View source for Japanese submarine Ro-46

{{short description|Kaichū-type submarine}}
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{{Infobox ship career
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|Ship country=Japan
|Ship flag= {{Shipboxflag|Empire of Japan|naval}}
|Ship name=''Submarine No. 387''
|Ship namesake=
|Ship ordered=
|Ship builder=[[Mitsubishi Heavy Industries|Mitsubishi]], [[Kobe]], [[Japan]]
|Ship laid down=13 June 1942
|Ship renamed=''Ro-46'' on 5&nbsp;February&nbsp;1943
}}
{{Infobox ship career
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|Ship launched=23 May 1943
|Ship completed=19 February 1944
|Ship acquired=
|Ship commissioned=19 February 1944
|Ship decommissioned=
|Ship in service=
|Ship out of service=
|Ship fate=Missing after 17&nbsp;April&nbsp;1945
|Ship reinstated=
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{{Infobox ship career
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|Ship struck=10 June 1945
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{{Infobox ship characteristics
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|Ship class=[[Kaichū type submarine]] (K6 subclass)
|Ship displacement=*{{Convert|1115|LT|t|0|disp=flip}} surfaced
*{{Convert|1447|LT|t|0|disp=flip}} submerged
|Ship length={{convert|80.5|m|ftin|abbr=on}} overall
|Ship beam= {{convert|7|m|ftin|abbr=on}}
|Ship draft={{convert|4.07|m|ftin|abbr=on}}
|Ship power=*{{convert|4200|bhp|lk=in|abbr=on}} (diesel)
*{{convert|1200|hp|abbr=on}} ([[electric motor]])
|Ship propulsion=*[[Diesel-electric]]
*1 × [[diesel engine]]
*1 × electric motor
|Ship speed=*{{convert|19.75|kn|lk=in}} surfaced
*{{convert|8|kn}} submerged
|Ship range=*{{convert|5000|nmi|abbr=on|lk=in}} at {{convert|16|kn}} surfaced
*{{convert|45|nmi|abbr=on}} at {{convert|5|kn}} submerged
|Ship crew=61
|Ship test depth={{convert|80|m|ft|abbr=on}}
|Ship armament=*4 × bow {{convert|533|mm|in|0|abbr=on}} [[torpedo tubes]]
*1 × [[8 cm/40 3rd Year Type naval gun|{{convert|76.2|mm|in|abbr=on}}]] L/40 [[anti-aircraft gun]]
*2 × single [[Type 96 25 mm AT/AA Gun|{{convert|25|mm|in|1|abbr=on}} AA guns]]
|Ship notes=
}}
|}
'''''Ro-46''''' was an [[Imperial Japanese Navy]] [[Kaichū type submarine]] of the K6 [[ship class|sub-class]]. Completed and commissioned in February 1944, she served in [[World War II]], including operations related to the [[Marianas campaign]], the [[Philippines campaign (1944–1945)|Philippines campaign]], and the [[Battle of Okinawa]]. She disappeared in April 1945 during her fifth war patrol.

==Design and description==
The submarines of the K6 sub-class were versions of the preceding K5 sub-class with greater range and diving depth.<ref name=cd3/> They [[Displacement (ship)|displaced]] {{Convert|1115|LT|t|0|disp=flip}} surfaced and {{Convert|1447|LT|t|0|disp=flip}} submerged. The submarines were {{convert|80.5|m|ftin|sp=us}} long, had a [[beam (nautical)|beam]] of {{convert|7|m|ftin|sp=us}} and a [[draft (hull)|draft]] of {{convert|4.07|m|ftin|sp=us}}. They had a diving depth of {{convert|80|m|ft|sp=us}}.<ref name=b4>Bagnasco, p. 187</ref>

For surface running, the boats were powered by two {{convert|2100|bhp|lk=in|0|adj=on}} [[diesel engine]]s, each driving one [[propeller shaft]]. When submerged each propeller was driven by a {{convert|600|hp|0|adj=on}} [[electric motor]].<ref name=c5>Chesneau, p. 203</ref> They could reach {{convert|19.75|kn|lk=in}} on the surface and {{convert|8|kn}} underwater. On the surface, the K6s had a range of {{convert|11000|nmi|lk=in}} at {{convert|12|kn}}; submerged, they had a range of {{convert|45|nmi|abbr=on}} at {{convert|5|kn}}.<ref name=cd3/>

The boats were armed with four internal bow {{convert|53.3|cm|in|1|abbr=on|sp=us}} [[torpedo tube]]s and carried a total of ten [[torpedo]]es. They were also armed with a single [[8 cm/40 3rd Year Type naval gun|{{convert|76.2|mm|in|abbr=on}}]] L/40 [[anti-aircraft gun]] and two single [[Type 96 25 mm AT/AA Gun|{{convert|25|mm|in|1|abbr=on}} AA guns]].<ref name=cd3>Carpenter & Dorr, p. 124</ref>

==Construction and commissioning==

''Ro-46'' was [[Keel-laying|laid down]] as '''''Submarine No. 387''''' on 13 June 1942 by [[Mitsubishi Heavy Industries]] at [[Kobe]], [[Japan]].<ref name=combinedfleetRo46>{{cite web |url= http://www.combinedfleet.com/RO-46.htm |title=IJN Submarine RO-46: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=24 September 2020}}</ref> She was renamed '''''Ro-46''''' on 5 February 1943 and was attached provisionally to the [[Maizuru Naval District]] that day.<ref name=combinedfleetRo46/> She was [[Ceremonial ship launching|launched]] on 23 May 1943 and was completed and [[Ship commissioning|commissioned]] on 19&nbsp;February&nbsp;1944.<ref name=combinedfleetRo46/>

==Service history==
Upon commissioning, ''Ro-46'' was attached formally to the Maizuru Naval District.<ref name=combinedfleetRo46/> She called at [[Tokuyama, Yamaguchi|Tokuyama]] to refuel from 28 to 29 March 1944.<ref name=combinedfleetRo46/> During a workup cruise, she was involved in an underwater collision with the submarine {{ship|Japanese submarine|I-46||2}} in the ''Iyo-nada'' in the [[Seto Inland Sea]] off [[Minase Light]] at 21:45 on 2 April 1944, suffering damage to her [[conning tower]].<ref name=combinedfleetRo46/>

===First war patrol===

On 23 June 1944, ''Ro-46'' was reassigned to Submarine Division 34 in the [[6th Fleet (Imperial Japanese Navy)|6th Fleet]],<ref name=combinedfleetRo46/> and she departed [[Kure, Hiroshima|Kure]], Japan, to begin her first war patrol, assigned a patrol area in the [[Mariana Islands]] off [[Saipan]], where the [[Battle of Saipan]] had been raging since 15 June.<ref name=combinedfleetRo46/> U.S. forces attacked and damaged her on 3 July 1944, forcing her to return to Kure on 8 July 1944 for repairs.<ref name=combinedfleetRo46/>

===Second war patrol===

With her repairs complete, ''Ro-46'' set out from Kure on 19 September 1944 to begin her second war patrol, assigned a patrol area southwest of [[Palau]].<ref name=combinedfleetRo46/> She sighted a [[United States Navy]] [[aircraft carrier]] on 28 September 1944, but was too far away to attack.<ref name=combinedfleetRo46/> She sighted another aircraft carrier on 1 October 1944, but again did not attack.<ref name=combinedfleetRo46/>

On 2 October 1944, ''Ro-46'' received orders to join the submarine {{ship|Japanese submarine|I-177||2}} in a reconnaissance of the American fleet anchorage at [[Ulithi Atoll]], with ''Ro-46'' approaching the [[atoll]] from the west while ''I-177'' approached it from the east.<ref name=combinedfleetRo46/> The information they gathered was intended to support the first ''[[kaiten]]'' [[suicide attack]] [[torpedo]] operation against the anchorage.<ref name=combinedfleetRo46/> ''Ro-46'' made her [[periscope]] reconnaissance of the anchorage on 7 October, reporting the aircraft carrier {{USS|Bunker Hill|CV-17}}, two [[heavy cruiser]]s, and their escorts there.<ref name=combinedfleetRo46/> She returned to Kure on 14 October 1944.<ref name=combinedfleetRo46/>

===Third war patrol===

On 13 October 1944, the day before ''Ro-46''′s arrival at Kure, the Combined Fleet activated Operation Shō-Gō 1 for the defense of the [[Philippine Islands]].<ref name=combinedfleetRo46/> The [[Philippines campaign (1944–1945)|Philippines campaign]] and the [[Battle of Leyte]] began with the U.S. landings on [[Leyte]] on 20 October 1944, and that day ''Ro-46'' got back underway from Kure for her third war patrol, ordered to operate as part of Submarine Group B and assigned a patrol area in the [[Philippine Sea]] east of the Philippines.<ref name=combinedfleetRo46/> The Japanese naval reaction to the invasion of Leyte resulted in the [[Battle of Leyte Gulf]] of 23–26 October 1944. ''Ro-46'' saw no action during the battle, and on 7 November 1944 the 6th Fleet ordered all submarines in the Philippines area to return to Japan.<ref name=combinedfleetRo46/> On 13 November 1944, during her voyage to Japan, ''Ro-46'' rescued the pilot of an [[Imperial Japanese Army Air Force]] [[Nakajima Ki-43|Nakajima Ki-43 Hayabusa]] ("Peregrine Falcon"; [[World War II Allied names for Japanese aircraft|Allied reporting name]] "Oscar") [[Fighter aircraft|fighter]] shot down during combat over [[Manila]].<ref name=combinedfleetRo46/> She arrived at Maizuru on 19 November 1944.<ref name=combinedfleetRo46/>

===Fourth war patrol===

On 8 January 1945, ''Ro-46'' put to sea from Kure for her fourth war patrol, with a patrol area in the [[South China Sea]] west of Luzon.<ref name=combinedfleetRo46/> U.S. forces entered [[Lingayen Gulf]] and U.S. forces began their [[Invasion of Lingayen Gulf|invasion]] of [[Luzon]] on 9 January 1945.<ref name=combinedfleetRo46/> On 29 January 1945, ''Ro-46'' torpedoed the [[attack transport]] {{USS|Cavalier|APA-37}} at {{coord|14|48|N|119|18|E}};<ref name=combinedfleetRo46/> although ''Cavalier'' survived, she had to be [[Towing|towed]] to Leyte.<ref name=combinedfleetRo46/> {{nowrap|''Ro-46''}} reported sinking a [[fleet oiler]] from a [[convoy]] at 01:13 on 30 January 1945, then departed the area.<ref name=combinedfleetRo46/>

On 2 or 4 February 1945 (sources differ), the 6th Fleet ordered ''Ro-46'' and the submarines {{ship|Japanese submarine|Ro-112||2}}, {{ship|Japanese submarine|Ro-113||2}}, and {{ship|Japanese submarine|Ro-115||2}} to proceed to [[Kaohsiung|Takao]], [[Formosa]], unload their reserve torpedoes and [[deck gun]] ammunition there, and then head for [[Batulinao]] on the northern coast of Luzon to rescue [[Imperial Japanese Navy Air Service]] pilots stranded in Luzon's [[Aparri]] area and transport them to Takao.<ref name=combinedfleetRo46/><ref>{{cite web |url= http://www.combinedfleet.com/RO-112.htm |title=IJN Submarine RO-112: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=5 October 2020}}</ref> ''Ro-46'' arrived at [[Kaohsiung|Takao]] on [[Taiwan|Formosa]] on 4 February 1945.<ref name=combinedfleetRo46/>

At Takao, ''Ro-46''′s orders were modified to require her to transport fuel and ammunition to the Japanese forces fighting on Luzon, rescue at least 40 pilots from Batulinao, then proceed directly to [[Sasebo]], Japan.<ref name=combinedfleetRo46/> She departed Takao on 7 February 1945 and arrived at Batulinao just before midnight on 10 February.<ref name=combinedfleetRo46/> After unloading her cargo into [[Daihatsu-class landing craft|''Daihatsu''-class]] [[landing craft]] operated by the [[Imperial Japanese Army]], she embarked 46 pilots and got back underway the same night.<ref name=combinedfleetRo46/> She transported the pilots to Takao, which she reached on 12 February 1945.<ref name=combinedfleetRo46/>

On 13 February 1945, ''Ro-46'' departed Takao to return to Japan, ordered to conduct a reconnaissance of the [[Ryukyu Islands]] while en route.<ref name=combinedfleetRo46/> She arrived at Kure on 19 February 1945.<ref name=combinedfleetRo46/>

===Fifth war patrol===
''Ro-46'' got underway from Kure on 6 April 1945 for her fifth war patrol, assigned a patrol area northeast of [[Kitadaitōjima]], which lies in the southern Ryukyu Islands southeast of [[Okinawa Island|Okinawa]], where the [[Battle of Okinawa]] had begun on 1 April 1945.<ref name=combinedfleetRo46/> On 17 April 1945, she transmitted a report to the 6th Fleet from a position {{convert|60|nmi}} northeast of Kitadaitōjima.<ref name=combinedfleetRo46/> The Japanese never heard from her again.<ref name=combinedfleetRo46/>

===Loss===
The circumstances of the loss of ''Ro-46'' remain unknown.<ref name=combinedfleetRo46/> Some sources credit the U.S. Navy submarine {{USS|Sea Owl|SS-405}} with sinking her northeast of [[Wake Island]] on 18 April 1945, but ''Ro-46'' was operating far from Wake Island and the Japanese submarine ''Sea Owl'' attacked was {{ship|Japanese submarine|I-372||2}} — which survived the attack.<ref name=combinedfleetRo46/> It is possible that aircraft of U.S. Navy [[VC-92|Composite Squadron 92 (VC-92)]] operating from the [[escort aircraft carrier]] {{USS|Tulagi|CVE-72}} sank ''Ro-46'' at {{coord|24|15|N|131|16|E|name=''Ro-46''}} on 29 April 1945.<ref name=combinedfleetRo46/>

On 2 May 1945, the Imperial Japanese Navy declared ''Ro-46'' to be presumed lost in the Okinawa area with all 86 men on board.<ref name=combinedfleetRo46/> She was stricken from the Navy list on 10 June 1945.<ref name=combinedfleetRo46/>

==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/RO-46.htm|title=IJN Submarine RO-46: Tabular Record of Movement|last1=Hackett|first1=Bob|last2=Kingsepp|first2=Sander|year=2017|work=SENSUIKAN! Stories and Battle Histories of the IJN's Submarines|publisher=Combinedfleet.com|access-date=24 September 2020}}
* {{cite web|url=http://www.combinedfleet.com/type_kaichu.htm|title=Kaichu Type|last=Hackett|first=Bob |author2=Sander Kingsepp |year=2003|work=Sensuikan!|publisher=Combinedfleet.com|access-date=20 September 2020}}
*{{cite book|last=Hashimoto|first=Mochitsura|others=Colegrave, E.H.M. (translator)|title=Sunk: The Story of the Japanese Submarine Fleet 1942 – 1945|publisher=Cassell and Company|location=London|year=1954|id=ASIN B000QSM3L0}}
{{Kaichū type submarine}}
{{April 1944 shipwrecks}}
{{April 1945 shipwrecks}}

{{DEFAULTSORT:Ro-046}}
[[Category:Ro-35-class submarines]]
[[Category:Kaichū type submarines]]
[[Category:Ships built by Mitsubishi Heavy Industries]]
[[Category:1943 ships]]
[[Category:Japanese submarines lost during World War II]]
[[Category:World War II submarines of Japan]]
[[Category:World War II shipwrecks in the Pacific Ocean]]
[[Category:Maritime incidents in April 1944]]
[[Category:Maritime incidents in April 1945]]
[[Category:Missing submarines of World War II]]
[[Category:Warships lost with all hands]]
[[Category:Submarines lost with all hands]]