Japanese icebreaker Ōtomari

History
Ōtomari in November 1921 at Kōbe
Japan
Name:	Ōtomari
Namesake:	Port of Ōtomari
Ordered:	1920 Fiscal year under the Eight-eight fleet plan
Builder:	Kawasaki Shipbuilding Corporation
Laid down:	24 June 1921
Launched:	3 October 1921
Completed:	7 November 1921
Decommissioned:	15 September 1945
Fate:	Scrapped between October 1949–March 1950.
General characteristics as built
Type:	Icebreaker
Displacement:	2,330 long tons (2,367 t) standard
Length:	60.96 m (200.0 ft) pp
Beam:	15.24 m (50 ft 0 in)
Draught:	5.55 m (18 ft 3 in)
Propulsion:	2 × triple expansion reciprocating engines, 5 × scotch boilers 2 shafts, 4,000 shp
Speed:	13 knots (15 mph; 24 km/h)
Range:	4,000 nmi (7,400 km) at 14 knots
Endurance:	Fuel: 500 tons coal
Complement:	101
Armament:	as built 1 × Armstrong 3 in L/40 gun In the Pacific War 1 × Armstrong 3 in L/40 gun 2 × Type 96 25 mm AA guns 6 × Type 93 13 mm AA guns some depth charges

The Ōtomari (大泊)^[1] was an icebreaker of the Imperial Japanese Navy (IJN) serving during the 1920s through World War II, the only ship of her class. She was an only icebreaker as warship in the IJN.

Background

Russian icebreaker Dobrynya Nikitich

Ōtomari was planned as one of the Kamoi-class oilers under the Eight-eight fleet plan at first. However, Nikolayevsk Incident changed her future. IJN was not able to dispatch their warship to Nikolayevsk which froze, because they did not have an icebreaker. All Japanese civilians were killed by terrorists in this incident. Japan was afraid that this dire disaster could occur once again, because the Russian Civil War continued in this time. As a result, the budget for the vessels was rearranged: only the lead ship of Kamoi-class oiler was built, plus three oilers of Ondo-class, one food supply ship (Mamiya), and one icebreaker (Ōtomari).
As Japan had no prior experience in building icebreakers, the IJN began by observing icebreaker architectures of neighboring countries, and decided to base Ōtomari on the Russian icebreaker Dobrynya Nikitich. The IJN hurried the construction of Otomari, because they wanted her by the Winter of 1921, and she was launched less than four months after her keel was laid down.
She was assigned to Ōminato Guard District and took northern patrol duties, and continued active service throughout her life.

Because Ōtomari was small and aging by World War II, the IJN planned her succeeding ship Esan (恵山, Project Number J23, 6,800 tons standard) under the Kai-Maru 5 program in 1942; however Esan was canceled in 1943.

Service

Ōtomari acted in Sakhalin, Kuril Islands and Sea of Okhotsk between all time except maintenance. In July 1945, she sailed to Yokosuka Naval Arsenal for maintenance. However, she was not able to take maintenance because Japan had surrendered. Japan was going to employ her as repatriation transport, however, it was given up, because her boiler was worn out. She was scrapped in March 1950.

References

↑ 30 May 1921, Notice No. 104, Named one auxiliary vessel., Minister's Secretariat, Ministry of the Navy.

Bibliography

Ships of the World special issue Vol.47 Auxiliary Vessels of the Imperial Japanese Navy, Kaijinsha, (Japan), March 1997
The Maru Special, Japanese Naval Vessels No.34, "Japanese Auxiliary vessels", Ushio Shobō (Japan), December 1979
The Maru Special, Japanese Naval Operations in WWII No.111, "Imperial Japanese Naval Vessels in postwar", Ushio Shobō (Japan), May 1986
Senshi Sōsho Vol.31, Naval armaments and war preparation (1), "Until November 1941", Asagumo Simbun (Japan), November 1969
"Rekishi Gunzō". History of Pacific War Vol.37, "Support vessels of the Imperial Japanese Army and Navy", Gakken (Japan), June 2002, ISBN 4-05-602780-3

Japanese auxiliary ship classes of World War II

Colliers and oilers	Notoro Ondo Sunosaki Ashizuri Kazahaya^S Hayasui^S Hario^S Muroto Teiyō Maru^S Ōse (ex-Dutch tanker Genota)^SC

Food supply ships	Mamiya^S Nosaki^S Kinesaki Irako^S Kurasaki^SC

Landing ships	No.1 No.101 Shinshū Maru^S (Army) SS (Army)

Armed merchant cruisers	Aikoku Maru^S Kongō Maru^S Noshiro Maru^S

Minelayers and cable layer	Tokiwa^SC Itsukushima^S Yaeyama^S Okinoshima^S Tsugaru^S Minoo^SC Shirataka^S Hatsutaka Tsubame Natsushima (1933) Sokuten (1938) Hirashima Ajiro^S Kamishima Hashima Sokuten (1913) Aux. No.1 Aux. No.101 (ex-HMS Barlight)^SC

Minesweepers	No.1 (1923) No.5 (1928) No.13 No.17 No.7 (1938) No.19 No.101 (ex-HMS Taitam and HMS Waglan)^C Aux. No.1 Aux. No.101 (ex-HNLMS DEFG-class) Aux. No.104 (ex-HNLMS DEFG-class)

Patrol boats	No.1^C No.31^C No.46^SC No.101 (ex-HMS Thracian)^SC No.102 (ex-USS Stewart)^SC No.103 (ex-USS Finch)^SC No.104 (ex-Dutch East Indies Valk and Arend)^C No.105 (ex-Philippine customs Arayat)^SC No.106 (ex-HNLMS Banckert (1929))^SCI No.107 (ex-USS Genesee)^SC No.109 (ex-Dutch East Indies Fazant)^SC Aux. No.1

Repair ships	Asahi^SC Akashi^S Hayase (ex-Chinese passenger Chin Kiang)^SC Hitonose (ex-ROCN Min Sheng)^SC

Seaplane tenders	Notoro Kamoi^SC Chitose Mizuho^S Nisshin^S Akitsushima^S Kamikawa Maru

Submarine chasers	No.1 No.3^S No.4 No.13 No.28 No.60 Aux. No.1 Aux. No.101 (ex-HNLMS Tjerimai)^SC Aux. No.102 (ex-HNLMS Ardjoeno class)^C Aux. No.103 (ex-HNLMS B1 class)^C Aux. No.111 (ex-HNLMS P13 or P14)^SC Aux. No.112 (ex-HNLMS A class)^C Aux. No.117 (ex-HNLMS Bantam)^C Aux. No.251 Aux. No.253^S

Submarine tenders	Komahashi^SC Jingei Taigei^S

Survey ships	Tsukushi^S Katsuriki^SC Hakusa (ex-China customs Fu Hsing)^SC

Target ships	Settsu^SC Yakaze^SC Hakachi^S Ōhama^S

Training ships	Fuji^SC Shikishima^SC Asama^SC Azuma^SC Kasuga^SC Atada (ex-ROCN Yat Sen)^SC

Others	Sōya (freighter)^SC Kashino (turret transporter)^S Ōtomari (icebreaker)^S Tategami (salvage tug) Kasashima (salvage tug) Miura (salvage tug) Kaiyō No.1 (oceanographic research ship) Asuka (traffic ship, ex-ROCN Yung Chien)^SC

S Single ship of class C Converted to ship type I Incomplete until the end of war

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