View source for Japanese submarine Ro-66

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|Ship country=Japan
|Ship flag= {{Shipboxflag|Empire of Japan|naval}}
|Ship name=''Ro-66''
|Ship namesake=
|Ship ordered=
|Ship builder=[[Mitsubishi Heavy Industries|Mitsubishi]], [[Kobe]], [[Japan]]
|Ship laid down=1 December 1925
|Ship launched=25 October 1926
|Ship completed=28 July 1927
|Ship acquired=
|Ship commissioned=28 July 1927
|Ship decommissioned=15 November 1930
}}
{{Infobox ship career
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|Ship recommissioned=1 May 1931
|Ship decommissioned=15 November 1933
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{{Infobox ship career
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|Ship recommissioned=15 November 1934
|Ship decommissioned=Possibly&nbsp;15&nbsp;November&nbsp;1938 (see&nbsp;text)
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{{Infobox ship career
|Hide header=yes
|Ship recommissioned=Possibly&nbsp;15&nbsp;November&nbsp;1940 (see&nbsp;text)
|Ship decommissioned=
|Ship in service=
|Ship out of service=
|Ship fate=Sunk in collision 17&nbsp;December&nbsp;1941
}}
{{Infobox ship career
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|Ship struck=15 January 1942
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{{Infobox ship characteristics
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|Ship class= Type [[Japanese Type L submarine|L4 (''Ro-60''-class)]] submarine
|Ship displacement=*{{convert|988|long ton|t|lk=on}} (surfaced)
*1,301&nbsp;tons (1,322&nbsp;t) (submerged)
|Ship length={{convert|78.39|m|ftin|abbr=on}}
|Ship beam={{convert|7.41|m|ftin|abbr=on}}
|Ship draft={{convert|3.96|m|ftin|abbr=on}}
|Ship propulsion=*2 × Vickers diesels, 2 shafts<br> 2,400 bhp (surfaced), 1,600 (submerged)
|Ship speed=
*{{convert|15.7|kn|km/h}} (surfaced)
*{{convert|8.6|kn|km/h}} (submerged)
|Ship range=*{{convert|5,500|nmi|km}} at {{convert|10|kn|km/h}} (surfaced)
*{{convert|80|nmi|km}} at {{convert|5.7|kn|km/h}} (submerged)
|Ship endurance=
|Ship test depth={{convert|60|m|-1|abbr=on}}
|Ship complement=48
|Ship sensors=
|Ship EW=
|Ship fuel= 75 tons
|Ship armament=*6 × 533 mm torpedo tubes (6 × bow)
*12 × [[Imperial Japanese Navy Technical Department#6th Year Type Torpedo .281917.29|6th Year Type]] torpedoes
*1 × [[8 cm/40 3rd Year Type naval gun|76.2 mm (3.00 in)]] L/40 naval gun
*1 × 6.5 mm machine gun
|Ship notes=
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|}
'''''Ro-66''''' was an [[Imperial Japanese Navy]] [[Japanese Type L submarine|Type L]] [[submarine]] of the L4 subclass. First commissioned in 1927, she served in the waters of [[Japan]] prior to [[World War II]]. During World War II, she operated in the Central Pacific and supported Japanese forces in the [[Battle of Wake Island]] until she sank after a collision in December 1941.

==Design and description==
The submarines of the Type L4 sub-class were copies of the Group 3 subclass of the British [[British L-class submarine|L-class submarine]] built under license in Japan.<ref name=chesneau>Chesneau, Roger, ed., ''Conway′s All the World′s Fighting Ships 1922–1946'', New York: Mayflower Books, 1980, {{ISBN|0-8317-0303-2}}, p. 203.</ref> They were slightly larger and had two more [[torpedo tube]]s than the preceding submarines of the L3 subclass.<ref name=chesneau/> They [[Displacement (ship)|displaced]] {{Convert|988|LT|t|0|disp=flip}} surfaced and {{Convert|1,301|LT|t|0|disp=flip}} submerged. The submarines were {{convert|78.39|m|ftin|sp=us}} long and had a [[Beam (nautical)|beam]] of {{convert|7.41|m|ftin|sp=us}} and a [[Draft (hull)|draft]] of {{convert|3.96|m|ftin|sp=us}}. They had a diving depth of {{convert|60|m|ft|sp=us|0}}.

For surface running, the submarines were powered by two {{convert|1,200|bhp|lk=in|0|adj=on}} [[Vickers]] [[diesel engine]]s, each driving one [[propeller shaft]]. When submerged, each propeller was driven by an {{convert|800|shp|0|adj=on}} [[electric motor]]. They could reach {{convert|15.7|kn|lk=in}} on the surface and {{convert|8.6|kn}} underwater. On the surface, they had a range of {{convert|5,500|nmi|lk=in}} at {{convert|10|kn}}; submerged, they had a range of {{convert|80|nmi|abbr=on}} at {{convert|4|kn}}.

The submarines were armed with six internal {{convert|533|mm|in|abbr=on|sp=us|sigfig=2}} [[torpedo tube]]s, all in the [[Bow (ship)|bow]], and carried a total of twelve [[Imperial Japanese Navy Technical Department#6th Year Type Torpedo .281917.29|6th Year Type torpedoes]]. They were also armed with a single [[8 cm/40 3rd Year Type naval gun|{{convert|76.2|mm|in|abbr=on|0}}]] deck gun and a 6.5&nbsp;mm [[machine gun]].

==Construction and commissioning==

''Ro-66'' was [[Keel-laying|laid down]] on 1 December 1925 by [[Mitsubishi Heavy Industries|Mitsubishi]] at [[Kobe]], [[Japan]].<ref name=ijnsubsiteRo66>{{cite web |url= http://www.ijnsubsite.info/RO-Sub%20Details/RO-66.htm |title=RO-66 |work=iijnsubsite.info |year=2016|access-date=21 October 2020}}</ref><ref name=combinedfleetRo66>{{cite web |url= http://www.combinedfleet.com/RO-66.htm|title=Sensuikan: IJN Submarine RO-66: Tabular Record of Movement|first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017 |access-date=21 October 2020}}</ref> [[Ceremonial ship launching|Launched]] on 25 October 1926,<ref name=ijnsubsiteRo66/><ref name=combinedfleetRo66/> she was completed and [[Ship commissioning|commissioned]] on 28&nbsp;July&nbsp;1927.<ref name=ijnsubsiteRo66/><ref name=combinedfleetRo66/>

==Service history==
===Pre-World War II===

Upon commissioning, ''Ro-66'' was attached to the [[Sasebo Naval District]] and assigned to Submarine Division 27 — in which she spent her entire career — in Submarine [[Squadron (naval)|Squadron]] 1 in the [[1st Fleet (Imperial Japanese Navy)|1st Fleet]] in the [[Combined Fleet]].<ref name=ijnsubsiteRo66/><ref name=combinedfleetRo66/> Submarine Division 27 was reassigned to the Sasebo Defense Division in the Sasebo Naval District on 30 November 1929.<ref name=ijnsubsiteRo66/> On 24 December 1929, the division was reassigned to Submarine Squadron 2 in the [[2nd Fleet (Imperial Japanese Navy)|2nd Fleet]] in the Combined Fleet.<ref name=ijnsubsiteRo66/> ''Ro-66'' was [[Ship decommissioning|decommissioned]] and placed [[Reserve fleet|in reserve]] at [[Sasebo]], Japan, on 15 November 1930.<ref name=ijnsubsiteRo66/><ref name=combinedfleetRo66/>

''Ro-66'' was recommissioned on 1 May 1931,<ref name=ijnsubsiteRo66/> resuming active service in Submarine Division 27, which by then had been reassigned to the Sasebo Defense Division in the Sasebo Naval District.<ref name=ijnsubsiteRo66/> On 1 October 1932, the division was reassigned to the Sasebo Guard Squadron.<ref name=ijnsubsiteRo66/> On 15 November 1933, the division returned to service in the Sasebo Defense Division,<ref name=ijnsubsiteRo66/> and that day ''Ro-66'' again was decommissioned and placed in reserve at Sasebo.<ref name=ijnsubsiteRo66/><ref name=combinedfleetRo66/>

''Ro-66'' was recommissioned on 15 November 1934,<ref name=ijnsubsiteRo66/> and returned to service in Submarine Division 27 which by then again was serving in the Sasebo Guard Squadron in the Sasebo Naval District.<ref name=ijnsubsiteRo66/> The division was transferred to the Sasebo Defense Squadron on 15 November 1935.<ref name=ijnsubsiteRo66/>

Sources offer different accounts of ''Ro-66''′s status during 1938–1940, implying both that she was in full commission throughout those years<ref name=combinedfleetRo66/> and stating that she was out of commission and in reserve — in Second Reserve from 15 December 1938 to 15 November 1939 and then in First Reserve until 15 November 1940<ref name=ijnsubsiteRo66/> — in the Sasebo Naval District between December 1938 and November 1940.<ref name=ijnsubsiteRo66/> Whatever the case, she was back in active service in time for Submarine Division 27′s reassignment to Submarine Squadron 7 in the [[4th Fleet (Imperial Japanese Navy)|4th Fleet]] in the Combined Fleet on 15 November 1940.<ref name=ijnsubsiteRo66/>

When the Imperial Japanese Navy deployed for the upcoming [[Pacific War|conflict in the Pacific]], ''Ro-66'' was at [[Kwajalein]] in the [[Marshall Islands]] with the other submarines of Submarine Division 27, {{ship|Japanese submarine|Ro-65||2}} and {{ship|Japanese submarine|Ro-67||2}}.<ref name=combinedfleetRo66/> She received the message "Climb [[Yu Shan|Mount Niitaka]] 1208" ({{langx|ja|Niitakayama nobore 1208}}) from the Combined Fleet on 2 December 1941, indicating that war with the [[Allies of World War II|Allies]] would commence on 8 December 1941 [[Japan Standard Time|Japan time]],<ref name=combinedfleetRo66/> which was on 7 December 1941 on the other side of the [[International Date Line]] in [[Hawaii]], where Japanese plans called for the war to open with their [[attack on Pearl Harbor]].

===World War II===
====Battle of Wake Island====
On 6 December 1941, ''Ro-66'' got underway from Kwajalein with the commander of Submarine Squadron 27 embarked to conduct a reconnaissance of [[Wake Island]],<ref name=combinedfleetRo66/> which the Japanese planned to invade on 8 December 1941, the first day of the war on Wake Island′s side of the International Date Line. The [[Battle of Wake Island]] began on 8 December 1941, with ''Ro-65'', ''Ro-66'', and ''Ro-67'' patrolling in the area supporting Japanese forces attempting to seize the [[atoll]].<ref name=combinedfleetRo66/> [[United States Marine Corps]] forces defending Wake drove back the initial Japanese assault that day.<ref name=combinedfleetRo66/>

While the Japanese gathered reinforcements for a second and larger invasion of the island, Submarine Squadron 7 sent orders to all three submarines of Submarine Division 27 on 12 December 1941 directing them to return to Kwajalein.<ref name=combinedfleetRo66/> Accordingly, ''Ro-65'' and ''Ro-67'' headed back to Kwajalein, but a radio failure prevented ''Ro-66'' from receiving the orders despite three attempts by Submarine Squadron 7 to contact her.<ref name=combinedfleetRo66/> Consequently, she continued to patrol off Wake Island<ref name=combinedfleetRo66/> as the submarines of Submarine Division 26 — {{ship|Japanese submarine|Ro-60||2}}, {{ship|Japanese submarine|Ro-61||2}},and {{ship|Japanese submarine|Ro-62||2}} — arrived in the area to relieve the departing submarines.<ref>{{cite web |url= http://www.combinedfleet.com/RO-60.htm|title=Sensuikan: IJN Submarine RO-60: Tabular Record of Movement|first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017 |access-date=17 October 2020}}</ref><ref>{{cite web |url= http://www.combinedfleet.com/RO-61.htm|title=Sensuikan: IJN Submarine RO-61: Tabular Record of Movement|first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017 |access-date=17 October 2020}}</ref><ref name=combinedfleetRo62>{{cite web |url= http://www.combinedfleet.com/RO-62.htm|title=Sensuikan: IJN Submarine RO-62: Tabular Record of Movement|first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017 |access-date=17 October 2020}}</ref>

===Loss===

''Ro-66'' was on the surface {{convert|25|nmi}} southwest of Wake Island — bearing 252 degrees from the atoll — to recharge her [[Electric battery|batteries]] in a heavy [[squall]] in the predawn darkness of 17 December 1941 when her lookouts suddenly sighted ''Ro-62'', also on the surface and recharging batteries.<ref name=ijnsubsiteRo66/><ref name=combinedfleetRo66/><ref name=combinedfleetRo62/> Both submarines attempted to back off, but it was too late to avoid a collision, and ''Ro-62'' rammed ''Ro-66'' at 20:20 [[Japan Standard Time]].<ref name=combinedfleetRo66/><ref name=combinedfleetRo62/> ''Ro-66'' sank at {{coord|19|10|N|166|28|E|name=''Ro-66''}}<ref name=ijnsubsiteRo66/> with the loss of 63 lives, including that of the commander of Submarine Division 27.<ref name=ijnsubsiteRo66/><ref name=combinedfleetRo66/><ref name=combinedfleetRo62/> ''Ro-62'' rescued her three survivors, who had been thrown overboard from her [[Bridge (nautical)|bridge]] by the collision.<ref name=ijnsubsiteRo66/><ref name=combinedfleetRo66/><ref name=combinedfleetRo62/>

The Battle of Wake Island concluded on 23 December 1941 with the Japanese conquest of the atoll.<ref name=combinedfleetRo66/> The Japanese struck ''Ro-66'' from the Navy list on 15 January 1942.<ref name=combinedfleetRo66/>

==References==
{{reflist}}

==Bibliography==
*''{{cite web |url=http://rekigun.net/ |title=Rekishi Gunzō}}, History of Pacific War Extra, "Perfect guide, The submarines of the Imperial Japanese Forces"'', Gakken (Japan), March 2005, {{ISBN|4-05-603890-2}}
*''The Maru Special, Japanese Naval Vessels No.43 Japanese Submarines III'', Ushio Shobō (Japan), September 1980, Book code 68343-44
*''The Maru Special, Japanese Naval Vessels No.132 Japanese Submarines I "Revised edition"'', Ushio Shobō (Japan), February 1988, Book code 68344-36
*''The Maru Special, Japanese Naval Vessels No.133 Japanese Submarines II "Revised edition"'', Ushio Shobō (Japan), March 1988, Book code 68344-37

==External links==
* [http://www.combinedfleet.com/RO-66.htm Photo of ''Ro-66'' at combinedfleet.com]

{{Japanese Type L submarines|state=collapsed}}
{{December 1941 shipwrecks}}
{{Wake}}
{{authority control}}

{{DEFAULTSORT:Ro-066}}
[[Category:Ro-60-class submarines]]
[[Category:Japanese L type submarines]]
[[Category:Ships built by Mitsubishi Heavy Industries]]
[[Category:1926 ships]]
[[Category:World War II submarines of Japan]]
[[Category:Maritime incidents in November 1942]]
[[Category:Japanese submarine accidents]]
[[Category:Submarines sunk in collisions]]
[[Category:Japanese submarines lost during World War II]]
[[Category:World War II shipwrecks in the Pacific Ocean]]
[[Category:Battle of Wake Island]]