View source for Japanese submarine Ro-106

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|Ship country=Japan
|Ship flag= {{Shipboxflag|Empire of Japan|naval}}
|Ship name=''Submarine No. 216''
|Ship namesake=
|Ship ordered=
|Ship builder=[[Kure Naval Arsenal]], [[Kure, Hiroshima|Kure]], [[Japan]]
|Ship laid down=17 December 1941
|Ship renamed=''Ro-106'' on 8 April 1942
}}
{{Infobox ship career
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|Ship launched=30 May 1942
|Ship completed26 December 1942
|Ship acquired=
|Ship commissioned=26 December 1942
|Ship decommissioned=
|Ship in service=
|Ship out of service=
|Ship fate=Sunk 22 May 1944
|Ship reinstated=
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{{Infobox ship career
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|Ship struck=10 August 1944
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{{Infobox ship characteristics
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|Ship class= {{sclass|Ro-100|submarine}}
|Ship displacement=*{{Convert|601|LT|t|0|disp=flip}} surfaced
*{{Convert|782|LT|t|0|disp=flip}} submerged
|Ship length={{convert|60.90|m|ftin|abbr=on}} overall
|Ship beam= {{convert|6.00|m|ftin|abbr=on}}
|Ship draft={{convert|3.51|m|ftin|abbr=on}}
|Ship power=*{{convert|1000|bhp|lk=in|abbr=on}} (diesel)
*{{convert|760|hp|abbr=on}} ([[electric motor]])
|Ship propulsion=*[[Diesel-electric]]
*1 × [[diesel engine]]
*1 × electric motor
|Ship speed=*{{convert|14.2|kn|lk=in}} surfaced
*{{convert|8|kn}} submerged
|Ship range=*{{convert|3500|nmi|abbr=on|lk=in}} at {{convert|12|kn}} surfaced
*{{convert|60|nmi|abbr=on}} at {{convert|3|kn}} submerged
|Ship crew=38
|Ship test depth={{convert|75|m|ft|abbr=on}}
|Ship armament=*4 × bow {{convert|533|mm|in|0|abbr=on}} [[torpedo tubes]]
*2 × [[Type 96 25 mm AT/AA Gun|{{convert|25|mm|in|0|abbr=on}} Type 96]] [[anti-aircraft gun]]s or 1 × [[8 cm/40 3rd Year Type naval gun|{{convert|76.2|mm|in|abbr=on}}]] L/40 AA gun
|Ship notes=
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|}
'''''Ro-106''''' was an [[Imperial Japanese Navy]] [[Ro-100-class submarine|''Ro-100''-class]] [[submarine]]. Completed and commissioned in December 1942, she served in [[World War II]], operating in the [[Solomon Islands campaign]], [[New Guinea campaign]], and central [[Pacific Ocean]]. She was sunk in May 1944 during her eleventh war patrol.

==Design and description==
The ''Ro-100'' class was a medium-sized, coastal submarine derived from the preceding [[Kaichū type submarine|''Kaichū'' type]]. They [[Displacement (ship)|displaced]] {{Convert|601|LT|t|0|disp=flip}} surfaced and {{Convert|782|LT|t|0|disp=flip}} submerged. The submarines were {{convert|60.9|m|ftin|sp=us}} long, had a [[beam (nautical)|beam]] of {{convert|6|m|ftin|sp=us}} and a [[draft (hull)|draft]] of {{convert|3.51|m|ftin|sp=us}}. They had a [[double hull]] and a diving depth of {{convert|75|m|ft|sp=us}}.<ref name=cd3>Carpenter & Dorr, p. 123</ref>

For surface running, the boats were powered by two {{convert|500|bhp|lk=in|0|adj=on}} [[diesel engine]]s, each driving one [[propeller shaft]]. When submerged each propeller was driven by a {{convert|380|hp|0|adj=on}} [[electric motor]]. They could reach {{convert|14.2|kn|lk=in}} on the surface and {{convert|8|kn}} underwater. On the surface, the ''Ro-100''s had a range of {{convert|3500|nmi|lk=in}} at {{convert|12|kn}}; submerged, they had a range of {{convert|60|nmi|abbr=on}} at {{convert|3|kn}}.<ref name=c5>Chesneau, p. 204</ref>

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 eight [[torpedo]]es. They were also armed with two single mounts for [[Type 96 25 mm AT/AA Gun|{{convert|25|mm|in|0|abbr=on}} Type 96]] [[anti-aircraft gun]]s or a single [[8 cm/40 3rd Year Type naval gun|{{convert|76.2|mm|in|abbr=on}}]] L/40 AA gun.<ref name=b4>Bagnasco, p. 193</ref>

==Construction and commissioning==

''Ro-106'' was [[Keel-laying|laid down]] as '''''Submarine No. 216''''' on 17 December 1941 by the [[Kure Naval Arsenal]] at [[Kure, Hiroshima|Kure]], [[Japan]].<ref name=combinedfleetRo106>{{cite web |url= http://www.combinedfleet.com/RO-106.htm |title=IJN Submarine RO-106: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2007|access-date=2 October 2020}}</ref> She was renamed '''''Ro-106''''' on 8 April 1942 and was [[Ceremonial ship launching|launched]] on 30 May 1942.<ref name=combinedfleetRo106/> She was completed and [[Ship commissioning|commissioned]] on 26&nbsp;December&nbsp;1942.<ref name=combinedfleetRo106/>

==Service history==
Upon commissioning, ''Ro-106'' was attached to the [[Sasebo Naval District]] and was assigned to Submarine [[Squadron (naval)|Squadron]] 11.<ref name=combinedfleetRo106/> While on workups in the [[Hayase Seto]] off Kure on 15 February 1943, her [[rudder]] jammed and she ran aground and suffered [[Hull (ship)|hull]] damage.<ref name=combinedfleetRo106/> She was [[Towing|towed]] to Kure for repairs.<ref name=combinedfleetRo106/> On 15 March 1943, she was reassigned to Submarine Squadron 7 in the [[8th Fleet (Imperial Japanese Navy)|8th Fleet]] in the [[Southeast Area Fleet]].<ref name=combinedfleetRo106/> She departed [[Sasebo]] on 31 March 1943 bound for [[Rabaul]] on [[New Britain]], which she reached on 12 April 1943.<ref name=combinedfleetRo106/>

===First, second, and third war patrols===

''Ro-106'' got underway from Rabaul on 22 April 1943 for her first war patrol, assigned a patrol area southeast of [[Guadalcanal]] in the [[Solomon Islands (archipelago)|Solomon Islands]].<ref name=combinedfleetRo106/> It was uneventful, and she returned to Rabaul on 14 May 1943.<ref name=combinedfleetRo106/> She put to sea to begin her second war patrol on 27 May 1943, but [[diesel engine]] trouble forced her to return to Rabaul on 29 May 1943.<ref name=combinedfleetRo106/> She began her third war patrol on 31 May 1943, bound again for a patrol area southeast of Guadalcanal.<ref name=combinedfleetRo106/> After another quiet patrol, she set course for Rabaul, which she reached on 16 June 1943.<ref name=combinedfleetRo106/>

===Fourth war patrol===

On 30 June 1943, the [[New Georgia campaign]] began with the U.S. landings on [[New Georgia]], [[Rendova Island|Rendova]], and other islands in the central Solomons. ''Ro-106'' departed Rabaul that day to begin her fourth war patrol, assigned a patrol area off Rendova.<ref name=combinedfleetRo106/> On 18 July 1943, she [[torpedo]]ed the [[United States Navy]] [[Landing Ship, Tank|tank landing ship]] {{USS|LST-342}} in the [[Blanche Channel]] off New Georgia at {{coord|09|03|S|158|11|E|name=''LST-342''}}.<ref name=combinedfleetRo106/> The torpedo blew ''LST-342'' in half;<ref name=combinedfleetRo106/> her [[stern]] section sank immediately, but her [[Bow (ship)|bow]] section remained afloat and was towed to [[Purvis Bay]], beached on [[Gavutu]], and stripped of usable materials and equipment.<ref name=combinedfleetRo106/> Meanwhile, ''Ro-106'' concluded her patrol with her return to Rabaul on 21 July 1943.<ref name=combinedfleetRo106/>

===Fifth and sixth war patrols===

''Ro-106'' set out from Rabaul on 31 July 1943 to begin her fifth war patrol.<ref name=combinedfleetRo106/> It was uneventful, and on 20 August 1943 she returned to Rabaul, where she was reassigned to the new Submarine Division 51 along with the submarines {{ship|Japanese submarine|Ro-100||2}}, {{ship|Japanese submarine|Ro-101||2}}, {{ship|Japanese submarine|Ro-103||2}}, {{ship|Japanese submarine|Ro-104||2}}, and {{ship|Japanese submarine|Ro-105||2}}, with ''Ro-105'' serving as squadron [[flagship]].<ref name=combinedfleetRo106/> She departed Rabaul on 1 September 1943 for her sixth war patrol, assigned a patrol area off [[Makira|San Cristobal]] in the southeastern Solomon Islands.<ref name=combinedfleetRo106/> She found no targets, and on 22 September 1943 received orders to divert from her patrol to rescue [[Imperial Japanese Navy Air Service]] aviators who had been shot down on 20 September.<ref name=combinedfleetRo106/> She then made for Rabaul, where she arrived on 24 September 1943.<ref name=combinedfleetRo106/>

===New Guinea campaign===
On 6 October 1943, ''Ro-106'' departed Rabaul to carry supplies to [[Sarmi Regency|Sarmi]] on the northern coast of [[New Guinea]] in support of Japanese forces fighting in the [[New Guinea campaign]].<ref name=combinedfleetRo106/> She reached Sarmi on 7 October 1943, unloaded her cargo, and got back underway the same night.<ref name=combinedfleetRo106/> Rather than return to Rabaul, she received orders on 9 October 1943 to operate off [[Lae]], New Guinea, conducting her seventh war patrol.<ref name=combinedfleetRo106/> She was off Lae on 19 October 1943 when an [[Allies of World War II|Allied]] plane spotted her and reported her to Allied warships, probably including the U.S. Navy [[destroyer]] {{USS|Mahan|DD-364}}, which reported [[Depth charge|depth-charging]] a submarine off Lae that day.<ref name=combinedfleetRo106/> She suffered serious damage in the depth-charge attacks the Allied ships conducted against her, and after calling at Rabaul from 23 to 27 October 1943 she proceeded to Sasebo, which she reached on 8 November 1943 to undergo repairs.<ref name=combinedfleetRo106/>

With her repairs complete, ''Ro-106'' departed Sasebo on 16 December 1943 bound for Rabaul,<ref name=combinedfleetRo106/> where she arrived on 29 December 1943.<ref name=combinedfleetRo106/> After a little over a month there, she set out for her second supply run to Sarmi on 1 February 1944.<ref name=combinedfleetRo106/> She called at Sarmi on 3 February and returned to Rabaul on 5 February 1944.<ref name=combinedfleetRo106/> Another supply run to Sarmi followed, with ''Ro-106'' departing Rabaul on 10 February 1944, discharging her cargo on 12 February, and returning to Rabaul on 14 February 1944.<ref name=combinedfleetRo106/>

===Eighth war patrol===

On 19 February 1944, ''Ro-106'' was reassigned to the 1st Advance Submarine Unit and set out from Rabaul for her eighth war patrol, ordered to operate within a {{convert|90|nmi|adj=on}} radius of [[Tonowas|Natsushima]] at [[Chuuk Lagoon|Truk]]<ref name=combinedfleetRo106/> to intercept U.S. Navy [[Task Force 58]], which had made a major air and surface attack against Truk on 17–18 February 1944  in [[Operation Hailstone]]. She found no targets, and on 1 March 1944 received orders to move to the [[Eniwetok]] area.<ref name=combinedfleetRo106/> She conducted a [[periscope]] reconnaissance of Eniwetok on 4 March 1944 and found no ships there, but when she returned to reconnoiter the [[atoll]] again on 5 March 1944 she sighted what she reported as several [[cruiser]]s, destroyers, and a [[repair ship]] there.<ref name=combinedfleetRo106/> She returned to Truk on 8 March 1944, the day on which Truk-based [[Mitsubishi G4M]] ([[World War II Allied names for Japanese aircraft|Allied reporting name]] "Betty") [[bomber]]s of the 705th Naval Air Group raided the anchorage at Eniwetok to attack the ships she had sighted.<ref name=combinedfleetRo106/>

===Ninth and tenth war patrols===

Two uneventful war patrols from Truk followed. ''Ro-106'' began her ninth patrol on 17 March 1944, bound for a patrol area southeast of Truk and north of the [[Nomoi Islands]].<ref name=combinedfleetRo106/> She called at Truk from 24 to 29 March 1944, then set out on her tenth war patrol, assigned a patrol area east of Eniwetok.<ref name=combinedfleetRo106/> She returned to Truk on 20 April 1944.<ref name=combinedfleetRo106/> She again [[sortie]]d from Truk on 30 April 1944 to intercept an Allied [[task force]], but found no enemy ships and returned to Truk on 3 May 1944.<ref name=combinedfleetRo106/>

===Eleventh war patrol===

''Ro-106'' got underway from Truk on 16 May 1944 for her eleventh war patrol, ordered to join the submarines {{ship|Japanese submarine|Ro-104||2}}, {{ship|Japanese submarine|Ro-105||2}}, {{ship|Japanese submarine|Ro-108||2}}, {{ship|Japanese submarine|Ro-109||2}}, {{ship|Japanese submarine|Ro-112||2}}, and {{ship|Japanese submarine|Ro-116||2}}<ref name=combinedfleetRo105>{{cite web |url= http://www.combinedfleet.com/RO-105.htm |title=IJN Submarine RO-105: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=30 September 2020}}</ref> in forming a submarine picket line north of the [[Admiralty Islands]] designated Scouting Line NA.<ref name=combinedfleetRo106/><ref name=combinedfleetRo105/> The picket line was tasked with providing warning of any move toward the [[Palau Islands]] by Allied invasion forces.<ref name=combinedfleetRo106/> After ''Ro-106'' departed Truk, the Japanese never heard from her again.<ref name=combinedfleetRo106/>

On 18 May 1944, U.S. Navy [[signals intelligence]] personnel intercepted and decrypted Japanese signals indicating the formation of Scouting Line NA between Truk and the Admiralties.<ref name=combinedfleetRo106/>  A U.S. Navy [[hunter-killer group]] composed of the [[destroyer escort]]s {{USS|England|DE-635}}, {{USS|George|DE-697}}, and {{USS|Raby|DE-698}} departed Purvis Bay in the Solomon Islands to intercept the submarine {{ship|Japanese submarine|I-16||2}}, then attack the submarines assigned to Scouting Line NA.<ref name=combinedfleetRo106/><ref name=combinedfleetI16>{{cite web |url= http://www.combinedfleet.com/I-16.htm |title=IJN Submarine I-16: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=26 August 2020}}</ref> After ''England'' sank ''I-16'' on 19 May 1944,<ref name=combinedfleetI16/> the hunter-killer group turned its attention to Scouting Line NA.

===Loss===

''Ro-106'' was on the surface north of the Admiralty Islands at 03:51 on 22 May 1944 when ''George'' established [[radar]] contact on her at a range of {{convert|14,000|yd|m|sigfig=3}} bearing 303 degrees from ''George''.<ref name=combinedfleetRo106/> Shortly thereafter, ''England'' also detected ''Ro-106'' on radar and assessed the contact as a surfaced submarine.<ref name=combinedfleetRo106/> While ''George'' and ''Raby'' closed the range, ''England'' steamed northeast to cut off ''Ro-106''′s escape.<ref name=combinedfleetRo106/>

''Ro-106''′s [[radar detector]] apparently did not detect the radar signals from the approaching destroyer escorts and she was still on the surface when ''George'' illuminated her with [[searchlight]]s at a range of {{convert|4,000|yd|m|sigfig=2}}.<ref name=combinedfleetRo106/> She crash-dived and began radical maneuvers to disrupt and confuse the [[sonar]]s aboard the destroyer escorts and avoid hits by their [[Antisubmarine warfare|antisubmarine]] weapons.<ref name=combinedfleetRo106/> ''George'' achieved sonar contact on her at 04:10 and fired a barrage of [[Hedgehog (weapon)|Hedgehog]] projectiles, but missed.<ref name=combinedfleetRo106/>

At 04:25, ''England'' detected ''Ro-106'' on sonar at a range of {{convert|2,500|yd|m|sigfig=2}} bearing 193 degrees from ''England''.<ref name=combinedfleetRo106/> ''England'' launched an unsuccessful Hedgehog attack, then opened the range, turned back, and closed for another attack.<ref name=combinedfleetRo106/> ''Ro-106'' also reversed course and approached ''England'' head-on.<ref name=combinedfleetRo106/> ''England'' made her second Hedgehog attack at 05:01, resulting in three underwater explosions at a depth for {{convert|275|ft|m|0}}.<ref name=combinedfleetRo106/> ''Ro-106'' sank with all hands in {{convert|16,200|ft|m|sigfig=3}} of water at {{coord|01|40|N|150|31|E|name=''Ro-106''}}.<ref name=combinedfleetRo106/>

''Ro-106'' was the second of six Japanese submarines ''England'' sank over a 13-day period in May 1944:<ref name=danfsengland>[https://www.history.navy.mil/research/histories/ship-histories/danfs/e/england.html Dictionary of American Naval Fighting Ships ''England'' I (DE-635} Accessed 13 June 2022]</ref> She previously had sunk {{ship|Japanese submarine|I-16||2}} on 19 May,<ref name=danfsengland/><ref name=combinedfleetI16>{{cite web |url= http://www.combinedfleet.com/I-16.htm |title=IJN Submarine I-16: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=26 August 2020}}</ref> and she went on to sink {{ship|Japanese submarine|Ro-104||2}} on 23 May,<ref name=danfsengland/><ref>{{cite web |url= http://www.combinedfleet.com/RO-104.htm |title=IJN Submarine RO-104: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=29 September 2020}}</ref> {{ship|Japanese submarine|Ro-116||2}} on 24 May,<ref name=danfsengland/><ref>{{cite web |url= http://www.combinedfleet.com/RO-116.htm |title=IJN Submarine RO-116: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=5 October 2020}}</ref> {{ship|Japanese submarine|Ro-108||2}} on 26 May,<ref name=danfsengland/><ref>{{cite web |url= http://www.combinedfleet.com/RO-108.htm |title=IJN Submarine RO-108: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|accessdate=3 October 2020}}</ref> and {{ship|Japanese submarine|Ro-105||2}} on 31 May.<ref name=danfsengland/><ref>{{cite web |url= http://www.combinedfleet.com/RO-105.htm |title=IJN Submarine RO-105: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=30 September 2020}}</ref>

On 15 June 1944, the Imperial Japanese Navy declared ''Ro-106'' to be presumed lost north of the Admiralty Islands with all 49 men on board.<ref name=combinedfleetRo106/> The Japanese struck her from the Navy list on 10 August 1944.<ref name=combinedfleetRo106/>

==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-106.htm|title=IJN Submarine RO-106: Tabular Record of Movement|last1=Hackett|first1=Bob|last2=Kingsepp|first2=Sander|year=2007|work=SENSUIKAN! Stories and Battle Histories of the IJN's Submarines|publisher=Combinedfleet.com|access-date=18 August 2015}}

==External links==
* [https://web.archive.org/web/20120401011058/http://wwiiarchives.net/servlet/ship/493 Ro-106]

{{Ro-100 class submarines}}
{{February 1943 shipwrecks}}
{{May 1944 shipwrecks}}

{{DEFAULTSORT:Ro-106}}
[[Category:1942 ships]]
[[Category:Ships built by Kure Naval Arsenal]]
[[Category:World War II submarines of Japan]]
[[Category:Japanese submarines lost during World War II]]
[[Category:Ro-100-class submarines]]
[[Category:Maritime incidents in February 1943]]
[[Category:Maritime incidents in May 1944]]
[[Category:World War II shipwrecks in the Pacific Ocean]]
[[Category:Submarines sunk by United States warships]]
[[Category:Warships lost in combat with all hands]]
[[Category:Submarines lost with all hands]]