View source for Japanese submarine I-7

{{Short description|Imperial Japanese Navy J3 type submarine}}
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{{Infobox ship image
|Ship image=File:Japanese submarine I-7 in 1937.jpg
|Ship caption=''I-7'' on her commissioning day, 31&nbsp;March&nbsp;1937.
}}
{{Infobox ship career
|Hide header=
|Ship country=[[Imperial Japanese Navy]]
|Ship flag=[[Image:Naval Ensign of Japan.svg|45px|RN Ensign]]
|Ship name=''I-7''
|Ship namesake=
|Ship ordered=1934
|Ship builder=[[Kure Naval Arsenal]], [[Kure, Hiroshima|Kure]],&nbsp;[[Japan]]
|Ship laid down=12 September 1934
|Ship launched=3 July 1935
|Ship completed=31 March 1937
|Ship acquired=
|Ship commissioned=31 March 1937
|Ship recommissioned=
|Ship decommissioned=
|Ship in service=
|Ship out of service=
|Ship struck=
|Ship reinstated=
|Ship honours=
|Ship fate=Wrecked 22 June 1943
}}
{{Infobox ship career
|Hide header=yes
|Ship struck=20 August 1943
|Ship honours=
|Ship notes=
}}
{{Infobox ship characteristics
|Hide header=
|Header caption=
|Ship class=[[Junsen type submarine|J3 type]] [[submarine]]
|Ship displacement=*2,231 tons (surfaced)
*3,583 tons(submerged)
|Ship length={{convert|109.30|m|ftin|abbr=on}}
|Ship beam={{convert|9.10|m|ftin|abbr=on}}
|Ship draft={{convert|5.26|m|ftin|abbr=on}}
|Ship depth={{convert|7.70|m|ftin|abbr=on}}
|Ship propulsion=*2 × [[Imperial Japanese Navy Technical Department|Kampon]] Mk.1A Model 10 [[diesel engine]]s, 11,200 [[Brake horsepower|bhp]] (9,472 [[Kilowatt|kW]])
*Two electric motors, 2,800 [[Shaft horsepower|shp]] (2,368&nbsp;kW)
*Two shafts
|Ship speed=*{{convert|23|kn|abbr=on}} (surfaced)
*{{convert|8|kn|abbr=on}} (submerged)
|Ship range=*{{convert|14,000|nmi|abbr=on}} at {{convert|16|kn|abbr=on}} (surfaced)
*{{convert|80|nmi|abbr=on}} at {{convert|3|kn|abbr=on}} (submerged)
|Ship test depth={{convert|100|m|ft|0|abbr=on}}
|Ship complement=100 officers and men
|Ship sensors=
|Ship EW=
|Ship armament=*6 × {{convert|533|mm|in|adj=on|abbr=on|0}} [[torpedo tube]]s (6&nbsp;bow)
*20 × [[Type 89 torpedo|Type 89]] [[torpedo]]es
*2 × [[14 cm/40 11th Year Type naval gun|{{convert|140|mm|in|abbr=on|adj=on|1}}/40 cal 11th Year-Type guns]]
*2 × {{convert|13.2|mm|in|adj=on|abbr=on|1}} [[machine gun]]s
|Ship armour=
|Ship armor=
|Ship aircraft=1 × [[Watanabe E9W]]1
|Ship aircraft facilities=[[Hangar]], [[Aircraft catapult|catapult]]
|Ship notes=
}}
|}
'''''I-7''''' was an [[Imperial Japanese Navy]] [[Junsen type submarine|J3 type]]  [[submarine]] commissioned in 1937. She was a large [[cruiser submarine]] that served in [[World War II]]. She operated in support of the [[attack on Pearl Harbor]], conducted anti-shipping patrols in the [[Indian Ocean]], supported the [[Indian Ocean raid]], and took part in the [[Guadalcanal campaign]] and the [[Aleutian Islands campaign]]. She was wrecked in the [[Aleutian Islands]] after a lengthy battle with the [[destroyer]] {{USS|Monaghan|DD-354}} in June 1943.

== Design, construction, and commissioning ==
''I-7'' was the first of two ''Junsen III''- (or "J3"-) type submarines. After the four ''Junsen I''-type submarines ({{ship|Japanese submarine|I-1||2}}, {{ship|Japanese submarine|I-2||2}}, {{ship|Japanese submarine|I-3||2}}, and {{ship|Japanese submarine|I-4||2}}), the Japanese had built {{ship|Japanese submarine|I-5||2}} as a modified ''Junsen I'', introducing an aviation capability to the ''Junsen'' type with the inclusion of a [[hangar]] that allowed ''I-5'' to carry and operate a [[floatplane]]. ''I-6'', the only ''Junsen II''-type submarine, represented the next step in the evolution of this aviation capability, as she had both a hangar and a [[Aircraft catapult|catapult]] for a floatplane. The Japanese designed and equipped the next and last ''Junsen'' type submarines, ''I-7'' and {{ship|Japanese submarine|I-8||2}} — the only two ''Junsen III''-type submarines — to operate as submarine [[Squadron (naval)|squadron]] [[flagship]]s.<ref>Boyd and Yoshida, p. 22.</ref> In them, the Japanese sought to combine what they viewed as the best features of the earlier ''Junsen''-type submarines with those of the [[Kaidai-type submarine|Kaidai V-type]] submarines. Like ''I-6'' before them, ''I-7'' and ''I-8'' had a hangar and catapult for a floatplane. They were the last Japanese submarines with aircraft facilities abaft the [[conning tower]]; all later Japanese submarines with aircraft capabilities had their hangars and catapults on their forward decks.<ref>Boyd and Yoshida, p. 23.</ref>

Built by the [[Kure Naval Arsenal]] at [[Kure, Hiroshima|Kure]], [[Japan]], ''I-7'' was [[Keel-laying|laid down]] on 12 September 1934.<ref name=ijnsubsiteI7>[http://www.ijnsubsite.info/I-Sub%20Details/I-7.htm I-7 ijnsubsite.com 23 June 2018 Accessed 29 January 2022]</ref><ref name=combinedfleetI7>{{cite web |url= http://www.combinedfleet.com/I-7.htm |title=IJN Submarine I-7: Tabular Record of Movement |first1=Bob |last1=Hackett |first2=Sander |last2=Kingsepp |work=combinedfleet.com |year=2017|access-date=13 August 2020}}</ref> She was [[Ceremonial ship launching|launched]] on 3 July 1935<ref name=ijnsubsiteI7/><ref name=combinedfleetI7/> and was completed and [[Ship commissioning|commissioned]] on 31 March 1937.<ref name=ijnsubsiteI7/><ref name=combinedfleetI7/>

== Service history ==
=== Pre-World War II ===
Upon commissioning, ''I-7'' was attached to the [[Yokosuka Naval District]].<ref name=ijnsubsiteI7/><ref name=combinedfleetI7/> On 1 December 1937, she became [[flagship]] of Submarine [[Squadron (naval)|Squadron]] 1 in the [[1st Fleet (Imperial Japanese Navy)|1st Fleet]], a component of the [[Combined Fleet]].<ref name=ijnsubsiteI7/> She became flagship of Submarine Squadron 4 in the 1st Fleet on 15 November 1939,<ref name=ijnsubsiteI7/> and on 11 October 1940 she was one of 98 Imperial Japanese Navy ships that gathered along with more than 500 aircraft on the Japanese coast at [[Yokohama Bay]] for an [[Fleet Review (Japan)|Imperial fleet review]] — the largest [[fleet review]] in Japanese history — in honor of the 2,600th anniversary of the enthronement of the [[Emperor Jimmu]], Japan's legendary first [[Emperor of Japan|emperor]].<ref name=ijnsubsiteI7/><ref name="combinedfleetchitoseavp"/><ref>{{cite news |title=2012 Fleet Review |url=https://www.mod.go.jp/e/jdf/pdf/jdf_no35.pdf |accessdate=October 8, 2019 |work=Japan Defense Focus |date=December 2012}}</ref>

''I-7'' became flagship of Submarine Squadron 2 in the [[6th Fleet (Imperial Japanese Navy)|6th Fleet]], a component of the Combined Fleet, on 15 November 1940.<ref name=combinedfleetchitoseavp>{{cite web |url= http://www.combinedfleet.com/chitosesp_t.htm |title=IJN Seaplane Carrier CHITOSE: Tabular Record of Movement |first1=Athony |last1=Tully |work=combinedfleet.com |date=19 May 2014|access-date=11 December 2021}}</ref><ref name=combinedfleetI7/> While taking part in maneuvers in [[Saeki Bay]] on the morning of 21 October 1941, she collided with the submarine ''[[Japanese submarine I-166|I-66]]''.<ref name=ijnsubsiteI7/><ref name=combinedfleetI7/> Both submarines suffered light damage.<ref name=combinedfleetI7/>

On 10 November 1941 — by which time  ''I-7'' was serving in the 6th Fleet as [[flagship]] of Submarine Squadron 2 and was assigned to Submarine Division 8 with the submarines {{ship|Japanese submarine|I-4||2}}, {{ship|Japanese submarine|I-5||2}}, and {{ship|Japanese submarine|I-6||2}}.<ref name=combinedfleetI7/> — the commander of the 6th Fleet, [[Vice Admiral]] [[Mitsumi Shimizu]], gathered the [[commanding officer]]s of the fleet's submarines together for a meeting aboard his [[flagship]], the light cruiser {{ship|Japanese cruiser|Katori||2}}, which was anchored in Saeki Bay.<ref name=combinedfleetI7/> His chief of staff briefed them on the upcoming [[attack on Pearl Harbor]], which would bring Japan and the [[United States]] into [[World War II]].<ref name=combinedfleetI7/> On 11 November 1941, ''I-7'' was reassigned to the Submarine Advance Force.<ref name=combinedfleetI7/>

As the Imperial Japanese Navy began to deploy on 16 November 1941 for the upcoming [[Pacific War|conflict in the Pacific]], ''I-7'' embarked both the commander of Submarine Squadron 2 and a [[Watanabe E9W]]1 ([[World War II Allied names for Japanese aircraft|Allied reporting name]] "Slim") [[reconnaissance seaplane]].<ref name=combinedfleetI7/> At 13:00 that day, ''I-4'', ''I-5'', ''I-6'', and ''I-7'' got underway from [[Yokosuka]] bound for the [[Hawaiian Islands]].<ref name=combinedfleetI7/> While {{convert|300|nmi}} north of [[Oahu]], ''I-7'' 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]], which was on 7 December 1941 on the other side of the [[International Date Line]] in [[Hawaii]].<ref name=combinedfleetI7/>

=== World War II ===
==== First war patrol ====
On 7 December 1941, the submarines of Submarine Squadron 2 took up patrol stations across a stretch of the [[Pacific Ocean]] from northeast to northwest of [[Oahu]], with ''I-7'' operating as their flagship.<ref name=combinedfleetI7/> The submarines had orders to conduct reconnaissance in the area and attack any ships which [[sortie]]d from [[Pearl Harbor]] during or after the attack, which occurred that morning.<ref name=combinedfleetI7/> On 10 December 1941, ''Katori'' transmitted a message from Shimizu to the squadron commander ordering ''I-7''′s floatplane to conduct a reconnaissance flight over [[Pearl Harbor]] to report on damage inflicted during the attack three days earlier and the progress the Americans were making on repairs.<ref name=combinedfleetI7/> Accordingly, ''I-7'' launched her floatplane early on the morning of 16 December 1941 from a position {{convert|26|nmi}} west of [[Kailua-Kona, Hawaii|Kailua-Kona]] on the island of [[Hawaii (island)|Hawaii]].<ref name=combinedfleetI7/> At 07:10, the floatplane's [[Air observer|observer]] reported four [[battleship]]s — one of them heavily damaged — and an [[aircraft carrier]] in Pearl Harbor off the East Loch anchorage and five [[cruiser]]s and 30 smaller vessels including three [[destroyer]]s in the harbor south of [[Ford Island]].<ref name=combinedfleetI7/> The floatplane returned to ''I-7'' and landed next to her at 09:45 and, after its two-man crew abandoned the plane and swam to the submarine, ''I-7'' [[Scuttling|scuttled]] the plane, submerged, and left the area.<ref name=combinedfleetI7/>

On 17 December 1941, ''I-7'' received orders to move to an operating area southwest of Oahu to support a sweep line by Submarine Squadron 2.<ref name=combinedfleetI7/> Detached from that duty on 21 December 1941, she shifted to a patrol area southeast of Oahu.<ref name=combinedfleetI7/> While {{convert|120|nmi}} southeast of Oahu on 1 January 1942, ''I-7'' sighted a light cruiser and two destroyers steaming toward Pearl Harbor and fired two [[torpedo]]es at them, both of which missed.<ref name=combinedfleetI7/> The destroyers counterattacked, dropping six [[depth charge]]s, but ''I-7'' escaped unscathed.<ref name=combinedfleetI7/> On 9 January 1942, the submarine {{ship|Japanese submarine|I-18||2}} reported sighting the aircraft carrier {{USS|Lexington|CV-2}} northeast of [[Johnston Island]], and ''I-7'' diverted from her patrol to take part in the hunt for ''Lexington'', but failed to find her.<ref name=combinedfleetI7/> She then headed for [[Kwajalein]], which she reached on 22 January 1942.<ref name=combinedfleetI7/> She got back underway on 24 January 1942 bound for Yokosuka, which she reached on 2 February 1942.<ref name=combinedfleetI7/>

==== Second war patrol ====
While ''I-7'' was at Yokosuka, Submarine Squadron 2 — consisting of ''I-1'', ''I-2'', ''I-3'', ''I-4'', ''I-5'',  ''I-6'', and ''I-7'' — was assigned to the [[Dutch East Indies campaign|Dutch East Indies Invasion]] Force in the Southeast Area Force on 8 February 1942, operating as Submarine Group C with ''I-7'' designated the group's flagship.<ref name=combinedfleetI7/> ''I-7'' departed Yokosuka on 11 February 1942 bound for [[Palau]], which she reached on 16 February, then got back underway on 17 February 1942 for the [[Netherlands East Indies]].<ref name=combinedfleetI7/> She arrived at [[Staring Bay]] on the [[Southeast Peninsula, Sulawesi|Southeast Peninsula]] of [[Celebes]] just southeast of [[Kendari]] on 21 February 1942.<ref name=combinedfleetI7/> At 06:00 local time on 23 February 1942, she began her second war patrol with the commander of Submarine Group C embarked, bound for a patrol area in the [[Indian Ocean]] south of [[Java]].<ref name=combinedfleetI7/>  ''I-4'', ''I-5'', ''I-6'', and ''I-7'' formed a sweep line {{convert|400|nmi}} south of Java to interdict [[Allies of World War II|Allied]] shipping between Java and [[Australia]], after which Submarine Group C patrolled south of the [[Cocos (Keeling) Islands]].<ref name=combinedfleetI7/>

At 12:30 on 2 March 1942, ''I-7'' was operating in the Indian Ocean {{convert|150|nmi}} southwest of the Cocos Islands when an unidentified Japanese carrier aircraft attacked her by mistake.<ref name=combinedfleetI7/> She suffered no damage.<ref name=combinedfleetI7/> At 10:00 on 4 March 1942, she surfaced in the Indian Ocean {{convert|250|nmi}} northwest of the Cocos Islands and opened fire with her deck guns on the [[Netherlands|Dutch]] 865-ton [[motor vessel]] {{MV|Merkus||2}}, a [[merchant ship]] on a voyage from [[Tjilatjap]], Java, to [[Colombo]], [[Ceylon]], with a cargo of [[rubber]].<ref name=combinedfleetI7/> ''Merkus''′s crew abandoned ship without loss of life, after which ''I-7'' sank the ship with gunfire at {{coord|08|40|S|094|30|E|name=MV ''Merkus''}}.<ref name=combinedfleetI7/> She concluded her patrol with her arrival at [[Penang Island|Penang]] in Japanese-occupied [[British Malaya]] on 8 March 1942.<ref name=combinedfleetI7/>

==== Indian Ocean raid ====
Orders arrived from the [[Headquarters unit|headquarters]] of the [[Combined Fleet]] for all the submarines of Submarine Squadron 2 except for ''I-1'' to conduct reconnaissance operations along the coast of [[Ceylon]] and western coast of [[India]] in preparation for Operation C, the upcoming [[Indian Ocean raid]] by the aircraft carriers of the Combined Fleet's [[Kido Butai|Mobile Force]].<ref name=combinedfleetI7/> Accordingly, ''I-7'' departed Penang at 16:00 local time on 28 March 1942 with a Watanabe E9W1 (Allied reporting name "Slim") floatplane embarked.<ref name=combinedfleetI7/> She was tasked to use the aircraft to conduct a reconnaissance of Colombo and [[Trincomalee]], Ceylon, on 3 April 1942, two days before the scheduled Japanese carrier air strikes there.<ref name=combinedfleetI7/>

At 05:17 on 1 April 1942, a [[Royal Air Force]] [[PBY Catalina|Catalina I]] [[flying boat]], probably from [[No. 201 Squadron RAF|No. 201 Squadron]], attacked ''I-7'' while she was on the surface in the Indian Ocean {{convert|180|nmi}} southeast of Ceylon.<ref name=combinedfleetI7/> The Catalina dropped two bombs which landed close aboard, but ''I-7'' suffered no damage.<ref name=combinedfleetI7/> Four hours later she encountered several small Allied [[patrol vessel]]s in the same area, and her commanding officer decided to cancel the reconnaissance flight scheduled for 3 April because of the enemy activity in the launch area.<ref name=combinedfleetI7/> Instead, ''I-7'' provided [[Meteorology|weather reports]] to the approaching Mobile Force.<ref name=combinedfleetI7/>

At 03:40 on 3 April 1942, ''I-7'' attacked the [[United Kingdom|British]] 9,415-ton motor vessel {{MV|Glenshiel||2}} in the Indian Ocean {{convert|300|nmi}} east of the [[Maldive Islands]].<ref name=combinedfleetI7/> ''I-7'' fired two [[Type 89 torpedo]]es at ''Glenshiel'', which was on a voyage from [[Bombay]], India, to [[Fremantle]], Australia, carrying 12 passengers and 1,000 tons of general cargo.<ref name=combinedfleetI7/> One torpedo hit ''Glenshiel'' on her [[Port and starboard|port]] side, and she began to settle by the [[stern]].<ref name=combinedfleetI7/> ''Glenshiel'' transmitted a [[distress signal]] and her crew and passengers — all of whom survived — abandoned ship.<ref name=combinedfleetI7/> After waiting for the [[Lifeboat (shipboard)|lifeboats]] to clear the ship, ''I-7'' fired two more torpedoes, one of which hit.<ref name=combinedfleetI7/> She then surfaced and opened fire on the ship with her deck guns, scoring 20 [[Shell (projectile)|shell]] hits before the burning ''Glenshiel'' sank by the stern at {{coord|00|48|S|078|33|E|name=MV ''Glenshiel''}}.<ref name=combinedfleetI7/>

Reassigned to the Advance Force on 10 April 1942,<ref name=combinedfleetI7/> ''I-7'' arrived at [[Singapore]] along with ''I-3'' on 15 April 1942.<ref name=combinedfleetI7/> She got back underway on 21 April 1942 and arrived at Yokosuka on 1 May 1942 to undergo repairs.<ref name=combinedfleetI7/>

==== Third war patrol ====

While ''I-7'' was at Yokosuka, the [[Aleutian Islands campaign]] began on 3–4 June 1942 with a [[Battle of Dutch Harbor|Japanese air raid]] on [[Dutch Harbor]], [[Territory of Alaska|Alaska]], followed quickly by the unopposed Japanese occupation in the [[Aleutian Islands]] of [[Attu Island|Attu]] on 5 June and [[Kiska]] on 7 June 1942.<ref name=combinedfleetI7/> On 10 June 1942, ''I-1'', ''I-2'', ''I-3'', ''I-4'', ''I-5'', ''I-6'', and ''I-7'' were reassigned to the Northern Force for duty in the Aleutians, and on 11 June 1942 ''I-7'' set out for Aleutian waters to begin her third war patrol.<ref name=combinedfleetI7/> She joined the "K" patrol line and patrolled off [[Unalaska Island]].<ref name=combinedfleetI7/> She was in the [[Gulf of Alaska]] on 14 July 1942 when she torpedoed the 2,722-ton [[United States Army Transport]] {{USAT|Arcata}}, which was on a voyage from [[Bethel, Alaska|Bethel]], Alaska, to [[Seattle]], [[Washington (state)|Washington]].<ref name=combinedfleetI7/><ref name=wrecksitearcata>[https://www.wrecksite.eu/wreck.aspx?32245 wrecksite.eu SS Arcata (+1942)]</ref> She then attacked ''Arcata'' with gunfire, her gun crew finding accuracy difficult in the choppy seas.<ref name=combinedfleetI7/> After one of ''I-7''′s shells hit ''Arcata''′s [[Bridge (nautical)|bridge]], her passengers and crew abandoned ship.<ref name=combinedfleetI7/> Seven members of ''Arcata''′s crew were killed.<ref name=wrecksitearcata/> Japanese records claim ''I-7'' ceased fire when she spotted [[life raft]]s in the water,<ref name=combinedfleetI7/><ref name=wrecksitearcata/> while ''Arcata''′s survivors reported that ''I-7'' machine-gunned the life rafts, killing one crewman.<ref name=wrecksitearcata/> ''Arcata'' sank at {{coord|53|41|N|157|45|W|name=USAT ''Arcata''}}.<ref name=combinedfleetI7/>

''I-7'' was assigned to the Advance Force on 20 July 1942.<ref name=combinedfleetI7/> Her patrol ended with her arrival on 1 August 1942 at Yokosuka, where she began an overhaul.<ref name=combinedfleetI7/>

==== Fourth war patrol ====
During ''I-7''′s stay at Yokosuka, the [[Guadalcanal campaign]] began on 7 August 1942 with U.S. amphibious landings on [[Guadalcanal]], [[Tulagi]], [[Florida Island]], [[Gavutu]], and [[Tanambogo]] in the southeastern [[Solomon Islands (archipelago)|Solomon Islands]].<ref name=combinedfleetI7/> On 20 August 1942, Submarine Squadron 2 was disbanded and ''I-7'' was assigned directly to 6th Fleet [[Headquarters unit|headquarters]].<ref name=combinedfleetI7/> She was again reassigned, to Submarine Division 7, on 31 August 1942.<ref name=combinedfleetI7/> With the commander of Submarine Division 7 and a Watanabe E9W1 (Allied reporting name "Slim") floatplane embarked, she departed Yokosuka on 8 September 1942 bound for [[Chuuk Lagoon|Truk]], which she reached on 15 September 1942.<ref name=combinedfleetI7/> Upon arrival there, she was assigned to the 1st Picket Unit.<ref name=combinedfleetI7/> With the commander of Submarine Division 7 still aboard, she got back underway on 19 September 1942 to begin her fourth war patrol, assigned a patrol line southeast of [[Makira|San Cristobal]] in the Solomon Islands.<ref name=combinedfleetI7/>

On 10 October 1942, ''I-7'' was diverted from her patrol to conduct a reconnaissance of [[Espiritu Santo]] prior to a planned raid there by a Special Landing Unit put ashore by ''I-1''.<ref name=combinedfleetI7/> On 13 October 1942, her floatplane made a reconnaissance flight over Espiritu Santo, reporting two light cruisers, seven [[Transport (ship)|transports]], several smaller vessels, and [[seaplane]]s off the island's south coast.<ref name=combinedfleetI7/> ''I-7'' bombarded Espiritu Santo after dark on 14 October 1942, firing fourteen {{convert|140|mm|in|adj=on|sp=us|1}} rounds.<ref name=combinedfleetI7/> Before sunrise on 23 October 1942 she again bombarded the island, but fired only six rounds before return fire by [[coastal artillery]] forced her to submerge.<ref name=combinedfleetI7/>

On 24 October 1942 ''I-7'' was ordered to return to rejoin the "A" patrol group southeast of Guadalcanal, but she again received orders on 31 October 1942 to launch a reconnaissance flight over Espiritu Santo.<ref name=combinedfleetI7/> Her floatplane was damaged and could not carry out the flight,<ref name=combinedfleetI7/> but ''I-7'' did conduct a [[periscope]] reconnaissance of Espiritu Santo on 7 November 1942.<ref name=combinedfleetI7/> After the submarine {{ship|Japanese submarine|I-9||2}}, carrying a [[Yokosuka E14Y]]1 (Allied reporting name "Glen") floatplane, relieved her off Espiritu Santo, ''I-7'' received orders on 9 November 1942 to reconnoiter [[Ndeni]] and [[Vanikoro]] in the [[Santa Cruz Islands]].<ref name=combinedfleetI7/> She conducted a periscope reconnaissance of Ndeni on 10 November 1942, finding nothing important, and her floatplane made a reconnaissance flight over Vanikoro on 11 November 1942.<ref name=combinedfleetI7/> She then proceeded to Truk, which she reached on 18 November 1942.<ref name=combinedfleetI7/>

''I-7'' departed Truk on 24 November 1942.<ref name=combinedfleetI7/> On 1 December 1942, she arrived at Yokosuka for an extended stay.<ref name=combinedfleetI7/>

==== Aleutian Islands campaign ====
On 1 April 1943, Submarine Division 7 was reassigned to the [[5th Fleet (Imperial Japanese Navy)|5th Fleet]] for service in the North Pacific.<ref name=combinedfleetI7/> Tasked with running supplies and reinforcements to the isolated Japanese garrisons on Attu and Kiska in the Aleutian Islands, ''I-7'' departed Yokosuka on 21 April 1943 with a cargo of food and ammunition bound for Kiska.<ref name=combinedfleetI7/> She called at Kiska on 1 May 1943, unloaded her cargo, and got underway the same day for Attu, which she reached on 4 May 1943.<ref name=combinedfleetI7/> Leaving Attu the same day, she stopped briefly at [[Paramushiro]] in the [[Kuril Islands]] on 8 May 1943, then proceeded to Yokosuka, arriving there on 12 May 1943.<ref name=combinedfleetI7/> During her voyage, U.S. forces landed on Attu on 11 May 1943, beginning the [[Battle of Attu]].<ref name=combinedfleetI7/>

With the commander of Submarine Division 7 embarked, ''I-7'' departed Yokosuka on 18 May 1943 both to carry supplies to the Japanese forces fighting on Attu and conduct her fifth war patrol.<ref name=combinedfleetI7/> By the time she arrived in the Attu area on 21 May 1943, the situation on Attu had deteriorated to the point that the Japanese [[Imperial General Headquarters]] decided to abandon the garrison on Attu — which American forces eventually annihilated, securing the island on 30 May 1943 — and evacuate the isolated garrison on Kiska by submarine, with the evacuation to begin on 26 May 1943.<ref name=combinedfleetI7/> On 24 May 1943, ''I-7'' departed her patrol area off Attu to head for Kiska, and she received orders on 25 May 1943 confirming that decision.<ref name=combinedfleetI7/> When she arrived off Kiska on 26 May 1943, she found the harbor under air attack.<ref name=combinedfleetI7/> She waited at sea until 22:30, then entered the harbor and discharged a cargo of six tons of food, 13.2-mm, 8-mm, and 7.7-mm ammunition, and a [[radio beacon]].<ref name=combinedfleetI7/> After embarking 60 mostly sick and wounded passengers — 49 naval personnel, seven [[Imperial Japanese Army]] personnel, and four paramilitary workers — as well as 28 boxes containing the [[Cremation|cremated remains]] of soldiers and four tons of spent shell [[Cartridge (firearms)|cartridges]], she put back to sea at 01:00 on 27 May 1943 and headed for Paramushiro, arriving there on 1 June 1943.<ref name=combinedfleetI7/> The [[Oiler (ship)|oiler]] {{ship||Teiyō Maru|1931|2}} refueled ''I-7'' and the submarines {{ship|Japanese submarine|I-21||2}}, {{ship|Japanese submarine|I-155||2}}, {{ship|Japanese submarine|I-156||2}}, and {{ship|Japanese submarine|I-157||2}} on 2 June 1943.<ref name=combinedfleetI7/>

On 4 June 1943, ''I-7'' got underway from Paramushiro for another supply run to Kiska.<ref name=combinedfleetI7/> Calling there on 8 June 1943 along with the submarine {{ship|Japanese submarine|I-34||2}}, she unloaded nine tons of ammunition and 15 tons of food, embarked 101 passengers — 42 naval personnel, 18 army personnel, and 41 paramilitary workers — and began her return to Paramushiro, which she reached on 13 June 1943.<ref name=combinedfleetI7/>

''I-7'' once again embarked the commander of Submarine Division 7 for her next supply run, leaving Paramushiro at 16:00 on 15 June 1943.<ref name=combinedfleetI7/> While she was at sea on 17 June, the commander of Submarine Squadron 1 issued a directive ordering ''I-7'', ''I-34'', and the submarines {{ship|Japanese submarine|I-36||2}} and {{ship|Japanese submarine|I-169||2}} to suspend their supply runs to Kiska and await further orders because of the grounding on 16 June 1943 of ''I-157'' and recent attacks on Japanese submarines in the Aleutians by [[radar]]-equipped American destroyers.<ref name=combinedfleetI7/> Submarine Squadron 1 directed ''I-2'', ''I-157'', and the submarine {{ship|Japanese submarine|I-175||2}} to determine the locations of the American ships.<ref name=combinedfleetI7/>

Under pressure from higher command to continue the supply and evacuation of Kiska,<ref>Boyd and Yoshida, pp. 118–119.</ref> Submarine Squadron 1 reversed its decision on 18 June 1943 and ordered the resumption of the submarine supply runs.<ref name=combinedfleetI7/> On 19 June 1943, ''I-7'' arrived off Kiska, but found Gertrude Cove in Vega Bay shrouded in dense [[fog]].<ref name=combinedfleetI7/> Her commanding officer decided to delay her attempt to land her cargo.<ref name=combinedfleetI7/>

==== Loss ====
''I-7'' surfaced off Kiska approximately {{convert|1|nmi}} south of Vega Bay in heavy fog at 19:00 on 20 June 1943 and began an attempt to enter the anchorage at Gertrude Cove.<ref name=combinedfleetI7/> The destroyer {{USS|Monaghan|DD-354}}, patrolling {{convert|2|nmi}} off [[Bukhti Point]], detected ''I-7'' on radar at a range of {{convert|14,000|yd|m|sigfig=3}} and began to close the range.<ref name=combinedfleetI7/> ''I-7'' lacked radar<ref name=Boydyoshidap119>Boyd and Yoshida, p. 119.</ref> and was unaware that ''Monaghan'' was in the vicinity until 19:20, when her sound operator reported hearing [[propeller]] noises to starboard, and ''I-7'' began preparations to dive.<ref name=combinedfleetI7/> At 19:30, Monaghan opened radar-directed gunfire {{convert|1|nmi}} south of the anchorage at a range of {{convert|2,000|yd|m|sigfig=2}}.<ref name=combinedfleetI7/> Taken by surprise,<ref name=Boydyoshidap119/> ''I-7'' prepared to crash-dive when her crew heard ''Monaghan''′s first shot, but two {{convert|5|in|mm|adj=on|sigfig=3}} shells immediately hit the starboard side of ''I-7''′s [[conning tower]], holing it and killing the submarine division commander, ''I-7''′s commanding officer, [[navigation officer]], and [[helmsman]], and two of ''I-7''′s [[non-commissioned officer]]s. ''I-7''′s [[communications officer]] was wounded.<ref name=combinedfleetI7/><ref name=Boydyoshidap119/>

''I-7''′s [[torpedo officer]] took command.<ref name=combinedfleetI7/> He ordered ''I-7'' to remain on the surface, man her guns, and return fire.<ref name=combinedfleetI7/> ''I-7'' fired thirty {{convert|140|mm|in|adj=on|sp=us|1}} rounds from her deck guns and 250 rounds from her machine guns.<ref name=combinedfleetI7/> Her crew had left her aft [[ballast tank]]s open by mistake, causing her to flood, take on a heavy list, and become stern-heavy.<ref name=combinedfleetI7/><ref name=Boydyoshidap119/> At around 19:45 she ran aground at Bukhti Point.<ref name=combinedfleetI7/> Her torpedo officer ordered her crew to abandon ship, and her [[paymaster]] destroyed her secret documents and smashed her coding machine, whose pieces he threw overboard.<ref name=combinedfleetI7/> Meanwhile, a Japanese [[Daihatsu-class landing craft|''Daihatsu''-class]] [[landing craft]] sent to unload cargo from ''I-7'' arrived in the area and tried to contact ''I-7'' in the thick fog by [[signal lamp]] but came under machine-gun fire from ''Monaghan'' and withdrew.<ref name=combinedfleetI7/>

Using a portable transmitter, ''I-7'' contacted Japanese forces ashore on Kiska at 02:00 on 21 June 1943.<ref name=combinedfleetI7/> Two ''Daihatsus'' arrived from Gertrude Cove with welding equipment, which ''I-7''′s crew used to patch the hole in her conning tower.<ref name=combinedfleetI7/> The ''Daihatsus'' also took aboard some of ''I-7''′s cargo for delivery ashore.<ref name=combinedfleetI7/> As acting commanding officer, the torpedo officer convened a meeting of surviving officers, who decided to make a high-speed run on the surface to Yokosuka, with a possible stop at Paramushiro.<ref name=combinedfleetI7/> With her repairs complete at 18:45, ''I-7'' entered Gertrude Cove by 19:00, unloaded the rest of her cargo and the bodies of deceased personnel and took aboard new code books.<ref name=combinedfleetI7/> She got underway at midnight on 21/22 June 1943.<ref name=combinedfleetI7/>

''Monaghan'' was patrolling in heavy fog south of Kiska when she again detected ''I-7'' on radar at a range of {{convert|14,000|yd|m|sigfig=3}} at 00:35 on 22 June 1943.<ref name=combinedfleetI7/> She closed the range, and at 01:30<!--Source says "0230," which apparently is a typo. Given the other times the source cites, 0230 makes no sense; it is either a typo or confusion between the ties used aboard ''I-7'' and ''Monaghan''. 0130 is probably the time ''Monaghan'' opened fire.--> opened radar-directed gunfire<ref name=combinedfleetI7/> when ''I-7'' was about {{convert|10|nmi}} south of Vega Bay.<ref name=Boydyoshidap119/> Again taking ''I-7'' by surprise, ''Monaghan'' scored several hits, including on the port side of ''I-7''′s conning tower, on her deck gun bulwark, and in her aft ballast tanks,<ref name=combinedfleetI7/> killing her engineering officer and severely wounding her acting commanding officer.<ref name=combinedfleetI7/> Her lookouts mistakenly reported her to be under fire from three different directions by three different ships.<ref name=combinedfleetI7/> ''I-7''′s gunnery officer, a [[lieutenant junior grade]], took command and ordered her crew to return fire with her deck guns and machine guns, and ''I-7''′s lookouts reported seeing a fire on one of the three ships they thought they had sighted.<ref name=combinedfleetI7/> ''Monaghan'' ceased fire after 10 minutes.<ref name=combinedfleetI7/>

''Monaghan'' resumed firing at 02:10, this time illuminating ''I-7'' with [[star shell]]s.<ref name=combinedfleetI7/> At around 02:18, she scored a hit which disabled ''I-7''′s steering engine, and ''I-7'' began a wide turn to port back towards Kiska.<ref name=combinedfleetI7/> Another hit detonated the ready-use ammunition for ''I-7''′s deck guns, which started a small fire.<ref name=combinedfleetI7/> The ventilation intakes for ''I-7''′s [[diesel engine]]s sucked in flames from the fire, threatening to set the [[Galley (kitchen)|galley]] and forward [[Head (watercraft)|head]] ablaze.<ref name=combinedfleetI7/> Two other hits breached the aft deck casing on ''I-7''′s port side, causing flooding which resulted in the submarine taking on a 30-degree list.<ref name=combinedfleetI7/><ref name=Boydyoshidap119/> ''I-7''′s crew suffered heavy casualties,<ref name=Boydyoshidap119/> and at 02:30, ''I-7''′s acting commanding officer ordered her to return to Kiska.<ref name=combinedfleetI7/><ref name=Boydyoshidap119/> ''Monaghan'' soon broke off her pursuit of ''I-7'' to avoid the danger of running aground off Kiska.<ref name=combinedfleetI7/>

''I-7''′s crew had fired seventy {{convert|140|mm|in|adj=on|sp=us|1}} shells and about 2,000 rounds from her machine guns during her battle with ''Monaghan''.<ref name=combinedfleetI7/> In danger of sinking,<ref name=Boydyoshidap119/> she reported her damage and estimated time of arrival to the Japanese forces on Kiska at 03:10.<ref name=combinedfleetI7/> At 03:15, she ran aground on the Twin Rocks off Vega Bay at {{coord|51|49|N|177|20|E|name=''I-7''}}.<ref name=combinedfleetI7/><ref name=Boydyoshidap119/> She sank quickly by the stern, trapping a number of men inside, and came to rest with the forward {{convert|50|ft|m|0}} of her [[Hull (ship)|hull]] out of the water.<ref name=combinedfleetI7/> She had lost 87 officers and men killed in combat with ''Monaghan'' or when she sank after running aground.<ref name=combinedfleetI7/><ref name=Boydyoshidap119/> A ''Daihatsu'' arrived at 06:30 and took off her 43 survivors.<ref name=combinedfleetI7/>

On 23 June 1943, a ''Daihatsu'' arrived on the scene, and [[Underwater diving|divers]] from it attempted to retrieve the codebooks aboard ''I-7'' when she sank.<ref name=combinedfleetI7/> Her surviving crew members had last seen a bag containing the code books and other secret documents suspended on a ladder at her No. 3 after access hatch, but the divers were unable to locate the books.<ref name=combinedfleetI7/> The ''Daihatsu'' then used [[demolition charge]]s to scuttle ''I-7''′s bow section.<ref name=combinedfleetI7/>

''I-7'' was stricken from the Navy list on 20 August 1943.<ref name=combinedfleetI7/>

==Aftermath==
The Japanese completed the evacuation of Kiska on 28 July 1943, and on 15 August 1943 the Allies invaded the undefended island in [[Operation Cottage]].<ref name=combinedfleetI7/> On 26 August 1943, the U.S. Navy [[fleet tug]] {{USS|Ute|ATF-76}} arrived to investigate ''I-7''′s wreck.<ref name=combinedfleetI7/> Her divers found ''I-7''′s wreck lying on its port side in {{convert|60|ft|m|0}} of water.<ref name=combinedfleetI7/> Although the conning tower was damaged, ''I-7''′s number was visible on a [[tarpaulin]] on the conning tower's side.<ref name=combinedfleetI7/>

On 7 September 1943, the U.S. Navy [[submarine rescue ship]] {{USS|Florikan|ASR-9}} arrived and began diving operations on the wreck that lasted for a month.<ref name=combinedfleetI7/> By the time the operations concluded in October 1943, seven divers had entered ''I-7''′s wreck and recovered valuable intelligence documents from it.<ref name=combinedfleetI7/>

==References==
===Footnotes===
{{Reflist}}

===Bibliography===
*Boyd, Carl, and Akihiko Yoshida. ''The Japanese Submarine Force and World War II''. Annapolis, Maryland: Naval Institute Press, 1995. {{ISBN|1-55750-015-0}}.

{{J type submarine}}
{{October 1941 shipwrecks}}
{{June 1943 shipwrecks}}

{{DEFAULTSORT:I-007}}
[[Category:Junsen type submarines]]
[[Category:Ships built by Kure Naval Arsenal]]
[[Category:1935 ships]]
[[Category:World War II submarines of Japan]]
[[Category:Attack on Pearl Harbor]]
[[Category:Friendly fire incidents of World War II]]
[[Category:Ships of the Aleutian Islands campaign]]
[[Category:Japanese submarines lost during World War II]]
[[Category:Maritime incidents in October 1941]]
[[Category:Maritime incidents in June 1943]]
[[Category:1943 in Alaska]]
[[Category:World War II shipwrecks in the Pacific Ocean]]
[[Category:Shipwrecks of the Alaska coast]]