AOSHIMA 1/700-scale WATER LINE SERIES WW2 JAPANESE NAVY SUBMARINES I-1 & I-6

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Additional Information from Internet Encyclopedia

I-1 was a J1 type submarine of the Imperial Japanese Navy. She was a large cruiser submarine displacing 2,135 tons and was the lead unit of the four submarines of her class. Commissioned in 1926, she served in the Second Sino-Japanese War and World War II. During the latter conflict she operated in support of the attack on Pearl Harbor, conducted anti-shipping patrols in the Indian Ocean, and took part in the Aleutian Islands campaign and the Guadalcanal campaign. In January 1943, during the Japanese evacuation of Guadalcanal, Operation Ke, the Royal New Zealand Navy minesweeper corvettes HMNZS Kiwi and HMNZS Moa intercepted her, and she was wrecked at Kamimbo Bay on the coast of Guadalcanal after the ensuing surface battle.

Construction and commissioning

Built by Kawasaki at Kobe, Japan, I-2 was laid down on 12 March 1923 with the name Submarine Cruiser No. 74.[5] She was launched on 15 October 1924.[5] Renamed I-1 on 1 November 1924, she was completed in late February 1926 and underwent sea trials—in which several German ship constructors participated—in the Seto Inland Sea off Awaji Island.[5] The Imperial Japanese Navy accepted her for service and commissioned her on 10 March 1926

Service history

Early service

On the day of her commissioning, I-1 was attached to the Yokosuka Naval District.[5] On 1 August 1926, she and her sister ship I-2 were assigned to Submarine Division 7 in Submarine Squadron 2 in the 2nd Fleet, a component of the Combined Fleet.[5] On 1 July 1927, the division was reassigned to the Yokosuka Defense Division in the Yokosuka Naval District, and on 15 September 1927, when Submarine Division 7 began another tour with Submarine Squadron 2 in the 2nd Fleet,[6] I-1 was removed from the division and reassigned directly to the Yokosuka Naval District. She returned to the division on 10 September 1928 during its assignment to Submarine Squadron 2. At 10:35 on 28 November 1928, as Submarine Division 7 returned to Yokosuka, Japan, in heavy seas and limited visibility, I-1 ran aground off Yokosuka.[5] She suffered minor damage.[5] No flooding occurred, but she was drydocked at Yokosuka to have her hull inspected.[5] On 5 November 1929, I-1 was decommissioned and placed in reserve,[5] and on 30 November 1929 Submarine Division 7 again was assigned to the Yokosuka Defense Division in the Yokosuka Naval District.

While in reserve, I-1 underwent modernization, in which her German-made diesel engines and entire battery installation were replaced.[5] On 1 August 1930, Submarine Division 7 began an assignment to Submarine Squadron 1 in the 1st Fleet, a component of the Combined Fleet, and, with her modernization work completed, I-1 was recommissioned on 15 November 1930[5] and rejoined the division.

On 1 October 1931, Submarine Division 7 was reassigned to the Yokosuka Defense Division in the Yokosuka Naval District, but it began another tour of duty in Submarine Squadron 1 in the 1st Fleet on 1 December 1931. It completed this assignment on 1 October 1932 and again was assigned to the Yokosuka Defense Division in the Yokosuka Naval District, then returned to Submarine Squadron 1 in the 1st Fleet for a third time on either 15 November 1933 or 15 November 1934,[5] according to different sources.

While I-1 was out of commission, her American-made sonar was replaced by a sonar system manufactured in Japan and her conning tower was streamlined.[5] Submarine Division 7 returned to duty with Submarine Squadron 1 in the 1st Fleet on 20 January 1936 and, after her reconstruction was complete, I-1 was recommissioned on 15 February 1936[5] and rejoined the division. On 27 March 1937, I-1 departed Sasebo in company with I-2, I-3, I-4, I-5, and I-6 for training in the vicinity of Qingdao, China. The six submarines concluded the training cruise with their arrival at Ariake Bay on 6 April 1937.

Second Sino-Japanese War

On 7 July 1937 the first day of the Marco Polo Bridge Incident took place, beginning the Second Sino-Japanese War.[12] In September 1937, Submarine Squadron 1 was reassigned to the 3rd Fleet,[13] which in turn was subordinated to the China Area Fleet for service in Chinese waters.[13] The squadron, consisting of I-1, I-2, I-3, I-4, I-5, and I-6,[13] deployed to a base at Hong Kong with the submarine tenders Chōgei and Taigei in September 1937.[13] From Hong Kong, the submarines began operations in support of a Japanese blockade of China and patrols of China′s central and southern coast.[13] From 20 or 21[5] (according to different sources) to 23 August 1937, all six submarines of Submarine Squadron 1 operated in the East China Sea as distant cover for an operation in which the battleships Nagato, Mutsu, Haruna, and Kirishima and the light cruiser Isuzu ferried troops from Tadotsu, Japan, to Shanghai, China.

Submarine Squadron 1 was based at Hong Kong until the autumn of 1938.[13] In an effort to reduce international tensions over the conflict in China, Japan withdrew its submarines from Chinese waters in December 1938.

1938–1941

On 10 November 1941, the commander of the 6th Fleet, Vice Admiral Mitsumi Shimizu, gathered the commanding officers of the fleet′s submarines together for a meeting aboard his flagship, the light cruiser Katori, anchored in Saeki Bay.[5] 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.[5] As the Imperial Japanese Navy began to deploy for the upcoming conflict in the Pacific, the rest of Submarine Squadron 1 got underway from Yokosuka on 16 November 1941, bound for the Hawaiian Islands.[12] At the time, I-1 was undergoing repairs—during which a very low frequency receiver was installed aboard her—at Yokosuka, so her departure was delayed, but on 23 November 1941 she too left Yokosuka. After an overnight stop in Tateyama Bight, she got underway for Hawaii, proceeding at flank speed to catch up with her squadron mates and remaining on the surface until within 600 nautical miles (1,100 km; 690 mi) of Oahu.

First war patrol

At 07:30 on 7 December 1941, I-1 sighted an Aichi E13A1 (Allied reporting name "Jake") floatplane returning to the heavy cruiser Tone after a reconnaissance flight over Lahaina Roads off Maui.[5] In the following days, she was attacked repeatedly by aircraft; although she suffered no damage, she began to keep her negative buoyancy tank flooded when surfaced so that she could dive more quickly.[5] While on the surface at 05:30 on 10 December 1941 she sighted a United States Navy aircraft carrier—probably USS Enterprise (CV-6)—24 nautical miles (44 km; 28 mi) north-northeast of Kahala Point on Kauai but was forced to submerge and was unable to transmit a sighting report for almost 12 hours.[5] She often is credited with a bombardment of Kahului, Maui, on 15 December 1941, although it actually was the submarine I-75 that shelled Kahului that day.

I-1 attacked a transport south of the Kauai Channel on 7 January 1942, but scored no hits.[5] On 9 January 1942, she was ordered to divert from her patrol and search for the United States Navy aircraft carrier USS Lexington (CV-2), which the submarine I-18 had sighted northeast of Johnston Island.[5] but she did not find Lexington. She arrived at Kwajalein in company with I-2 and I-3 on 22 January 1942.[5] The three submarines departed Kwajalein on 24 January 1942 bound for Yokosuka, which I-1 reached on 1 February 1942.

Second war patrol

While I-1 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 Invasion Force in the Southeast Area Force on 8 February 1942.[5] I-1 departed Yokosuka on 13 February 1942 bound for Palau, which she reached on 16 February.[5] After refueling from the oiler Fujisan Maru, she got back underway for the Netherlands East Indies on 17 February 1942 in company with I-2 and I-3.[5] She stopped at Staring Bay on the Southeast Peninsula of Celebes just southeast of Kendari, then put back to sea at 17:00 on 23 February 1942 to begin her second war patrol, bound for the Timor Sea[5] and Indian Ocean. Shortly after she left Staring Bay, her starboard diesel engine′s crankshaft broke down, but she pushed on, conducting most of her patrol on only one shaft.

On 9 March 1942, I-1 captured a canoe carrying five Australian Army personnel trying to reach Australia from Dutch Timor.[5] On 11 March 1942, she reached Staring Bay, where she moored alongside the submarine tender Santos Maru.[5] She transferred her prisoners to a hospital ship.[5] On 15 March 1942 she got underway for Yokosuka, which she reached on 27 March 1942.

March–June

After arriving at Yokosuka, I-1 was drydocked for repairs to her starboard diesel engine[5] and its crankshaft. She also underwent an overhaul in which shipyard workers replaced the 7.7-mm machine gun on her bridge with a 13.2-mm Type 93 machine gun and her Zeiss 3-meter (10 ft) rangefinder with a Japanese Type 97 rangefinder, removed some of the armor protecting her torpedo storage compartment, and installed an automatic trim system.[5] On 10 April 1942, she was reassigned along with I-2 and I-3 to the Advance Force.[5] On 18 April 1942, 16 United States Army Air Forces B-25 Mitchell bombers launched by the aircraft carrier USS Hornet (CV-8) struck targets on Honshu in the Doolittle Raid.[5] One B-25 targeted Yokosuka, and the members of I-1's crew on deck saw it damage the drydocked aircraft carrier Ryūhō, which was undergoing conversion from the submarine tender Taigei.

On 7 June 1942, I-1 took part in experiments in Tokyo Bay with a kite balloon intended for use by merchant ships.[5] She made several mock attack runs against a ship carrying a prototype of the balloon.

Fourth war patrol

While I-1 was at Yokosuka, the Aleutian Islands campaign began on 3–4 June 1942 with a Japanese air raid on Dutch Harbor, Alaska, followed quickly by the unopposed Japanese occupation in the Aleutian Islands of Attu on 5 June and Kiska on 7 June 1942. 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-1 set out for Aleutian waters in company with I-2, I-3, I-4, and I-7 to begin her fourth war patrol.[5] On 20 June 1942, I-1, I-2, and I-3 joined the "K" patrol line in the North Pacific Ocean between 48°N 178°W and 50°N 178°W.[5] In mid-July 1942, an unidentified American warship—possibly the United States Coast Guard cutter USCGC Onondaga (WPG-79)—attacked I-1 in the North Pacific Ocean south of Adak Island and pursued her for 19 hours before I-1 finally dived to 260 feet (79 m) and escaped.[5] On 20 July 1942, I-1 was reassigned to the Advance Force and received orders that day to return to Yokosuka, which she reached on 1 August 1942.

Guadalcanal campaign, 1942

During I-1'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.[5] On 20 August 1942, Submarine Squadron 2 was disbanded.[5] In late August 1942, I-2 underwent work at Yokosuka Navy Yard in which her after 140-millimeter (5.5 in) deck gun was removed and a mounting for a waterproofed 46-foot (14 m) Daihatsu-class landing craft was installed abaft her conning tower, which improved her ability to transport supplies to Japanese forces ashore in the Solomon Islands.[5] With the work completed in early September 1942, she began exercises with the Maizuru 4th Special Naval Landing Force (SNLF), which had been designated as "Special Landing Unit" for a raid the Japanese planned on Espiritu Santo in the New Hebrides.[5] I-1 was to land the SNLF personnel for the raid.

I-1 got underway on 1 October 1942 to carry supplies to a detachment of the Sasebo 5th SNLF on Goodenough Island, carrying a Daihatsu, the Daihatsu's three-man crew, and a cargo of food and ammunition.[5] At 22:40 on 3 October 1942 she surfaced off Kilia Mission on the southwestern tip of Goodenough Island and the Daihatsu took her cargo to shore.[5] She embarked 71 wounded SLNF personnel and the cremated remains of 13 others, recovered the Daihatsu, and returned to Rabaul, which she reached at 13:30 on 6 October 1942.[5] She set out again with another koad of food and ammunition on 11 October 1942.[5] She surfaced off Kilia Mission at 18:30 on 13 October and launched her Daihatsu. Allied intelligence had warned of her arrival, and a Royal Australian Air Force Lockheed Hudson Mark IIIA patrol bomber of No. 32 Squadron attacked the landing area, dropping flares and bombs, and I-1 submerged and departed, leaving her Daihatsu behind.[5] She reached Rabaul on 18 October 1942.

On 17 October 1942, I-1 was reassigned to the Advance Force, and on 22 October 1942 she left Rabaul to join a submarine patrol group operating south of San Cristobal in advance of the upcoming Battle of the Santa Cruz Islands,[5] fought from 25 to 27 October. On 28 October 1942, she received orders to search for downed Japanese air crews in the vicinity of the Stewart Islands.[5] She began to search the waters around the islands on 29 October, but soon had to abort her search when her starboard crankshaft failed again.[5] A U.S. Navy PBY-5 Catalina of Patrol Squadron 11 (VP-11) reported attacking a submarine on 29 October 1942 at 13°15′S 162°45′E, and its target most likely was I-1.[5] I-1 proceeded to Truk.[5] She departed Truk at 17:00 on 13 November 1942 bound for Yokosuka, which she reached at 16:30 on 20 November 1942.

November 1942–January 1943

On 3 January 1943, I-1 put to sea from Yokosuka bound for Truk, which she reached at 18:00 on 10 January 1943.[5] After arriving, she unloaded all but two of her torpedoes[5] and received her Daihatsu. At 06:30 on 12 January 1943 she put to sea to conduct Daihatsu launch tests, but was back at her anchorage at 08:30 to repair the air induction valve for her diesel engines.[5] She conducted more launch tests on 14 January, and on 15 January she got underway at 13:00 for nighttime launch tests, returning to port by 20:00.

Guadalcanal campaign, 1943

At 19:00 on 16 January 1943, I-1 left Truk for Rabaul, where she arrived at 07:30 on 20 January 1943.[5] She took aboard a cargo of rubber containers loaded with two days of food rations—rice, bean paste, curry, ham, and sausages—for 3,000 men.[5] At 16:00 on 24 January 1943, she departed Rabaul bound for Guadalcanal, where she was to deliver her cargo at Kamimbo Bay on the island's northwest coast.

On 26 January 1943, the commander of Allied naval forces in the Solomon Islands informed all Allied ships in the Guadalcanal–Tulagi area of the possibility of Japanese supply submarines arriving at Kamimbo Bay on the evenings of 26, 27, and 29 January 1943.[5] The Royal New Zealand Navy minesweeper corvettes HMNZS Kiwi and HMNZS Moa received orders to conduct an antisubmarine patrol in the Kamimbo Bay area.[5] For its part, the Japanese 6th Fleet warned Submarine Division 7 that Allied motor torpedo boats were operating in the vicinity of Kamimbo Bay and advised them to unload supplies only after dark.

Loss

I-1 surfaced off Kamimbo Bay in a heavy rain squall at 20:30 on 29 January 1943 and headed towards shore, trimmed with her decks awash.[5][14] At 20:35,[14] Kiwi, which was patrolling with Moa off Kamimbo Bay, detected I-1, first with her listening gear and then with asdic, at a range of 3,000 yards (2,700 m).[5][14][15] Moa attempted to confirm the contact, but could not.[5][14] Kiwi closed the range.[5][14] When one of I-1's lookouts sighted Kiwi and Moa—misidentifying them as torpedo boats—I-1 turned to port and submerged, diving to 100 feet (30 m), and rigging for silent running.[5][14] Kiwi saw I-1 submerging and moved in to attack, dropping 12 depth charges in two patterns of six.[5][14] The depth charges detonated close to I-1, knocking several of her men off their feet, and I-1 sprang a leak in her aft provision room.

At 21:20, Kiwi turned toward I-1 at full speed at a distance of 400 yards (370 m). I-1's gunners were unable to hit Kiwi, which was partially shielded by I-1's conning tower, and Kiwi rammed her on her port side abaft her conning tower.[5][14] As Kiwi backed off, she came into the unobstructed field of fire of I-1's deck gun, and I-1's gunners claimed hits that set Kiwi on fire, although in fact no fire broke out aboard Kiwi.[5][14] Believing they were in combat with torpedo boats, I-1's lookouts also reported seeing three torpedoes pass close aboard,[5][14] although the two New Zealand corvettes had no torpedo armament.

At 23:15, I-1 ran hard aground on Fish Reef off the coast of Guadalcanal, 330 yards (300 m) north of Kamimbo Bay. The entire after half of her hull flooded, and she developed a heavy list to starboard. Sixty-six men abandoned ship, and not long afterward I-1 sank at 09°13′S 159°40′E. She came to rest with 15 feet (4.6 m) of her bow projecting from the water at a 45-degree angle.

I-1 suffered 27 killed or missing in the battle with Kiwi and Moa.[5][14] Sixty-eight men survived, including two men who went overboard during the battle and swam to Guadalcanal separately from the other survivors.[5][14] The only fatality on the New Zealand side was Kiwi's searchlight operator, who remained at his post despite suffering a mortal gunshot wound during Kiwi's second ramming attempt and died two days later.[5][15] Between them, the two corvettes expended fifty-eight 4-inch (102 mm) rounds, claiming 17 hits and seven probable hits, as well as an estimated 1,259 rounds of Oerlikon ammunition and 3,500 rounds from small arms.

Salvage and demolition attempts

Moa patrolled off I-1's wreck until dawn on 30 January 1943, when she closed to inspect it.[5][15] She found two survivors at the wreck, capturing one and killing the other with machine-gun fire.[5][15] She also retrieved nautical charts and what she believed was a code book, although it more likely was I-1's logbook.[5] Japanese artillery ashore opened fire on Moa, forcing her to leave the area.

Sixty-three of I-1's survivors were evacuated from Guadalcanal on 1 February 1943.[5] When they reached Rabaul and were debriefed, the Japanese concluded that code materials aboard her wreck were in danger of compromise.[5] Meanwhile, I-1's torpedo officer, two of her junior officers, and 11 men from Japanese destroyers reached the wreck in a Daihatsu after 19:00 on 2 February 1943.[5] They attached two depth charges and four smaller demolition charges to the wreck and set them off in an attempt to destroy it by detonating torpedoes still aboard I-1.[5] Although the torpedoes did not explode and the wreck was not destroyed, the depth charges caused enough damage to prevent salvage of I-1.[5] Evacuated from Guadalcanal on 7 February 1943—the day the Guadalcanal campaign ended with the completion of Operation Ke, the Japanese evacuation of all forces from the island—the three officers subsequently reported their failure to destroy the wreck after they arrived at Rabaul.[5]

On 10 February 1943, the Japanese made another attempt to destroy I-1's wreck, when nine Buin-based Aichi D3A1 (Allied reporting name "Val") dive bombers from Bougainville escorted by 28 Mitsubishi A6M Zero (Allied reporting name "Zeke") fighters attacked it.[5] Most of the dive bombers failed to find the wreck, but one scored a hit on it near the conning tower with a 250-kilogram (551 lb) bomb.[5] On 11 February 1943, I-2 departed Shortland Island with I-1's torpedo officer aboard, tasked with finding and destroying I-1's wreck.

The crew of the U.S. Navy PT boat PT-65 and embarked intelligence personnel inspect the wreck of I-1 on 11 February 1943.

As the Japanese feared, the Allies began to investigate I-1's wreck in the hope of recovering intelligence from it. On 11 February 1943, the day I-2 got underway from Shortland Island, the U.S. Navy PT boat PT-65 arrived at the wreck carrying United States Army intelligence officers[5] who assessed the potential of the wreck to yield useful information. The submarine rescue vessel USS Ortolan (ASR-5) inspected the wreck of I-1 on 13 February 1943, and her divers recovered five code books and other important communications documents.[5] That evening, I-2 penetrated Kamimbo Bay to a distance of only 1,100 yards (1,010 m) from shore but failed to find I-1's wreck.[5][12] On 15 February 1943—the day the Imperial Japanese Navy decided to consider all code materials aboard I-1 compromised and revised and upgraded its codes[5]—she tried again, reaching a point 1.4 nautical miles (2.6 km; 1.6 mi) from the coast before motor torpedo boats attacked her with depth charges.[5][12] After an aircraft also attacked her at 11:20, I-2 gave up and returned to Shortland Island.[12] Ultimately, the U.S. Navy reportedly salvaged code books, charts, manuals, the ship's log, and other secret documents, as well as equipment, from the wreck of I-1.

The Japanese struck I-1 from the Navy list on 1 April 1943.

Postscript

I-1's gun on display at the Torpedo Bay Navy Museum in Auckland, New Zealand, in June 2012.

In 1968, I-1's main deck gun was salvaged and brought to Auckland, New Zealand, aboard the frigate HMNZS Otago[16] for display at the Torpedo Bay Navy Museum.

In 1972, an Australian treasure hunter in search of valuable metals blew up the bow section of I-1  With live torpedoes still inside, the explosion destroyed the forward third of the submarine, with the bow section split open. The after two-thirds of the wreck remained intact. I-1's wreck lies on an incline with the remains of her bow in 45 feet (14 m) of water and her stern at a depth of 90 feet (27 m).

I-1's pennant is on display in the United States at the National Museum of the Pacific War in Fredericksburg, Texas.

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I-6 was an Imperial Japanese Navy J2 type submarine commissioned in 1935. She was a large cruiser submarine that served in the Second Sino-Japanese War and World War II. During the latter conflict she operated in support of the attack on Pearl Harbor, torpedoed the aircraft carrier USS Saratoga (CV-3), conducted anti-shipping patrols in the Indian Ocean and South Pacific Ocean, and took part in the Aleutian Islands campaign and New Guinea campaign before she was sunk in June 1944.

Design

I-6 was the only Junsen II- (or "J2"-) type submarine. After the four Junsen I-type submarines (I-1, I-2, I-3, and I-4), the Japanese had built I-5 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 represented the next step in the evolution of this aviation capability, as she had both a hangar and a catapult for a floatplane. The next and last Junsen-type submarines, I-7 and I-8, the only Junsen III-type submarines, also each had a hangar and catapult for a floatplane.

Construction and commissioning

Built by Kawasaki at Kobe, Japan, I-6 was laid down on 14 October 1932. She was launched on 31 March 1934 and completed and commissioned on 15 May 1935.

Service history

1935–1937

Upon commissioning, I-6 was attached to the Yokosuka Naval District. On 1 June 1935, she was assigned to Submarine Division 8 in Submarine Squadron 1 in the 1st Fleet, a component of the Combined Fleet. She was taking part in maneuvers off Ise Bay at 14:27 on 1 August 1935 when she collided with the destroyer Akatsuki. She suffered damage to her periscopes and proceeded to Yokosuka, Japan, for repairs. She was reassigned directly to the Yokosuka Naval District on 15 November 1935. In July 1936, she embarked a Watanabe E9W1 (Allied reporting name "Slim") reconnaissance seaplane for testing purposes.

Second Sino-Japanese War

On 7 July 1937 the first day of the Marco Polo Bridge Incident took place, beginning the Second Sino-Japanese War. In September 1937 Submarine Squadron 1 was reassigned to the 3rd Fleet,[8] which in turn was subordinated to the China Area Fleet for service in Chinese waters.[8] The squadron, consisting of I-1, I-2, I-3, I-4, I-5 and I-6,[8] deployed to a base at Hong Kong with the submarine tenders Chōgei and Taigei in September 1937.[8] From Hong Kong, the submarines began operations in support of a Japanese blockade of China and patrols of China's central and southern coast.[8] From 20 or 21 (sources disagree) to 23 August 1937, all six submarines of Submarine Squadron 1 operated in the East China Sea as distant cover for an operation in which the battleships Nagato, Mutsu, Haruna, and Kirishima and the light cruiser Isuzu ferried troops from Tadotsu, Japan, to Shanghai, China.

Submarine Squadron 1 was based at Hong Kong until the autumn of 1938.[8] In an effort to reduce international tensions over the conflict in China, Japan withdrew its submarines from Chinese waters in December 1938.

1938–1941

Remaining a unit of Submarine Division 8, I-6 was placed in Second Reserve in the Yokosuka Naval District on 15 December 1938, then on 1 April 1939 began an assignment at the Torpedo School in the Yokosuka Naval District at Yokosuka. In mid-1940, her hangar and catapult were removed, and thereafter she did not operate aircraft. Submarine Squadron 2, including I-6, was resubordinated to the 6th Fleet on 15 November 1940.

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. The submarines had orders to conduct reconnaissance in the area and attack any ships which sortied from Pearl Harbor during or after the attack, which occurred that morning. I-6′s patrol area was between those of I-4 and I-5 and was located off the northern entrance of Kaiwi Channel between Molokai and Oahu. At 08:40 on 9 December 1941, I-6 sighted the United States Navy aircraft carrier USS Enterprise (CV-6) — which she misidentified as a Lexington-class aircraft carrier — and two heavy cruisers north of Molokai steaming northeast at 20 knots (37 km/h; 23 mph). She attempted to attack Enterprise, but was forced to go deep before she could. Several hours later she managed to transmit a sighting report, which resulted in the Japanese ordering nine submarines to attempt to intercept Enterprise, which they assumed was bound for the United States West Coast. Out of position to participate in the pursuit of Enterprise, I-6 was ordered to take up a new patrol area south of Oahu in waters between the Kauai Channel and an area southeast of Pearl Harbor. Later in December, one of her torpedomen was injured during a routine torpedo inspection; he died several days later of sepsis on 27 December 1941 and was buried at sea.

On 9 January 1942, the submarine I-18 reported sighting a Lexington-class aircraft carrier 270 nautical miles (500 km; 310 mi) northeast of Johnston Island, and the 6th Fleet ordered a number of submarines including I-1 to form a picket line northeast of Johnston Island to find the carrier. When I-1 developed engine trouble, I-6 received orders to replace her in the picket line. During the daylight hours of 10 January 1942, I-6′s lookouts sighted planes from the carrier on five separate occasions, and her navigator plotted their courses and used the information to estimate the carrier's position. While on the surface 270 nautical miles (500 km; 310 mi) northeast of Johnston Island at 18:41 on 11 January 1942, she sighted a U.S. Navy destroyer and submerged. Not long afterwards, the aircraft USS Saratoga (CV-3) hove into view at 19°N 165°W, steaming southeast at 15 knots (28 km/h; 17 mph) and accompanied by a heavy cruiser and another destroyer. I-6 fired three Type 89 torpedoes at Saratoga at a range of 4,700 yards (4,300 m), and at 19:15 one of them hit Saratoga amidships on her port side, killing six firemen and flooding three boiler rooms. Taking on 1,100 tons of water, Saratoga heeled to starboard and then to port and lost headway. I-6 went to a depth of 330 feet (100 m), and when the escorting destroyers began a counterattack at 19:58, they could not locate her. Her sound operator reported hearing two large explosions followed by a number of smaller ones which suggested that Saratoga had sunk and was breaking up on her way to the bottom, and after 22:00 I-6 transmitted a report claiming two hits on, and the probable sinking of, a Lexington-class aircraft carrier. In fact, Saratoga survived, but the damage I-6 inflicted kept her out of combat for the next six months.

On 12 January 1942, I-6 departed her patrol area bound for Kwajalein, which she reached on 22 January 1942 with only 800 liters (180 imp gal; 210 U.S. gal) of fuel left. She got back underway on 24 January 1942 bound for Yokosuka, which she reached on 2 February 1942. She was drydocked in early February 1942 and began a refit and overhaul.

Second war patrol

While I-6 was at Yokosuka, Submarine Squadron 2 — consisting of I-1, I-2, I-3, I-4, I-6, and the squadron flagship, I-7 — was assigned to the Dutch East Indies Invasion Force in the Southeast Area Force on 8 February 1942. On 13 February, the staff of Submarine Division 8 transferred from I-6 to I-4, and I-6 departed Yokosuka on 14 February 1942 bound for the Netherlands East Indies. She arrived at Staring Bay on the Southeast Peninsula of Celebes just southeast of Kendari on 22 February 1942. At 07:00 on 23 February 1942, she got back underway in company with I-4 and I-5 to begin her second war patrol, bound for a patrol area in the Indian Ocean west of Sumatra. While I-5 and I-6 were on the surface west of Timor en route their patrol areas on 25 February 1942, an Imperial Japanese Navy Mitsubishi C5M (Allied reporting name "Babs") reconnaissance aircraft escorted by nine Mitsubishi A6M Zero (Allied reporting name "Zeke") fighters sighted the vessels at 12:30 Japan Standard Time and misidentified them as Royal Netherlands Navy submarines. The Zeroes made repeated strafing attacks that forced I-6 to submerge, but she suffered no damage. Her patrol otherwise was uneventful, and she concluded it with her arrival at Penang in Japanese-occupied British Malaya on 8 March 1942.

Third war patrol

Orders arrived from the 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 Mobile Force. Accordingly, I-6 departed Penang on 26 March 1942 to begin her third war patrol, assigned a patrol area in the Indian Ocean west of Bombay, India, and north of the Maldive Islands. On 27 March, the German naval staff in Berlin asked that Japan begin anti-shipping operations against Allied convoys in the Indian Ocean.

At 16:35 on 31 March 1942, I-6 was in the Indian Ocean off Eight Degree Channel when she sighted an Allied steamer. She commenced an approach and was about to fire torpedoes when she identified the ship as a hospital ship — probably the British hospital ship HMHS Vita on a voyage from Addu Atoll to the Ceylon area — and called off the attack. On the afternoon of 2 April 1942, I-6 was in the Arabian Sea 300 nautical miles (560 km; 350 mi) southwest of Bombay when she sighted the British 5,897-ton steamer Clan Ross, which was on her way from Liverpool, England, to Cochin, India, carrying 3,655 tons of general cargo and 1,027 tons of explosives. She fired two torpedoes at a range of 1,640 yards (1,500 m), scoring one hit amidships on Clan Ross′s port side. Clan Ross sank by the stern at 14:14 at 15°58′N 068°24′E with the loss of 11 crew members killed and three injured. I-6 surfaced and approached the survivors. I-6′s crew interrogated the survivors, provided them with fresh water and biscuits, and gave them the bearing to Bombay, then lined up on I-6′s afterdeck, saluted the survivors, and wished them "bon voyage" in broken French.

While on the surface at around 16:00 on 7 April 1942, I-6 encountered the British 5,424-ton merchant ship Bahadur — bound from Bombay to Basra, Iraq, with a cargo of 5,100 tons of government stores and ammunition — in the Arabian Sea 170 nautical miles (310 km; 200 mi) northwest of Bombay. I-6 submerged and fired torpedoes, but Bahadur′s crew spotted them and Bahadur made a hard turn to starboard, evaded the torpedoes, and attempted to open the range at top speed. I-6 fired two torpedoes from her stern torpedo tubes, but they also missed. She then surfaced and pursued Bahadur, opening fire with her 127-millimeter (5 in) deck gun at a range of 6,570 yards (6,010 m). The gun jammed after firing only one round, and I-6 submerged and gave up the chase. Bahadur suddenly stopped, however, and lowered her lifeboats. I-6 closed and fired two more torpedoes from a position on Bahadur′s port beam. Bahadur sank by the stern at 19:20 at 19°44′N 068°28′E.

I-6 surfaced in the Arabian Sea 300 nautical miles (560 km; 350 mi) southwest of Bombay after 08:15 on 10 April 1942 to attack two 150-ton dhows with her deck gun, claiming both of them sunk. Her patrol ended with her arrival at Seletar, Singapore, on 17 April 1942. She departed Singapore on 21 April 1942 in company with I-5 to head for Yokosuka, which she reached on 1 May 1942. She underwent repairs there until 6 June 1942.

Fourth war patrol

While I-6 was at Yokosuka, the Aleutian Islands campaign began on 3–4 June 1942 with a Japanese air raid on Dutch Harbor, Alaska, followed quickly by the unopposed Japanese occupation in the Aleutian Islands of Attu on 5 June and Kiska on 7 June 1942. 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 either 17 or 20 June 1942 I-6 set out for Aleutian waters to begin her fourth war patrol. She joined the "K" patrol line in the Unimak Pass area. On 7 July 1942, she received orders to move to the Kiska area. When the rest of Submarine Squadron 2 was ordered to return to Japan on 20 July 1942, she was ordered to remain behind and operate from Kiska.

On 29 July 1942, an Imperial Japanese Navy Kawanishi H6K (Allied reporting name "Mavis") flying boat reported an American seaplane tender at Natan Bay on the coast of Adak Island. I-6 went to investigate, but found nothing. She was anchored off Kiska along with the submarines Ro-61, Ro-64, and Ro-68 when the cruisers and destroyers of U.S. Navy Task Group 8.6 bombarded the island and harbor on 7 August 1942. All four submarines submerged to avoid damage, and some of them set off in pursuit of the task group after the shelling ceased, but none succeeded in finding the withdrawing American ships.

On 15 August 1942, I-6 received orders to return to Japan, and she got underway from Kiska the same day. While she was at sea, both Submarine Squadron 2 and Submarine Division 8 were disbanded, and she and I-5 were reassigned to Submarine Division 7. She arrived at Yokosuka on 23 August 1942 and began an overhaul.

August 1942–February 1943

While I-6 was at Kiska, the six-month 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. As the campaign wore on, the Japanese decided to use submarines to supply their forces fighting on Guadalcanal and began fitting the submarines involved in the supply runs with a mounting on their decks that allowed each of them to carry a waterproofed Daihatsu-class landing craft for the discharge of cargo along coastlines in the Solomon Islands. I-6 received a Daihatsu mounting during her overhaul, but was still in Japan when Operation Ke, the evacuation of Japanese forces on Guadalcanal, was completed on 7 February 1943, bringing the Guadalcanal campaign to an end.

With her overhaul complete, I-6 departed Yokosuka at 10:00 on 16 February 1943 carrying a Daihatsu. She arrived at Truk at 10:15 on 23 February 1943, and later that day the commander of Submarine Squadron 7 came aboard to inspect her. On 26 February 1943 she debarked her Daihatsu and took on fuel, supplies, and ammunition from Hie Maru. She departed her anchorage at 08:00 on 28 February 1943, made a test cruise off Uman Island, and returned at 15:00.

Fifth war patrol

On 2 March 1943, I-6 got underway from Truk for her fifth war patrol, tasked with laying nine German-made TMC magnetic mines off Brisbane, Australia, and patrolling in the South Pacific Ocean off the east coast of Australia. On 4–5 March 1943, she transited St. George's Channel off New Ireland southbound. On 8 March 1943, Fleet Radio Unit, Melbourne (FRUMEL), an American-Australian-British signals intelligence unit headquartered at Melbourne, Australia, decrypted a Japanese message — probably one transmitted on 2 March — that revealed I-6′s departure.

FRUMEL's reporting prompted instructions to coastal artillery forces to watch for a Japanese submarine and the Royal Australian Air Force (RAAF) stepped up its patrol efforts along the east coast of Australia, using Avro Anson and Bristol Beaufort aircraft.[9] I-6 was forced to remain submerged during daylight hours by the increased RAAF activity,[10] but she patrolled uneventfully between Fraser Island and Stradbroke Island from 14 to 16 March 1943. At 12:00 on 17 March 1943 she was southeast of Sandy Cape at 25°49′S 153°49′E. At 14:30 she sighted the two-ship Convoy BT-44 — which consisted of the armed Liberty ships Charles C. Jones and Joseph Holt escorted by the Royal Australian Navy minesweeper-corvette HMAS Gympie — just north of Point Cartwright.[10] She fired two Type 89 torpedoes at Charles C. Jones at long range at 15:07, and at 15:11 Charles C. Jones sighted their wakes passing 20 yards (18 m) astern of her.[10] Charles C. Jones and Joseph Holt, which both turned to avoid the torpedoes, opened fire to alert Gympie.[10] An Anson of the RAAF's No. 71 (Reserve) Squadron patrolling overhead also sighted the wakes and dropped a sea marker at I-6′s presumed location. Gympie and the Anson then searched for I-6 until 15:30, and the Anson dropped a depth charge at 15:32, but I-6 escaped unscathed. At 20:22, she transmitted a situation report which FRUMEL intercepted and partly decrypted, and as a result two U.S. Navy patrol vessels arrived in the area and searched for her until sunset on 18 March 1943, but without success.

Unfortunately for the Japanese, I-6′s commanding officer lacked adequate intelligence on Allied shipping patterns when I-6 laid her mines, which were planted in an area rarely visited by Allied ships.[10 They went unnoticed until 24 March 1943, when the Royal Australian Navy sloop-of-war HMAS Swan visited the area to conduct antiaircraft gunnery practice, firing at a target towed by an RAAF Lockheed Hudson.[10] As spent shells and shell fragments fell into the water, Swan observed two large explosions close aboard which reached 400 feet (122 m) in height and 130 feet (40 m) across their bases. At least two mines clearly had exploded, and the size of the explosions suggested that each of them separately may have represented the detonation of two mines, although Allied forces could not substantiate this possibility. Gympie arrived in the area and began a minesweeping effort that after a number of days detonated another mine, but repeated sweeping found no more by the time minesweeping operations ended in September 1943.[10] The mines were designed to rest on the seafloor and were not fixed in place, meaning that they could slide or roll if laid on sloping surfaces, and the Allies found the mines in a somewhat different location — 8 nautical miles (15 km; 9.2 mi) offshore in waters 30 to 40 meters (98 to 131 ft) deep[10] — than I-6 reported laying them.

New Guinea campaign

While I-6 was on patrol, a Japanese attempt to carry supplies and reinforcements to New Guinea for their forces fighting in the New Guinea campaign in a convoy of eight ships escorted by eight destroyers ended in disaster in the Bismarck Sea when Allied aircraft sank all eight ships and four of the destroyers in the Battle of the Bismarck Sea, fought from 2 to 4 March 1943. The Japanese decided to use submarines instead to carry supplies and troops to New Guinea. Accordingly, on 29 March 1943 I-6 was reassigned to the Southeast Area Fleet for duty running supplies to Lae on the coast of New Guinea. She got underway from Rabaul for her first supply run on 3 April 1943, carrying 30 passengers and 77 supply drums containing 3.3 tons of weapons and ammunition, 22 tons of clothing, and 15.4 tons of food. She arrived at Lae on the coast of New Guinea on 5 April 1943, where she disembarked her passengers and discharged her cargo onto Daihatsus. She brought aboard four Imperial Japanese Army soldiers who were taking the regimental colors of the 41st Infantry Regiment to Rabaul and 25 other passengers and departed for Rabaul. Shortly after her departure she sighted Allied motor torpedo boats, but she crash-dived and avoided them and arrived safely at Rabaul on 7 April 1943.

I-6 next called at Lae on 11 April 1943, unloading 26 passengers and 77 supply drums containing 4.4 tons of weapons and ammunition, 19 tons of clothing, and food and embarking 42 passengers for Rabaul. On her third supply run, she visited Lae on 17 April 1943, discharging 28 passengers and 77 supply drums containing four tons of weapons and ammunition and 17 tons of clothing. After embarking 39 passengers, she got back underway for Rabaul. She sighted Allied motor torpedo boats near the Tami Islands during the return trip, but submerged and avoided them. While at Rabaul, she was reassigned on 21 April 1943 to the Northern District Force in the 5th Fleet to support the supply and reinforcement of the Japanese garrisons on Attu and Kiska in the Aleutian Islands.

I-6′s seventh run was more eventful. She arrived at Lae on 13 May 1943, unloaded 10 passengers and supply drums containing 11.5 tons of weapons, five tons of ammunition, and nine tons of food. After embarking four passengers, she began her return trip to Rabaul. Shortly thereafter, the U.S. Navy PT boats PT-150 and PT-152 sighted I-6 making 12 knots (22 km/h; 14 mph) on the surface 5 nautical miles (9.3 km; 5.8 mi) off Lae at a range of 6,000 yards (5,500 m). Each PT boat fired two torpedoes at I-6 at long range, but I-6 stopped and the torpedoes missed ahead of her. PT-150 then closed to 4,000 yards (3,700 m) and fired another torpedo at the stationary I-6, but the submarine suddenly accelerated and the torpedo missed astern. The PT boats then ran parallel to I-6′s course and turned toward her to decrease the range, but she submerged. The PT boats then stopped, and I-6 fired a torpedo at them, which passed under PT-150′s bow without detonating, bringing the action to a close. I-6 proceeded with her voyage to Rabaul, but on 14 May 1943 she diverted from it so that she and I-5 could search for the crews of Mitsubishi G4M (Allied reporting name "Betty") bombers shot down during a raid on Oro Bay. She rescued two aviators from the water 60 nautical miles (110 km; 69 mi) off Buna, New Guinea.

On her eighth run, I-6 called at Lae on 21 May 1943 to deliver 5.1 tons of weapons, 5.4 tons of ammunition, 4.6 tons of food, and 31 passengers. She departed for Rabaul after embarking 40 passengers. On her ninth and final run, she visited Lae on 28 May 1943 and dropped off 18 tons of food, 4.3 tons of weapons and medicine, two tons of clothes, a Daihatsu, and 23 passengers. Not scheduled to return to Rabaul, she did not embark passengers. She instead got back underway bound directly for Truk. Reassigned along with I-5 to the 6th Fleet while at sea on 31 May 1943, she stopped at Truk from 1 to 2 June 1943, then proceeded to Yokosuka, which she reached on 8 June 1943. She underwent repairs there.

Sixth and seventh war patrols

In the Aleutian Islands, the Japanese garrison on Attu had been annihilated by invading U.S. forces in the Battle of Attu between 11 and 30 May 1943. On 21 May 1943, with the situation on Attu deteriorating, the Japanese Imperial General Headquarters decided to evacuate the isolated garrison on Kiska. The evacuation began by submarine on 26 May 1943. Submarine Division 7 was reassigned to the 5th Fleet on 1 July 1943, and on either 1 or 2 July I-6 set out from Yokosuka on her sixth war patrol, bound for Paramushiro in the Kuril Islands. After calling at Paramushiro, she deployed to support the ongoing evacuation of Kiska, patrolling with I-5 in the Bering Sea north-northeast of Kiska. Between 17 and 19 July 1943, the two submarines sighted three U.S. destroyers on three separate occasions, but were unable to attack them. The Japanese completed the evacuation on 28 July 1943, and I-6 concluded her patrol with her arrival at Paramushiro on 4 August 1943.

I-6 departed Paramushiro on 16 August 1943 for her seventh war patrol, assigned a patrol area off Kiska. The patrol was uneventful, and she returned to Paramushiro on 3 September 1943. She got back underway on 5 September 1943 and arrived on 10 September at Yokosuka, where she underwent repairs.

New Guinea and Bismarck Archipelago

n a new series of supply runs, shuttling between Rabaul and Iboki, New Guinea. Her first and second round trips — from 4 to 10 January 1944, calling at Iboki on 6 January, and from 17 to 21 January 1944, calling at Iboki on 19 January — involved the delivery of supplies. On her third run, in which she departed Rabaul on 28 January 1944, she carried only troops, which she disembarked at Iboki on 30 January 1944, damaging her screws on an uncharted reef in the process. She returned to Rabaul on 1 February 1944, and on that day Submarine Division 7 was attached directly to 6th Fleet headquarters. Her next supply trip saw her depart Rabaul on 3 February 1944 to deliver supplies to Sarmi, New Guinea. She received orders on 5 February 1944 to return to Yokosuka. She got underway from Rabaul on 13 February 1944, called at Lorengau on Manus Island in the Admiralty Islands on 17 February 1944 to deliver a cargo of 12 heavy machine guns and their ammunition, then departed the same day for Yokosuka, which she reached on 29 February 1944 to begin an overhaul.

Loss

On 15 June 1944, the Marianas campaign began with the U.S. invasion of Saipan. Anticipating the invasion, on 13 June 1944 the commander of the 6th Fleet, Vice Admiral Takeo Takagi, ordered all available Japanese submarines to deploy east of the Mariana Islands. With her overhaul recently completed, I-6 set out from Yokosuka bound for the waters off Saipan on 16 June 1944. At 22:33 that evening the Japanese 5,123-ton armed cargo ship Toyokawa Maru — a member of Convoy 3606, consisting of four merchant ships escorted by three coastal defense ships and a submarine chaser, which had left Ogasawara in the Bonin Islands on 14 June 1944 bound for Yokosuka — sighted I-6 surfacing near the convoy. Mistaking her for an enemy submarine, Toyokawa Maru sounded a submarine alert, turned sharply toward I-6, and rammed her on her starboard side just abaft her conning tower. I-6 listed heavily, capsized, and sank a few minutes later, and Toyokawa Maru followed up by dropping depth charges and machine gunning the water where I-6 sank. None of I-6′s crew of 104 survived.

On 1 July 1944, the Japanese ordered I-6 to rescue Takagi and his staff from their headquarters on Saipan, which was threatened by advancing American forces. When I-6 did not acknowledge receipt of the message, the Japanese declared her missing. Sixth Fleet headquarters made a final attempt to contact her on 3 July 1944.

Alternative accounts of the loss of I-6 claim that Toyokawa Maru sank her off Saipan on 30 June 1944, or that the destroyer escort USS William C. Miller (DE-259) and high-speed transport USS Gilmer (APD-11) sank her 70 nautical miles (130 km; 81 mi) west of Tinian at 15°18′N 144°2