport.

3 September 1942:
Departs Chinkai.

4 September 1942:
Arrives at Sasebo.

7 September 1942:
Scheduled to undergo conversion to auxiliary transport (Otsu) category at the Sasebo Naval Yard under Navy’s secret instruction No. 11261 .

[2] September 1942:
Begins scheduled conversion at the Sasebo Naval Yard.

12 September 1942:
Officially shifts category.

1 October 1942:
The conversion is completed. Departs Sasebo.

4 October 1942:
Arrives at Dairen, Manchuria (now Dalian, northern China).

8 October 1942:
Departs Dairen.

11 October 1942:
Arrives at Moji.

12 October 1942:
Departs Moji.

13 October 1942:
Arrives at Yoshiura near Kure.

15 October 1942:
Departs Yoshiura.

16 October 1942:
Arrives at Kobe.

19 October 1942:
Departs Kobe.

20 October 1942:
Arrives at Moji.

21 October 1942:
Departs Moji.

23 October 1942:
Arrives at Makishima, Fukui Prefecture.

24 October 1942:
Departs Makishima.

26 October 1942:
Arrives at Dairen.

28 October 1942:
Departs Dairen.

1 November 1942:
Arrives at Osaka.

4 November 1942:
Departs Osaka.

5 November 1942:
Arrives at Kure.

8 November 1942:
Departs Kure.

9 November 1942:
Arrives at Moji. Departs later that day.

12 November 1942:
Arrives at Dairen.

15 November 1942:
Departs Dairen.

19 November 1942:
Arrives at Kure.

24 November 1942:
Departs Kure.

25 November 1942:
Arrives at Moji. Departs later that same day.

30 November 1942:
Arrives at Dairen.

3 December 1942:
Departs Dairen.

7 December 1942:
Arrives at Sasebo.

11 December 1942:
Departs Sasebo.

12 December 1942:
Arrives at Kure.

17 December 1942:
Departs Kure.

18 December 1942:
Arrives at Wakamatsu, Fukuoka Prefecture.

20 December 1942:
Departs Wakamatsu.

21 December 1942:
Arrives at Kure.

23 December 1942:
Departs Kure.

24 December 1942:
Arrives at Osaka.

29 December 1942:
Departs Osaka.

31 December 1942:
Arrives at Moji. Departs at 1600 in convoy No. 110 also consisting of one unidentified merchant ship without surface escort. The convoy sails at 9.5 knots. RYOTOKU MARU carries a cargo of timber.

5 January 1943:
Arrives at Takao, Formosa (now Kaohsiung, Taiwan). The other ship has detached earlier for Kirun.

10 January 1943:
Departs Takao.

12 January 1943:
Arrives at Fangliao, Formosa.

13 January 1943:
Departs Fangliao.

14 January 1943:
Arrives at Kirun (now Keelung), Formosa.

20 January 1943:
Departs Kirun.

25 January 1943:
Arrives at Kobe.

26 January 1943:
Departs Kobe.

28 January 1943:
Arrives at Tokyo.

31 January 1943:
Departs Tokyo.

2 February 1943:
Arrives at Osaka.

8 February 1943:
Departs Osaka.

9 February 1943:
Arrives at Moji.

10 February 1943:
At 1630, departs Moji in convoy No. 126 also consisting of auxiliary transport KOSHIN MARU and three unidentified merchant ships without escort. At 1220, auxiliary transport KOSEI MARU (2,205 GRT) joins the convoy from Sasebo.

14 February 1943:
Anchors off An Ping.

15 February 1943:
At 0900, arrives at Takao.

19 February 1943:
Departs Takao.

21 February 1943:
Arrives at Kirun.

26 February 1943:
Departs Kirun.

3 March 1943:
Arrives at Osaka.

6 March 1943:
Departs Osaka and arrives at Aioi, Hyogo Prefecture later that day.

E 7 ~ 25 March 1943:
Undergoes repairs.

26 March 1943:
Departs Aioi.

27 March 1943:
Arrives at Moji. Departs later that same day.

28 March 1943:
Arrives at Tsukumi, Oita Prefecture, Kyushu.

2 April 1943:
Departs Tsukumi.

3 April 1943:
Arrives at Kobe. Departs there and arrives at Wakaura, Wakayama Prefecture later that day.

5 April 1943:
Departs Wakaura.

7 April 1943:
Arrives at Koura, Shimane Prefecture.

8 April 1943:
Departs Koura and arrives at Shibaura, Tokyo later that day. Departs later.

10 April 1943:
Departs Yawata in convoy No. 7415 also consisting of IJA transports GINYO, TAISHO (4,815 GRT) and RYUA MARUs, auxiliary transport SEIZAN MARU No. 2 and IJN requisitioned cargo ship (B-AK) HEIWA MARU escorted by subchaser CH-40.

13 April 1943:
Arrives at Tokyo Wan (Bay). Transfers later in the day to Shibaura.

14 April 1943:
Departs Shibaura and arrives at Yokosuka later that same day.

15 April 1943:
Departs Yokosuka in convoy No. 7415 also consisting of IJA transports GINYO, RYUA, TAISHO MARUs, auxiliary transport SEIZAN MARU No. 2 and an unidentified merchant ship escorted by subchaser CH-40.

17 April 1943:
Arrives at Osaka.

21 April 1943:
Departs Osaka.

22 April 1943:
Arrives at Moji.

24 April 1943:
Departs Moji in J convoy also consisting of six unidentified merchant ships with a single unidentified escort.

29 April 1943:
Arrives at Takao.

5 May 1943:
Departs Takao.

6 May 1943:
Arrives at Kirun.

10 May 1943:
Departs Kirun.

15 May 1943:
Arrives at Osaka.

19 May 1943:
Departs Osaka.

20 May 1943:
Arrives at Moji.

21 May 1943:
Departs Moji.

22 May 1943:
Arrives at Motoyama, Aichi Prefecture.

26 May 1943:
Departs Motoyama.

28 May 1943:
Arrives at Yoshiura, Kure.

2 June 1943:
Departs Yoshiura.

3 June 1943:
Arrives at Yobuko, Saga Prefecture, Kyushu.

4 June 1943:
Departs Yobuko and arrives at Miike, Fukuoka Prefecture later in the day.

7 June 1943:
Departs Miike and arrives at Arikawa Wan (Bay), Wakamatsu Island, Nagasaki Prefecture later that same day.

8 June 1943:
Departs Arikawa Wan.

9 June 1943:
Arrives at Kobe Wan.

10 June 1943:
Departs Kobe Wan.

11 June 1943:
Arrives at Osaka.

12 June 1943:
Departs Osaka.

13 June 1943:
Arrives at Moji.

14 June 1943:
Departs Moji.

18 June 1943:
Arrives at Chinnampo.

21 June 1943:
Departs Chinnampo.

26 June 1943:
Arrives at Osaka.

27 June ~ 4 July 1943:
Undergoes engine repair at Hitachi Zosen K.K. Shipyard.

5 July 1943:
Repairs are completed.

6 July 1943:
Departs Osaka and arrives at Kobe later in the day.

7 July 1943:
Departs Kobe.

8 July 1943:
Arrives at Nagoya.

9 July 1943:
Departs Nagoya.

10 July 1943:
Arrives at Yokosuka.

16 July 1943:
Departs Yokosuka.

17 July 1943:
Arrives at Toba, Mie Prefecture.

19 July 1943:
Departs Toba and arrives at Yokkaichi, Mie Prefecture later that same day.

22 July 1943:
Departs Yokkaichi and arrives at Nagoya later that day.

23 July 1943:
Departs Nagoya and arrives at Toba later in the day.

24 July 1943:
Departs Toba.

25 July 1943:
Arrives at Yokosuka.

27 July 1943:
Departs Yokosuka and arrives at Tokyo later that day.

31 July 1943:
Departs Yokosuka, calls at Yokohama and departs later that day.

4 August 1943:
Arrives at Otaru, Hokkaido.

5 August 1943:
Departs Otaru.

8 August 1943:
Arrives at Kataoka Wan, Shimushu-To, Kuriles (now Zaliv Kozyrevskogo, Ostrov Shumshu).

12 August 1943:
Departs Kataoka Wan and arrives at Suribachi Wan, Paramushiro-To, Kuriles later in the day.

20 August 1943:
Departs Suribachi Wan and arrives at Musashi Wan (now Zaliv Vasil’yeva), Paramushiro later that same day.

29 August 1943:
Departs Musashi Wan.

30 August 1943:
Arrives at Kataoka Wan. Departs later that day.

4 September 1943:
Arrives at Muroran, Hokkaido.

6 September 1943:
Departs Muroran.

9 September 1943:
Arrives at Yokohama.

11 September 1943:
Departs Yokohama and arrives at Yokosuka later in the day.

16 September 1943:
Departs Yokosuka.

20 September 1943:
Arrives at Chichi Jima, Ogasawara Gunto (Bonins).

21 September 1943:
Departs Chichi Jima for Saipan, Marianas in convoy No. 3916 also consisting of IJA transport YAMASHIRO MARU escorted by auxiliary minesweepers KEINAN MARU and FUMI MARU No. 2. The ship is bound for Truk then Rabaul.

23 September 1943:
About 135 nautical miles W Urracas (Farallon de Pajaros), northern Marianas. About 0800, LtCdr Albert H. Clark’s (USNA ’33) USS TROUT (SS-202) sights two ships and an escort. At 0830, the submarine fires a spread of three torpedoes at each of the merchant targets. RYOTOKU MARU is hit first in stern by two torpedoes. Unable to steer, the transport is disabled. At 0850, Clark attacks again and scores another hit on RYOTOKU MARU port amidships. At 1008, the auxiliary transport sinks stern first, at 20-45N, 142-10E with unknown casualties.

Meantime, Clark’s first attack also hits YAMASHIRO MARU carrying 151 passengers, 2,160-tons of general cargo and 150-tons of coal, with two torpedoes in her starboard engine room. The Army transport is set afire and abandoned by her crew. She sinks about 0838 with the loss of four crewmen and seven passengers.

1 December 1943:
Removed from the Navy’s list under instruction No. 2564.


Authors' Notes :
[1] NRT is a ship's cargo volume capacity expressed in "register tons", one of which equals to a volume of 100 cubic feet (2.83 m3). It is calculated by subtracting non-revenue-earning spaces i.e. spaces not available for carrying cargo, for example engine rooms, fuel tanks and crew quarters, from the ship's gross register tonnage (GRT). Net register tonnage (NRT) is not a measure of the weight of the ship or its cargo, and should not be confused with terms such as deadweight tonnage or displacement.

[2] There were two categories of Zatsuyosen. (Ko) category with an IJN Captain as supervisor aboard and (Otsu) category without.

Thanks go to Gengoro S. Toda of Japan. Thanks goes also to Matthew Jones for providing additional CO info.

Gilbert Casse, Bob Hackett and Peter Cundall


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