View source for Japanese submarine I-72

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{{Infobox ship career
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| Ship country=[[Empire of Japan]]
| Ship flag= {{shipboxflag|Empire of Japan|naval}}
| Ship name= ''I-72''
| Ship ordered=
| Ship awarded=
| Ship builder=[[Mitsubishi]] Kobe Yard, [[Kobe]],&nbsp;[[Japan]]
| Ship original cost=
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| Ship laid down=16 December 1933
| Ship launched=6 April 1935
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| Ship completed=7 January 1937
| Ship commissioned=7 January 1937
| Ship decommissioned=
| Ship out of service=
| Ship struck=15 December 1942
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| Ship renamed=''I-172'', 20 May 1942
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| Ship fate=Sunk October–November 1942 (see&nbsp;text)
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{{Infobox ship characteristics
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| Ship class = KD6 Type, [[Kaidai-type submarine|''Kadai'' type submarine]]
| Ship displacement = *1,400 (1,785 maximum) tons surfaced
* 2,440 tons submerged<ref name="Jentschura" />
| Ship length = {{convert|322|ft|10|in|m|abbr=on|1}}
| Ship beam = {{convert|26|ft|11|in|m|abbr=on|1}}
| Ship draught = {{convert|15|ft|0|in|m|abbr=on|1}}
| Ship propulsion = Twin shaft Kampon {{convert|9000|bhp|lk=in|abbr=on|0}}/two stroke diesels
| Ship speed = * {{convert|23|kn|lk=in}} diesel
* {{convert|8.2|kn}} electric<ref name="Jentschura">Jentschura p. 172</ref>
| Ship range = {{convert|14,000|nmi|abbr=on|lk=in}}<ref name="Jentschura" />
| Ship endurance = 
| Ship test depth = {{convert|230|ft|m|abbr=on}}
| Ship complement = 60–84 officers and enlisted
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| Ship armament = * 6 x [[torpedo tube]]s/14 {{convert|21|in|mm|abbr=on|0}} [[torpedo]]es
* 1 x [[10 cm/50 Type 88 naval gun|{{convert|100|mm|in|abbr=on}}]] [[Anti-aircraft warfare|AA]] gun
* 1 × [[Hotchkiss M1929 machine gun|{{convert|13.2|mm|in|abbr=on}}]] AA gun
|Ship notes=
}}
|}
'''''I-72''''', later '''''I-172''''', was a {{sclass2|Kaidai|submarine|0}} [[cruiser submarine]] of the KD6 [[ship class|sub-class]] built for the [[Imperial Japanese Navy]] (IJN) during the 1930s. She served in the early months of [[World War II]], supporting the [[attack on Pearl Harbor]], patrolling in Hawaiian waters in early 1942, and taking part in the [[Guadalcanal campaign]] before she was sunk in November 1942.

==Construction and commissioning==
Built by [[Mitsubishi]] at [[Kobe]], [[Japan]], ''I-72'' was [[Keel-laying|laid down]] on 16 December 1933 and [[Ceremonial ship launching|launched]] on 6 April 1935.<ref name=combinedfleetI72>{{cite web |url= http://www.combinedfleet.com/I-172.htm |title=IJN Submarine I-172: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2016|access-date=29 July 2020}}</ref> She was completed and accepted into Imperial Japanese Navy service on 7 January 1937.<ref name=combinedfleetI72/>

==Service history==
===Pre-World War II===
Upon commissioning, ''I-72'' was assigned to Submarine Division 20 in the [[Kure Naval District]]. While operating on the surface in limited visibility on 5 May 1938, she collided at about 10:00 with the Japanese 60-[[gross register ton]] [[motor vessel]] {{MV|Hachiyo Maru||2}} in the [[Seto Inland Sea]] west of [[Kurahashi-jima]], [[Japan]].<ref name=combinedfleetI72/> ''I-72'' suffered only minor damage, but ''Hachiyo Maru'' sank about two minutes after the collision.<ref name=combinedfleetI72/>

As the Imperial Japanese Navy began to deploy in preparation for the impending [[Pacific War|conflict]] in the [[Pacific Ocean|Pacific]], ''I-72'' departed [[Saeki District, Hiroshima|Seaki]], Japan, along with the submarines {{ship|Japanese submarine|I-68||2}}, {{ship|Japanese submarine|I-69||2}}, {{ship|Japanese submarine|I-70||2}}, {{ship|Japanese submarine|I-71||2}}, and {{ship|Japanese submarine|I-73||2}}.<ref name=combinedfleetI72/> She arrived at [[Kwajalein Atoll]] on 20 November 1941.<ref name=combinedfleetI72/>

===World War II===
====First war patrol====
On 23 November 1941, ''I-72'' departed Kwajalein to begin what would become her first war patrol.<ref name=combinedfleetI72/> 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 time (7 December 1941 in [[Hawaii]]).<ref name=combinedfleetI72/> She arrived in the Hawaiian Islands on 5 December 1941 and conducted a reconnaissance of [[Kalohi Channel]] between [[Lanai|Lānaʻi]] and [[Molokai|Molokaʻi]].<ref name=combinedfleetI72/> She then investigated [[Lahaina Roads]] off [[Maui]] to determine if the U.S. fleet was anchored there, and on 6 December 1941 she radioed the Japanese [[Kidō Butai|Carrier Striking Force]] with the news that no U.S. warships were at Lahaina Roads.<ref name=combinedfleetI72/>

On 7 December 1941, ''I-72'' took up station off [[Pearl Harbor]] between ''I-70'' and ''I-73''.<ref name=combinedfleetI72/> The Japanese [[attack on Pearl Harbor]] took place that morning, bringing Japan and the [[United States]] into [[World War II]]. On the evening of 16 December 1941, she surfaced off [[Hilo Bay]] and shelled [[Hilo, Hawaii|Hilo]], Hawaii, with her {{convert|4.7|in|mm|0|sigfig=2|adj=on}} deck gun.<ref name=combinedfleetI72/> On 19 December 1941, she [[torpedo]]ed the American 5,113-gross register ton [[Cargo ship|cargo]] [[Steamship|steamer]] {{SS|Prusa||2}} {{convert|150|nmi|0}} south of [[Oahu]].<ref name=combinedfleetI72/> ''Prusa'', which was on a voyage from [[Honolulu]], Hawaii, to [[Baltimore]], [[Maryland]], sank at {{coord|16|45|N|156|00|W|name=SS ''Prusa''}} nine minutes later.<ref name=combinedfleetI72/> ''I-72'' surfaced to identify ''Prusa'' and illuminated ''Prusa''′s [[Lifeboat (shipboard)|lifeboats]] with her [[searchlight]], then submerged and continued her patrol.<ref name=combinedfleetI72/> She returned to Kwajalein on 28 December 1941.<ref name=combinedfleetI72/>

====Second war patrol====
On 12 January 1942, ''I-72'' departed Kwajalein with ''I-71'' and ''I-73'' for her second war patrol.<ref name=combinedfleetI72/> This patrol also was in Hawaiian waters, where ''I-71'', ''I-72'', and ''I-73'' relieved the submarines {{ship|Japanese submarine|I-18||2}}, {{ship|Japanese submarine|I-22|1938|2}}, and {{ship|Japanese submarine|I-24|1939|2}} on a picket line.<ref name=combinedfleetI72/> ''I-72'' arrived in her patrol area on 21 January 1942.<ref name=combinedfleetI72/>

On 23 January, ''I-72'' encountered the 7,383-[[displacement ton]] [[United States Navy]] [[Replenishment oiler|oiler]] {{USS|Neches|AO-5}}, which was proceeding unescorted to a rendezvous with [[Task Force]] 11.<ref name=combinedfleetI72/> ''I-72''′s first torpedo, fired at 03:10, struck ''Neches'' amidships but failed to detonate.<ref name=combinedfleetI72/> Her second torpedo hit ''Neches'' on her starboard side aft, destroying her [[engine room]].<ref name=combinedfleetI72/> ''I-72''′s third torpedo struck ''Neches'' on her [[Port and starboard|port]] side.<ref name=combinedfleetI72/> When ''I-72'' surfaced to finish off ''Neches'' with her deck gun, ''Neches'' opened fire with {{convert|3|in|mm|1|adj=on}} and {{convert|5|in|mm|0|adj=on}} guns and forced the submarine to submerge again.<ref name=combinedfleetI72/> ''Neches'' then listed to starboard and sank by the [[Bow (ship)|bow]] at {{coord|21|01|N|160|06|W|name=USS ''Neches''}}.<ref name=combinedfleetI72/> The loss of ''Neches'' prevented Task Force 11 — centered around the [[aircraft carrier]] {{USS|Lexington|CV-2}} — from refueling, forcing it to cancel a planned air strike against Japanese forces on [[Wake Island]] and return to Pearl Harbor.<ref name=combinedfleetI72/>

On 16 February 1942, ''I-72'' returned to Kwajalein.<ref name=combinedfleetI72/>

====Third war patrol====

''I-72'' departed Kwajalein on 18 February 1942 with ''I-71'' to patrol in defense of [[Rabaul]], which the U.S. Navy's Task Force 11 was approaching with an intention to launch air raids against Japanese forces and bases there.<ref name=combinedfleetI72/> After Task Force 11 lost the element of surprise, however, it withdrew, and the two submarines were diverted to patrol areas east of Wake Island.<ref name=combinedfleetI72/> After an uneventful patrol, ''I-72'' proceeded to Japan, where she arrived on 5 March 1942 for repairs at [[Kure, Hiroshima|Kure]].<ref name=combinedfleetI72/>

====March–September 1942====
While ''I-72'' was at Kure, Submarine Division 20 was disbanded on 20 March 1942, and she was reassigned that day to Submarine Division 12.<ref name=combinedfleetI72/> She departed Kure on 15 April 1942, visited [[Yokosuka]] from 3 to 10 May 1942, and returned to Kure on 12 May 1942 for additional repairs.<ref name=combinedfleetI72/> While she was there, she was redesignated '''''I-172''''' on 20 May 1942.<ref name=combinedfleetI72/> With her repairs complete, she departed Kure on 22 August 1942 and proceeded to [[Chuuk Lagoon|Truk]], where she arrived on 28 August 1942.<ref name=combinedfleetI72/>

''I-172'' departed Truk on 30 August 1942.<ref name=combinedfleetI72/> The [[Guadalcanal campaign]] had begun on 7 August 1942, and her main task was to perform a reconnaissance mission in the [[Guadalcanal]] area.<ref name=combinedfleetI72/> She returned to Truk on 30 September 1942.<ref name=combinedfleetI72/>

====Fourth war patrol====
With the commander of Submarine Division 12 embarked, ''I-172'' departed Truk on 12 October 1942 for her fourth war patrol.<ref name=combinedfleetI72/> Her orders called for her to support an attack by [[Type A Kō-hyōteki-class submarine|Type A]] [[midget submarine]]s against Allied shipping off Guadalcanal's [[Lunga Point]].<ref name=combinedfleetI72/> On 14 October, however, she was ordered to proceed instead to join the submarine {{ship|Japanese submarine|I-26||2}} south of [[Makira|San Cristóbal]] to recharge the batteries of Type A midget submarines carried aboard the [[seaplane tender]] {{ship|Japanese aircraft carrier|Chiyoda||2}}.<ref name=combinedfleetI72/> Her orders again changed on 15 October 1942, when she was ordered to join the submarines {{ship|Japanese submarine|I-1||2}}, {{ship|Japanese submarine|I-2||2}}, {{ship|Japanese submarine|I-3||2}}, {{ship|Japanese submarine|I-4||2}}, {{ship|Japanese submarine|I-5||2}}, {{ship|Japanese submarine|I-7||2}}, {{ship|Japanese submarine|I-17||2}}, ''I-22'', and {{ship|Japanese submarine|I-31||2}} — collectively designated "Group A" — in forming a picket line southeast of Guadalcanal.<ref name=combinedfleetI72/> She remained on this duty through the end of the [[Battle of the Santa Cruz Islands]] of 25–27 October 1942.<ref name=combinedfleetI72/> Group A was dissolved on 28 October 1942,<ref name=combinedfleetI72/> and ''I-172'' then deployed to waters southwest of San Cristóbal with orders attack Allied shipping supplying American forces on Guadalcanal.<ref name=combinedfleetI72/>

====Loss====

Sources agree that ''I-172'' was sunk while operating southwest of San Cristóbal, but disagree on the date and cause.

A [[Naval History and Heritage Command]] document entitled "Appendix 3: Submarines Sunk by Patrol Squadrons During World War II" notes that the U.S. Navy [[destroyer minesweeper]] {{USS|Southard|DMS-10}} is given official credit for sinking ''I-172'' at the southern end of [[Indispensable Strait]] at {{coord|10|13|S|161|09|E|name=''I-172''}} on 10 November 1942 but adds that Japanese records indicate that ''Southard'' actually sank the Japanese submarine {{ship|Japanese submarine|I-15||2}}. The document claims that the Imperial Japanese Navy declared ''I-172'' missing after 28 October 1942 and attributes ''I-172''′s sinking to a U.S. Navy [[PBY-5 Catalina]] [[flying boat]] of [[VP-11|Patrol Squadron 11 (VP-11)]] that sighted a Japanese submarine on 29 October 1942 at {{coord|13|15|S|162|45|E|name=''I-172''}} and dropped two {{convert|650|lb|kg|0|adj=on}} [[depth charge]]s on it after it crash-dived. A large quantity of oil appeared on the surface and was still visible the next day.<ref>https://www.history.navy.mil/content/dam/nhhc/research/histories/naval-aviation/dictionary-of-american-naval-aviation-squadrons-volume-2/pdfs/Appen3.pdf {{Bare URL PDF|date=March 2022}}</ref>

According to [http://www.combinedfleet.com/kaigun.htm The Imperial Japanese Navy Page (combinedfleet.com)], on 3 November 1942 ''I-172'' sighted a convoy of American transports southwest of San Cristóbal bound for Lunga Point on Guadalcanal.<ref name=combinedfleetI72/> She transmitted her last message — a sighting report of seven transports steaming at {{convert|12|kn}} on a course of 300 degrees — at 04:10.<ref name=combinedfleetI72/> One of the convoy's escorts, the U.S. Navy [[light cruiser]] {{USS|Helena|CL-50}}, detected a surface target on [[radar]] bearing 046 true at a range of {{convert|16,000|yd|m|sigfig=3}} and the destroyer {{USS|McCalla|DD-488}} left the convoy at 05:20 to investigate.<ref name=combinedfleetI72/> ''McCalla'' sighted a nearly stationary submarine bearing 090 true at a range of {{convert|2,000|yd|m|sigfig=3}} and accelerated with an intention to ram the submarine.<ref name=combinedfleetI72/> The submarine submerged at 05:32 and turned sharply toward ''McCalla'', which sighted a [[periscope]] off her port bow at a range of {{convert|100|to|200|yd|m|sigfig=2}}.<ref name=combinedfleetI72/> ''McCalla'' began a [[depth charge]] attack at 05:37, dropping six {{convert|600|lb|kg|0|adj=on}} and five {{convert|300|lb|kg|0|adj=on}} depth charges set to explode at a depth of {{convert|50|to|100|ft|m|0}}.<ref name=combinedfleetI72/> Thirty seconds after the explosion of the last depth charge, ''McCalla''′s crew heard another underwater explosion, then a second explosion 30 seconds after that, and finally a third explosion after another three minutes.<ref name=combinedfleetI72/> After the third explosion, ''McCalla'' lost her [[sonar]] contact on the submarine, and her crew noticed a heavy smell of oil near {{coord|10|53|S|161|50|E|name=''I-172''}}.<ref name=combinedfleetI72/>

The ''[[Dictionary of American Naval Fighting Ships]]'' notes that ''McCalla'' conducted a depth charge attack on 2 November 1942, but makes no mention of ''McCalla'' sinking a submarine on either 2 or 3 November 1942.<ref>[https://www.history.navy.mil/research/histories/ship-histories/danfs/m/mccalla-ii.html Naval History and Heritage Command ''Dictionary of American Naval Fighting Ships'' McCalla II (DD-488)]</ref> It claims that early on the morning of 10 November 1942, while passing between San Cristobal and Guadalcanal en route to [[Aola Bay]] on Guadalcanal, ''Southard'' encountered ''I-172'' operating on the surface. ''Southard'' immediately slowed to {{convert|10|kn}} and opened fire. ''I-172'' submerged, and ''Southard'' commenced her first depth-charge attack. ''Southard'' lost contact with ''I-172'' and did not regain it again until 06:07, almost three and one-half hours later. Over the next three hours ''Southard'' made five more depth-charge runs. After the last barrage, she sighted oil on the surface. She moved in to investigate. Upon reaching the oil slick, ''Southard''{{'}}s crew could find no further evidence of damage, and she steamed on through the slick. When she reached a point about {{convert|2,000|yd|m|sigfig=3}} on the other side of the slick, the submarine surfaced almost vertically, exposing her whole [[conning tower]], her [[Hull (ship)|hull]] forward of the tower, and part of her [[keel]]. Then the bow dropped about 10 degrees, and the submarine sank rapidly by the stern. Though absolute confirmation of a kill was never received, all evidence strongly indicated that the submarine had indeed sunk.<ref>[https://www.history.navy.mil/research/histories/ship-histories/danfs/s/southard.html Naval History and Heritage Command ''Dictionary of American Naval Fighting Ships'' Southard (Destroyer No. 207)]</ref> Combinedfleet.com states that "Although USS ''Southard'' (DMS-10) is often credited with ''I-172''′s sinking, her target was more likely ''I-15''.<ref name=combinedfleetI72/>

On 27 November 1942, the Imperial Japanese Navy declared that ''I-172'' was presumed lost off Guadalcanal along with all 91 men on board.<ref name=combinedfleetI72/> She was struck from the Navy List 15 December 1942.<ref name=combinedfleetI72/>

==Notes==
{{Reflist}}

==References==
*{{cite web |url= http://www.combinedfleet.com/I-153.htm |title=IJN Submarine I-153: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2013|access-date=6 November 2015}}
*{{cite book| last = Jentschura| first = Hansgeorg| first2 = Dieter |last2=Jung|first3=Peter |last3=Mickel| year = 1977| title = Warships of the Imperial Japanese Navy, 1869&ndash;1945| publisher = United States Naval Institute| location = Annapolis, Maryland| isbn = 0-87021-893-X|name-list-style=amp}}

{{Kaidai type submarine}}
{{1938 shipwrecks}}
{{1942 shipwrecks}}

{{DEFAULTSORT:I-72}}
[[Category:1935 ships]]
[[Category:Ships built by Mitsubishi Heavy Industries]]
[[Category:World War II submarines of Japan]]
[[Category:Kaidai-class submarines]]
[[Category:Maritime incidents in 1938]]
[[Category:Maritime incidents in November 1942]]
[[Category:Attack on Pearl Harbor]]
[[Category:World War II shipwrecks in the Pacific Ocean]]
[[Category:Japanese submarines lost during World War II]]
[[Category:Missing submarines of World War II]]
[[Category:Warships lost in combat with all hands]]
[[Category:Submarines lost with all hands]]