Japanese Auxiliary Netlayers

KYUSETSUMOKAN!

HOKAKUMOTEI!

PICTURE WANTED

IJN KOTOBUKI MARU No 5:
Tabular Record of Movement

© 2023 Gilbert Casse, Berend van der Wal and Peter Cundall

1 November 1938:
Innoshima. Laid down by Urabe Zosen Tekkosho G.K. as a 720-tons cargo ship for Sadaichi Fujioka.
22 April 1939:
Launched and named KOTOBUKI MARU No. 5.
15 July 1939:
Completed and registered at Osaka. Her Gross Registered tonnage (GRT) and Net Registered Tonnage (NRT) respectively are 720-tons and 396-tons. Her call sign is JCKN. [1]
13 September 1939:
Navy (Resv) Miyagawa Tokujiro is appointed CO.
15 September 1939:
Requisitioned by the IJN.
1940:
Departs Haikow (Haikou), Hainan Island, China for southern Chinese waters.
10 December 1940:
Arrives at Kirun, Formosa (now Keelung, Taiwan).
25 December 1940:
Uraga. Registered as an auxiliary netlayer attached to the Yokosuka Naval District under internal instruction No. 1018.
Navy (Resv) Lt(jg) Tonegi Hajime is appointed CO. Conversion to military duty begins at Uraga Senkyo K.K. shipyard.
14 January 1941:
Conversion to military duty is completed.
15 January 1941:
Attached to 56th SC Division under Internal order No. 29. Tactically assigned to Vice Admiral (later Admiral) Takasu Shiro’s (35) Fourth Fleet, 4th Base Force, 56th SC Division.
8 February 1941:
Departs Yokosuka for the South Seas (Japanese mandated Islands).
14 February 1941:
Rated as No. 56-1 netlayer ship.
2 June 1941:
Navy (Resv) Lt(jg) Tonegi Hajime is confirmed as CO.
1 September 1941:
Attached to 4th Base Force, 56th SC Division under Fourth Fleet order No. 228.
15 October 1941:
Attached to 56th SC Division under internal order No. 1251.
December 1941:
Attached to Truk, Central Carolines Defense Force, Sea Surface Defense Unit.
4 December 1941:
Heads towards Ponape, Carolines.
2 January 1942:
Departs Ponape.
5 January 1942:
Arrives at Truk and enters drydock. Rated as an R Invasion Unit under South Seas Unit Command No. 7.
6 January 1942:
Rated as a Main Corps Patrol Unit under R Invasion Unit order No. 1.
10 January 1942:
Undocked.
17 January 1942: Operation "R" The Invasions of Rabaul, New Britain, Bismarck Islands, Australia (now Papua, New Guinea) and Kavieng, New Ireland, Bismarck Islands, Australia (Now Papua, New Guinea):
Departs Truk.
22 January 1942:
Arrives at Outer Rabaul Bay.
23 January 1942:
At 0140, enters Rabaul harbor. Seizes a ship. Rated as a main patrol unit under R Invasion Unit order No. 15.
24 January 1942:
Supplied with 50-tons of coal by auxiliary gunboat NIKKAI MARU.
25 January 1942:
Supplied with 20-tons of water by minelayer OKINOSHIMA.
26 January 1942:
Mothership in charge is determined under R Invasion Unit order No. 19:
- For 14th Minesweeping Division: minelayer OKINOSHIMA.
- For 56th SC Division: minelayer TSUGARU.
31 January 1942:
Supplied with water by fleet oiler IRO.
1 February 1942:
Attached to Vice Admiral (later Admiral) Inoue Shigeyoshi’s (37) Fourth Fleet, 8th Special Base Force, 56th SC Division under Fourth Fleet order No. 409. Attached to R Invasion Corps Base Area, Transport Maritime Corps, Third Unit.
2 February 1942:
Departs Rabaul on patrol in areas No. 4 and No. 5.
4 February 1942:
Arrives at Rabaul.
6 February 1942:
Departs Rabaul on patrol in areas No. 1 and No. 3.
8 February 1942:
Arrives at Rabaul.
10 February 1942:
Departs Rabaul on patrol in areas No. 2 and No. 3.
12 February 1942:
Arrives at Rabaul.
14 February 1942:
Departs Rabaul on patrol in area No. 1.
15 February 1942:
Arrives at Rabaul.
16 February 1942:
Departs Rabaul on patrol in area No. 1.
18 February 1942:
Arrives at Rabaul.
19 February 1942:
Departs Rabaul on patrol in area No. 1.
20 February 1942:
Arrives at Rabaul, departs there and returns to base later this day.
March 1942:
Attached to the Marine Corps under Rabaul Defense area secret order No. 1.
11 April 1942:
Departs Rabaul.
12 April 1942:
Arrives at Rabaul. Attached to the Base Transport, Marine Corps under Rabaul Defense area secret order No. 7.
16 April 1942:
Departs Rabaul.
17 April 1942:
Arrives at Rabaul.
20 April 1942:
Departs Rabaul.
21 April 1942:
Arrives at Rabaul.
22 April 1942:
Attached to the Marine Corps under Rabaul Defense area secret order No. 10.
25 April 1942:
Departs Rabaul.
26 April 1942:
Arrives at Rabaul.
3 May 1942:
At 0925, outside Rabaul harbor at 80° and 2,300m of ‘Sister Mountain’ drops six depth charges.
11 May 1942:
0900 ~ 1500: Lies alongside auxiliary munitions ship KOTOKU MARU and is supplied with coal.
30 May 1942:
Supplied with boiler water by auxiliary gunboat SEIKAI MARU.
4 June 1942:
Departs Rabaul.
5 June 1942:
Arrives at Rabaul.
6 June 1942:
Departs Rabaul and returns there later that day.
8 June 1942:
Departs Rabaul.
9 June 1942:
Arrives at Rabaul.
12 June 1942:
Departs Rabaul.
14 June 1942:
Arrives at Rabaul.
17 June 1942:
Departs Rabaul.
18 June 1942:
Arrives at Rabaul.
23 June 1942:
Departs Rabaul.
24 June 1942:
Arrives at Rabaul.
25 June 1942:
Departs Rabaul.
26 June 1942:
Arrives at Rabaul.
28 June 1942:
Departs Rabaul.
29 June 1942:
Arrives at Rabaul.
30 June 1942:
Navy (Resv) Lt(jg) Hirano Bunichi is appointed CO. Departs Rabaul that same day.
1 July 1942:
Arrives at Rabaul.
4 July 1942:
Departs Rabaul.
5 July 1942:
Arrives at Rabaul.
8 July 1942:
Departs Rabaul.
9 July 1942:
Arrives at Rabaul.
11 July 1942:
Departs Rabaul.
12 July 1942:
Arrives at Rabaul.
15 July 1942:
Departs Rabaul.
16 July 1942:
Arrives at Rabaul.
18 July 1942:
Departs Rabaul.
19 July 1942:
Arrives at Rabaul.
20 July 1942:
Departs Rabaul.
21 July 1942:
Arrives at Rabaul.
24 July 1942:
Departs Rabaul.
25 July 1942:
Arrives at Rabaul.
28 July 1942:
Departs Rabaul.
29 July 1942:
Arrives at Rabaul.
30 July 1942:
Departs Rabaul and returns to anchorage later this day.
31 July 1942:
Departs Rabaul.
1 August 1942:
Arrives at Rabaul. Navy (Resv) Lt(jg) Hirano Bunichi is confirmed as CO.
3 August 1942:
Departs Rabaul.
4 August 1942:
Arrives at Rabaul.
6 August 1942:
Departs Rabaul.
7 August 1942:
Arrives at Rabaul.
10 August 1942:
Departs Rabaul.
11 August 1942:
Arrives at Rabaul.
14 August 1942:
Departs Rabaul for Shortlands, British Solomon Islands Protectorate (now Solomon Islands).
20 August 1942:
Arrives at Rabaul.
25 August 1942:
Departs Rabaul.
26 August 1942:
Arrives at Rabaul.
28 August 1942:
Departs Rabaul.
29 August 1942:
Arrives at Rabaul.
31 August 1942:
Departs Rabaul.
E 1 September 1942:
Arrives at Rabaul.
28 September 1942:
Attached to RR Maritime Defense Force under Rabaul Defense area secret order No. 35.
E 30 September 1942:
Departs Rabaul.
3 October 1942:
Arrives at Rabaul.
4 October 1942:
Departs Rabaul.
5 October 1942:
Arrives at Rabaul.
6 October 1942:
Departs Rabaul.
8 October 1942:
Arrives at Rabaul.
10 October 1942:
Departs Rabaul.
12 October 1942:
Arrives at Rabaul. Departs there later that day.
13 October 1942:
Arrives at Rabaul.
14 October 1942:
Departs Rabaul.
15 October 1942:
Arrives at Rabaul.
16 October 1942:
Departs Rabaul.
17 October 1942:
Arrives at Rabaul.
18 October 1942:
Departs Rabaul.
19 October 1942:
Arrives at Rabaul.
20 October 1942:
Departs Rabaul.
21 October 1942:
Arrives at Rabaul.
24 October 1942:
Departs Rabaul.
25 October 1942:
Arrives at Rabaul. Sinks with unknown casualties after being bombed by a USAAF 5th Air Force Boeing ‘Flying Fortress’ B-17 NW Rabaul on N shore near Korere Bay. Initially sank with the bow above water but later slipped underwater.
30 November 1942:
Removed from the Navy’s list under order No. 2198.
C 1960’s:
Wreck found by local Rabaul Diver George Tyers and given the nickname “George’s Wreck”. The wreck sits on a slope with the funnel collapsed to starboard. The netlaying rollers attached to either side of the bow remain a prominent feature.

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.
Thanks go to Gengoro S. Toda of Japan.

- Gilbert Casse, Berend van der Wal and Peter Cundall.

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