View source for Japanese submarine I-203

{{confuse|Japanese submarine Ha-203}}
{|{{Infobox ship begin}}
{{Infobox ship image
|Ship image=Japanese submarine I-203 1945.jpg
|Ship caption=''I-203'' in 17 December 1945
}}
{{Infobox ship career
|Hide header=
|Ship country=[[Empire of Japan]]
|Ship flag={{shipboxflag|Japan|naval}}
|Ship name=''I-203''
|Ship namesake=
|Ship ordered=
|Ship builder=[[Kure Naval Arsenal]], [[Kure, Hiroshima|Kure]],&nbsp;[[Japan]]
|Ship laid down=1 June 1944
|Ship launched=20 October 1944
|Ship completed=29 May 1945
|Ship commissioned=29 May 1945
|Ship decommissioned=
|Ship in service=
|Ship out of service=
|Ship struck=30 November 1945
|Ship fate=*Surrendered 2 September 1945
*Sunk as target 21 May 1946
}}
{{Infobox ship characteristics
|Hide header=
|Header caption=
|Ship class={{sclass|I-201|submarine}}
|Ship displacement=*{{Convert|1291|LT|t|0|disp=flip}} surfaced
*{{Convert|1450|LT|t|0|disp=flip}} submerged
|Ship length={{convert|79|m|ftin|abbr=on}}
|Ship beam={{convert|5.8|m|ftin|abbr=on}}
|Ship draft={{convert|5.4|m|ftin|abbr=on}}
|Ship power=*{{convert|2750|bhp|lk=in|abbr=on}} (diesels)
*{{convert|5000|hp|abbr=on}} (electric motors)
|Ship propulsion=*[[Diesel-electric]]
*2 × [[diesel engine]]s
*2 × [[electric motor]]s
|Ship speed=*{{convert|15.8|kn|lk=in}} surfaced
*{{convert|19|kn}} submerged
|Ship range=*{{convert|5800|nmi|abbr=on|lk=in}} at {{convert|14|kn}} surfaced
*{{convert|135|nmi|abbr=on}} at {{convert|3|kn}} submerged
|Ship endurance=
|Ship test depth={{convert|110|m|ft|abbr=on}}
|Ship complement=31
|Ship armament=*4 × bow {{convert|533|mm|in|0|abbr=on}} [[torpedo tube]]s
*2 × single [[Type 96 25&nbsp;mm AT/AA Gun|Type 96 {{convert|25|mm|in|abbr=on}}]] [[anti-aircraft gun]]s
}}
|}

The '''Japanese submarine ''I-203''''' was an  [[I-201-class submarine|''I-201''-class]] high-speed [[submarine]] built for the [[Imperial Japanese Navy]] during [[World War II]]. She was commissioned in May 1945, and the war ended before she could carry out an operational patrol. She surrendered to the [[United States Navy]] in 1945 and was sunk as a target in 1946.

==Design and description==
The ''I-201''-class submarines were derived from the experimental high-speed ''[[Submarine No.71]]''. They [[Displacement (ship)|displaced]] {{Convert|1291|LT|t|0|disp=flip}} surfaced and {{Convert|1450|LT|t|0|disp=flip}} submerged. The submarines were {{convert|79|m|ftin|sp=us}} long, had a [[beam (nautical)|beam]] of {{convert|5.8|m|ftin|sp=us}} and a [[draft (hull)|draft]] of {{convert|5.4|m|ftin|sp=us}}. They were the deepest-diving Japanese submarines of the World War II, with a diving depth of {{convert|110|m|ft|abbr=on}}.<ref name=cd3>Carpenter & Dorr, p. 116</ref>

For surface running, the submarines were powered by two {{convert|1375|bhp|lk=in|0|adj=on}} [[diesel engine]]s, each driving one [[propeller shaft]]. When submerged each propeller was driven by a {{convert|2500|hp|0|adj=on}} [[electric motor]]. They could reach {{convert|15.2|kn|lk=in}} on the surface and {{convert|19|kn}} underwater. On the surface, the ''I-201'' class had a range of {{convert|5800|nmi|lk=in}} at {{convert|14|kn}}; submerged, they had a range of {{convert|135|nmi|abbr=on}} at {{convert|3|kn}}. They were fitted with a [[Submarine snorkel|snorkel]] to allow them to run their diesel engines while underwater.<ref name=c5>Chesneau, p. 202</ref>

The submarines were armed with four internal bow {{convert|53.3|cm|in|1|abbr=on|sp=us}} [[torpedo tube]]s. They carried a total of 10 [[torpedo]]es. They were also armed with two single mounts for [[Type 96 25&nbsp;mm AT/AA Gun|Type 96 25 mm]] [[anti-aircraft gun]]s.<ref name=b4>Bagnasco, p. 195</ref>

==Construction and commissioning==

Ordered as '''''Submarine No. 4503''''', ''I-203'' was [[Keel-laying|laid down]] on 1 June 1944 by the [[Kure Naval Arsenal]] at [[Kure, Hiroshima|Kure]], [[Japan]].<ref name=ijnsubsiteI203/> She was [[Ceremonial ship launching|launched]] on 20 October, and was completed and [[Ship commissioning|commissioned]] on 29&nbsp;May&nbsp;1945.<ref name=ijnsubsiteI203>{{cite web |url= http://www.ijnsubsite.info/I-Sub%20Details/I-203.htm |title=I-203 ex No-4503 |work=iijnsubsite.info |year=2018|access-date=26 October 2020}}</ref><ref name=combinedfleetI203>{{cite web |url= http://www.combinedfleet.com/I-203.htm |title=IJN Submarine I-203: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2011|access-date=26 October 2020}}</ref>

==Service history==
===World War II===

Upon commissioning, ''I-203'' was attached to the [[Kure Naval District]]<ref name=ijnsubsiteI203/> and assigned to Submarine Division 33 in the Kure Submarine [[Squadron (naval)|Squadron]].<ref name=ijnsubsiteI203/> She was reassigned on 25 June 1945 to Submarine Squadron 11 in the [[6th Fleet (Imperial Japanese Navy)|6th Fleet]].<ref name=ijnsubsiteI203/><ref name=combinedfleetI203/>

On 15 August 1945, ''I-203'' was at [[Maizuru]], Japan, with her [[sister ship]]s {{ship|Japanese submarine|I-201||2}} and {{ship|Japanese submarine|I-202||2}} when she was reassigned to Submarine Division 15 in the 6th Fleet.<ref name=ijnsubsiteI203/><ref name=combinedfleetI203/><ref name=combinedfleetI201>{{cite web |url= http://www.combinedfleet.com/I-201.htm |title=IJN Submarine I-201: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2011|access-date=26 October 2020}}</ref> The same day, hostilities between Japan and the [[Allies of World War II|Allies]] came to an end.<ref name=combinedfleetI203/> [[Surrender of Japan|Japan formally surrendered]] in a ceremony aboard the [[United States Navy]] [[battleship]] {{USS|Missouri|BB-63|6}} in [[Tokyo Bay]] on 2 September 1945,<ref name=combinedfleetI201/> and ''I-203'' surrendered to the Allies<ref name=ijnsubsiteI203/><ref name=combinedfleetI203/> at Maizuru that day.<ref name=ijnsubsiteI203/>

===Postwar===

In November 1945, ''I-203'' departed Maizuru bound for [[Sasebo]], Japan, which she reached on 25 November 1945.<ref name=combinedfleetI203/> The Japanese struck her from the Navy list on 30 November 1945.<ref name=ijnsubsiteI203/><ref name=combinedfleetI203/> On 12 December 1945, she got underway from Sasebo for [[sea trials]], manned by a U.S. Navy crew and a skeleton Imperial Japanese Navy crew.<ref name=combinedfleetI203/> Between 28 December 1945 and 8 January 1946, she and ''I-201'' put to sea from Sasebo for a series of short sea trials with U.S. Navy crews, supported by the U.S. Navy [[submarine tender]] {{USS|Euryale}}.<ref name=combinedfleetI203/>

At 07:30 on 13 January 1946, ''I-201'' and ''I-203'' got underway from Sasebo in company with ''Euryale'' and the [[rescue and salvage ship]] {{USS|Current||6}} bound for [[Pearl Harbor]], [[Hawaii]], with stops planned at [[Guam]] in the [[Mariana Islands]], [[Eniwetok]] in the [[Marshall Islands]], and [[Johnston Atoll]].<ref name=combinedfleetI203/><ref name=combinedfleetI201/> The vessels proceeded due south toward Guam in a column formation, with ''Euryale'' in the lead followed by ''I-201'', ''I-203'', and ''Current'', with each vessel {{convert|1,500|yd|m|sigfig=3}} from the vessel ahead and astern of her.<ref name=combinedfleetI201/>  While proceeding to Guam, the ships rode out a [[typhoon]], during which both submarines suffered engine breakdowns and ''I-201'' had a steering failure.<ref name=combinedfleetI203/><ref name=combinedfleetI201/> After repairs at sea, the ships arrived at [[Apra Harbor]] on Guam at 16:15 on 21 January 1946, receiving a boisterous welcome.<ref name=combinedfleetI203/><ref name=combinedfleetI201/> The crews were granted shore leave on Guam.<ref name=combinedfleetI203/>

The vessels departed Guam on 25 January 1946 on the next leg of their voyage.<ref name=combinedfleetI201/> ''I-203'' again suffered engine failure on 29 January that reportedly forced her to spend an additional night at sea,<ref name=combinedfleetI203/> although she also reportedly reached Eniwetok on 31 January 1946 along with the rest of the vessels.<ref name=combinedfleetI203/><ref name=combinedfleetI201/> The formation commander decided to skip the planned stop at Johnston Atoll and proceed directly from Eniwetok to Pearl Harbor.<ref name=combinedfleetI203/> A direct trip from Eniwetok to Pearl Harbor exceeded ''I-201''′s and ''I-203''′s range, so he ordered the two submarines to be towed.<ref name=combinedfleetI201/> At 07:00 on 2 February 1946, the vessels left Eniwetok.<ref name=combinedfleetI203/> The formation arrived at Pearl Harbor on 13 February 1946, and ''I-201'' and ''I-203'' entered a caretaker status there with skeleton crews while the U.S. Navy studied their design.<ref name=combinedfleetI203/>

==Disposal==

With postwar relations with the [[Soviet Union]] deteriorating rapidly and concerns growing in the [[United States]] that under postwar agreements the Soviets would demand access to the captured Japanese submarines that would provide the [[Soviet Navy]] with valuable information about advanced Japanese submarine designs,<ref name=combinedfleetI203/><ref>{{cite news | last = Fountain | first = Henry | title = 2 Japanese Subs Are Found in Waters Off Hawaii | work = New York Times | place =New York | date = November 12, 2009 | url = https://www.nytimes.com/2009/11/13/science/13wreck.html?hp | access-date = 26 October 2020}}</ref> the U.S. Navy issued orders on 26 March 1946 to sink all captured Japanese submarines. Accordingly, the U.S. Navy sank ''I-203'' as a target in tests of the Mark 9 exploder off Pearl Harbor on 21 May 1946. She sank at 11:43 at {{coord|21|13|N|158|08|W|name=''I-203''}} after the submarine {{USS|Caiman}} hit her with a [[Mark 18 torpedo|Mark 18 Mod 2 torpedo]].<ref name=combinedfleetI203/>

== Notes==
{{reflist|30em}}

==References==
*{{cite book|last=Bagnasco |first=Erminio |title=Submarines of World War Two |year=1977 |publisher=Naval Institute Press |location=Annapolis, Maryland |isbn=0-87021-962-6}} 
*{{cite book|last1=Carpenter|first1=Dorr B.|last2=Polmar|first2=Norman|title=Submarines of the Imperial Japanese Navy 1904–1945|year=1986|publisher=Conway Maritime Press|location=London|isbn=0-85177-396-6|name-list-style=amp}}
*{{cite book|title=Conway's All the World's Fighting Ships 1922–1946|editor1-last=Chesneau|editor1-first=Roger|publisher=Conway Maritime Press|location=Greenwich, UK|year=1980|isbn=0-85177-146-7}}
*{{cite web |url= http://www.combinedfleet.com/I-201.htm |title=IJN Submarine I-201: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2012|access-date=1 March 2012}}
*{{cite book|last=Rohwer|first=Jürgen|title=Chronology of the War at Sea 1939–1945: The Naval History of World War Two|publisher=Naval Institute Press|location=Annapolis, Maryland|year=2005|edition=Third Revised|isbn=1-59114-119-2|author-link=Jürgen Rohwer}}

{{I-201 class submarine}}
{{1946 shipwrecks}}

{{DEFAULTSORT:I-203}}
[[Category:World War II submarines of Japan]]
[[Category:I-201-class submarines]]
[[Category:1944 ships]]
[[Category:Ships built by Kure Naval Arsenal]]
[[Category:Maritime incidents in 1946]]
[[Category:Ships sunk as targets]]
[[Category:Shipwrecks in the Pacific Ocean]]