(Type J2 submarine)

IJN Submarine I-6:
Tabular Record of Movement

2001-2012 Bob Hackett & Sander Kingsepp
Revision 8

14 October 1932:
Kobe. Laid down at Kawasaki's ship yard.

31 March 1934:

25 August 1934:
LtCdr (promoted Cdr 15 November; later Captain) Kijima Moriji (44)(former CO of I-5) is appointed the Chief Equipping Officer (CEO).

15 May 1935:
Completed and attached to Yokosuka Naval District. Cdr Kijima Moriji is the CO.

25 May 1935:
LtCdr (later Captain) Nagai Takeo (47)(former CO of I-23/I-123) is appointed the CO.

1 August 1935:
Off Ise Bay. At 1427, during joint maneuvers, submerged I-6 collides with destroyer AKATSUKI, damaging her periscopes. Departs the area for Yokosuka for repairs.

July 1936:
One Watanabe E9W1 Type 96 "Slim" floatplane is embarked for testing purposes.

1 December 1936:
Cdr (later Captain) Okada Yusaku (47)(former CO of I-63) is appointed the CO.

21-23 August 1937:
East China Sea. Submarines I-6, I-1, I-2, I-3, I-4 and I-5 provide distant cover for BatDiv 1's NAGATO, MUTSU, BatDiv 3's HARUNA and KIRISHIMA and light cruiser ISUZU ferrying troops from Tadotsu, Shikoku, to the Shanghai area.

15 November 1937:
LtCdr (promoted Cdr 1 December; later Captain) Oyama Toyojiro (47)(former CO of I-67) is appointed the CO.

1 November 1939:
Cdr (later Captain) Nagai Komei (48)(former CO of I-75) is appointed the CO.

Aircraft installation is removed. Probably at that time the conning tower is rebuilt, replacing the machine gun with a Type 96 25-mm AA gun.

30 October 1940:
Cdr (later Captain) Narahara Seigo (48)(former CO of I-58) is appointed the CO.

15 November 1940:
SubDiv 8 is assigned to SubRon 2, Sixth Fleet.

31 January 1941:
LtCdr (later Captain) Inaba Michimune (51)(former CO of I-121) is appointed the CO.

10 November 1941: Operation "Z":
Saeki Bay. I-6 is in Vice Admiral Shimizu Mitsumi's (former CO of ISE) Sixth Fleet under Rear Admiral (later Vice Admiral) Yamazaki Shigeaki's (former CO of OCA YAKUMO) SubRon 2 in Captain Takezaki Kaoru's SubDiv 8 with the I-4, I-5 and the squadron's flagship, I-7. LtCdr Inaba Michimune (former CO of I-121) is I-6's Commanding Officer.

Admiral Shimizu convenes a meeting aboard the Sixth Fleet's flagship, light cruiser KATORI. LtCdr Inaba and the other I-boat commanders are briefed on the planned attack on Pearl Harbor.

16 November 1941:
At 1300, I-6 departs Yokosuka for the Hawaiian Islands with ComSubDiv 8, Captain Takezaki Kaoru (former CO of I-5) aboard.

2 December 1941:
The coded signal "Niitakayama nobore (Climb Mt. Niitaka) 1208" is received from the Combined Fleet. It signifies that hostilities will commence on 8 December (Japan time). Mt. Niitaka, located in Formosa (now Taiwan), is then the highest point in the Japanese Empire.

7 December 1941: The Attack on Pearl Harbor:
Off Hawaii. SubRon 2 is arrayed to the northeast and northwest of Oahu. Its mission is to reconnoiter and attack any ships that try to sortie from Pearl Harbor. I-6 patrols off the northern entrance to Kaiwi (Molokai) Channel between I-4 and I-5.

9 December 1941:
Kauai Channel, SE of Pearl Harbor. At 0840, LtCdr Inaba sights a LEXINGTON-class aircraft carrier and two heavy cruisers N of Molokai, heading NE at 20 knots. Inaba attempts to attack the carrier, but is forced underwater and manages to report his sighting several hours later.

Kwajalein. At 1650 (JST), Vice Admiral Shimizu orders a total of 9 submarines to pursue the carrier (actually Vice Admiral Halsey's USS ENTERPRISE), thought to be heading for West Coast. I-6 remains in Hawaiian waters, but now shifts to S of Oahu.

27 December 1941:
A torpedoman, injured during a routine inspection of torpedoes several days earlier, dies of blood poisoning. His body is buried at sea.

9 January 1942:
270 miles NE of Johnston Island, I-18 of the Special Attack Force sights a LEXINGTON-class carrier, a heavy cruiser and two destroyers steaming westward. I-18 reports the sighting to Headquarters, Sixth Fleet. Rear Admiral Yamazaki orders all available I-boats in the area to form a picket line.

I-6 departs her patrol area to join the hunt for USS LEXINGTON (CV-2), detected by I-18. After I-1 develops a diesel trouble, I-6 replaces her in the picket line NE of Johnston Island.

10 January 1942:
Throughout the day, the lookouts sight US aircraft patrolling in the area on five separate occasions. Plotting their courses, the navigator of I-6 calculates the enemy carrier's probable position.

11 January 1942:
At 1841, while patrolling 270 miles NE of Johnston Island, I-6 sights a destroyer and crash-dives. Soon thereafter, a LEXINGTON-class carrier, one heavy cruiser and another destroyer appear on a southeasterly course at 19N, 165W. The carrier is USS SARATOGA (CV-3) of TF 14 under Rear Admiral Herbert F. Leary, steaming at 15 knots to rendezvous with USS ENTERPRISE (CV-6).

LtCdr Inaba fires three Type 89 torpedoes with three-second intervals from 4,700 yards. At 1915, one of them hits SARATOGA port amidships, flooding three of her boiler rooms and killing six firemen. The carrier heels first to starboard, then to port, taking on 1,100 tons of water and losing headway. Seven minutes after the hit the escorting destroyers commence a counterattack, but fail to locate the submarine, escaping at 330-feet depth. The soundman of I-6 reports two loud explosions, followed by a series of smaller detonations, interpreted as breaking-up noises. After 2200, LtCdr Inaba reports two hits on a LEXINGTON-class carrier, claiming her as probably sunk. [1]

SARATOGA is soon able to increase her speed to 16 knots and make it back to Pearl Harbor under her own power. As a result of subsequent repairs she is put out of the war for six months.

12 January 1942:
Departs her patrol sector for Kwajalein.

22 January 1942:
Arrives at Kwajalein with just 800 liters of fuel left.

24 January 1942:
I-6 departs Kwajalein for Japan.

2 February 1942:
I-6 arrives at Yokosuka. SubRon 2's boats undergo a refit and overhaul.

Early February:
Dry-docked at Yokosuka.

8 February 1942:
SubRon 2's I-1 through I-7 are assigned to Vice Admiral Takahashi Ibo's (former CO of KIRISHIMA) Netherlands East Indies Invasion Force in Rear Admiral (later Vice Admiral) Ichioka Hisashi's (former CO of YURA) SubRon 2. Reassigned to Southeast Area Unit.

13 February 1942:
The staff of SubDiv 8 is transferred to I-4.

14 February 1942:
Departs Yokosuka for Staring Bay, SE Celebes (now Sulawesi).

22 February 1942:
Arrives at Staring.

23 February 1942:
At 0700, departs Staring Bay on her second war patrol W of Sumatra in company of I-4 and I-5.

25 February 1942:
W of Timor. At 1230 (JST), when running on the surface, I-5 and later I-6 are spotted by a Mitsubishi C5M Type 98 "Babs", escorted by nine A6M Zeke fighters from the 3rd NAG Ambon detachment. Misidentifying both subs as Dutch, the fighters repeatedly strafe them. I-6 is forced underwater, but receives no damage.

8 March 1942:
Arrives at Penang.

16 March 1942:
Vice Admiral, the Marquis, Komatsu Teruhisa (former CO of CA NACHI) assumes command of the Sixth Fleet (Submarines). Vice Admiral Shimizu is reassigned later as the CINC, First Fleet.

26 March 1942:
Departs Penang to patrol in the Indian Ocean N of Maldive Islands and and W of Bombay on her third war patrol.

27 March 1942:
Berlin. The German naval staff requests the IJN to launch operations against Allied convoys in the Indian Ocean.

March 1942: Operation C - The Raids in the Indian Ocean:
Headquarters, Combined Fleet orders that the western coasts of India and Ceylon (now Sri Lanka) be reconnoitered before the commencement of Operation C." All of SubRon 2's boats, except I-I, are to participate in the operation.

31 March 1942:
Indian Ocean, off Eight Degree Channel. At 1635, LtCdr Inaba sights an enemy vessel and commences an approach. Just before firing his torpedoes, the target is identified as a hospital ship and the attack called off. I-6's target was most likely HMHS VITA en route from Addu. (Later, VITA picks up the survivors of carrier HMS HERMES).

2 April 1942:
Arabian Sea, 300 miles SW of Bombay. In the afternoon, I-6's lookouts spot 5,897-ton British steamer CLAN ROSS sailing independently from Liverpool to Cochin with 3,655 tons of general cargo and 1,027 tons of explosives. The submarine closes at high speed and submerges in a favorable position.

LtCdr Inaba fires two torpedoes from 1,640 yards, scoring one hit port amidships. At 1414, CLAN ROSS goes down by the stern at 15-58N, 68-24E. 11 sailors are lost, 3 injured.

I-6 surfaces again to question the survivors. Her medical officer provides them with water and biscuits and gives them the bearing to Bombay. Before departure, the off-duty crew lines up on the afterdeck and salutes the survivors, wishing them a "Bon Voyage!" in broken French.

The survivors from CLAN ROSS are later rescued by Norwegian armed motor merchant L.A. CHRISTENSEN and a native Indian vessel.

5 April 1942: Operation "C":
Vice Admiral Nagumo Chuichi's Carrier Striking Force ("Kido Butai") attacks the British naval base on Colombo, Ceylon (now Sri Lanka). They wreck the base's facilities, destroy 27 aircraft and sink several ships. A floatplane finds Vice Admiral (later Admiral of the Fleet/Sir) James Somerville's Eastern Fleet's cruisers HMS CORNWALL and DORSETSHIRE at sea. Nagumo's airmen sink both ships, but are unsuccessful in their search for the rest of Somerville's fleet.

7 April 1942:
Arabian Sea, 170 miles NW of Bombay. Around 1600, when I-6 prepares to shift to a different position, her lookouts sight 5,424-ton British merchant BAHADUR, independently on a voyage from Bombay to Basra with 5,100 tons of government stores, including ammunition. LtCdr Inaba dives and fires a spread of torpedos, but their wakes are spotted by the merchant, which evades with a sharp turn to starboard, then opens the range at flank speed. I-6 fires two torpedoes from aft tubes, but misses again.

The submarine surfaces and commences a tail chase. At 6,570 yards I-6 opens fire with her 5-inch deck gun, but it jams after the first shot. When the submarine submerges, ready to abandon the hunt, BAHADUR suddenly stops to lower her boats. I-6 closes in and fires two more torpedoes from port beam. At 1920, BAHADUR goes down by the stern at 19-44N, 68-28E. Her crew is later rescued by US ship VOLUNTEER.

9 April 1942: Operation "C":
Nagumo's Striking Force attacks the British naval base at Trincomalee, Ceylon. They wreck the base's facilities and shoot down nine planes. A floatplane spots old light carrier HMS HERMES and Australian destroyer HMAS VAMPIRE 65 miles S of the base. The Striking Force sinks both. Nagumo's aircraft also find and sink several smaller ships.

10 April 1942:
Arabian Sea, 300 miles SW of Bombay. After 0815, I-6 battle-surfaces on two 150-tons dhows and shells them, reporting both as sunk. On that same day, I-6 is reassigned to the Advance Unit.

17 April 1942:
Arrives at Seletar, Singapore.

21 April 1942:
Deperts Singapore for Yokosuka in company of I-5.

1 May 1942:
Arrives at Yokosuka. Undergoes upkeep and repairs until 6 June.

23 May 1942:
LtCdr (later Cdr) Nakamura Shozo (54)(former CO of I-153) is appointed the CO.

5 June 1942: Operation "AL"- The Invasion of the Western Aleutians:
Twenty ships of Vice Admiral Hosogaya Boshiro's (former CO of MUTSU) Fifth Fleet, including light cruisers KISO and TAMA, three destroyers, three corvettes, three minesweepers and four transports land Rear Admiral (later Vice Admiral) Omori Sentaro's (former CO of HYUGA) Occupation Force on Attu, Aleutians without opposition.

7 June 1942:
Captain (later Rear Admiral) Ono Takeji's Occupation Force takes Kiska without opposition.

10 June 1942:
Reassigned to the Northern Unit with I-1, I-2, I-3, I-4, I-5 and I-7.

17 June 1942:
Departs Yokosuka for the Aleutians in company of I-1, I-2, I-3, I-4 and I-7 on her fourth war patrol. Joins the K patrol line patrolling in Unimak Pass area.

20 June 1942:
Departs Yokosuka for the Aleutians.

7 July 1942:
Ordered to proceed to the Kiska area.

20 July 1942:
SubRon 2 is ordered to return to Japan, except I-6 is ordered to remain as the patrol submarine of the Northern Force in the Kiska area.

29 July 1942:
A Kawanishi H6K "Mavis" flying boat of Toko NAG Kiska detachment reconnoiters Atka Island and reports the presence of an American seaplane tender in Nazan Bay. I-6 proceeds there, but finds nothing.

7 August 1942:
Rear Admiral William W. Smith's TG 8.6 shells Kiska. I-6, RO-61, RO-64 and RO-68 anchored in the harbor crash-dive to escape damage. After the bombardment, some of the submarines are sent to intercept the task group, but they fail to overtake the Americans.

15 August 1942:
I-6 is ordered to return to Yokosuka and departs Kiska.

20 August 1942:
SubRon 2 and SubDiv 8 are disbanded. I-6 and I-5 are reassigned to SubDiv 7.

23 August 1942:
Arrives at Yokosuka for overhaul. I-6 is converted to carry a waterproofed Daihatsu landing barge.

25 August-1 December 1942:
LtCdr Nakamura is appointed the CEO of I-180 as additional duty.

22 October 1942:
Captain (later Vice Admiral) Mito Hisashi (former CO of KATORI) assumes command of SubRon 1.

15 December 1942:
LtCdr (Cdr, posthumously) Izutsu Monshiro (57)(former CO of I-153) is appointed the CO.

16 February 1943:
At 1000, departs Yokosuka for Truk, carrying a Daihatsu barge.

23 February 1943:
At 1015 arrives at Truk. Later that day she is inspected by ComSubDiv 7.

26 February 1943:
Embarks ammunition, fuel and provisions from HIE MARU. The Daihatsu barge is debarked.

28 February 1943:
Departs the anchorage for a test cruise off Uman Island at 0800, returning by 1500.

February 1943:
Rear Admiral Mito issues SubRon 1 Secret Order No. 1 that orders I-6 to advance off shore from Brisbane, lay magnetic mines and thereafter carry out communications destruction warfare in that area until returning to Truk in late March.

2 March 1943:
At 1600 departs Truk for the Brisbane area on her fifth war patrol, carrying nine German TMC type magnetic mines. [3]

4-5 March 1943:
Transits St. George's Strait heading south.

8 March 1943:
FRUMEL (Fleet Radio Unit, Melbourne) signals intelligence unit decodes a Japanese message about the departure of I-6. [4]

11 March 1943:
By 1200, I-6 arrives within 60 miles NE of Brisbane. At 1715 LtCdr Izutsu sights a 10,000-ton merchant and commences an approach. At 1844 he fires two torpedoes; both miss.

12 March 1943:
Reconnoiters Moreton Bay, Caloundra Head and the approaches of Brisbane.

13 March 1943:
NE of Caloundra Head (noon position 26-42S, 153-20E). From 1850 to 1914, I-6 lays all nine mines within 6 miles from the coast to the depth of 24-34 meters and then heads back to sea. [5]

14-16 March 1943:
Patrols in the area between Stradbroke and Fraser Islands.

17 March 1943:
SE of Sandy Cape (noon position 25-49S, 153-49E). At 1430, Izutsu sights the two-ship convoy B.T.44 escorted by HMAS GYMPIE. At 1507 he fires two Type 89 torpedoes at American merchant CHARLES C. JONES. Four minutes later two wakes pass within 20 yds astern of that ship. Both CHARLES C. JONES and JOSEPH HOLT open fire from their deck guns to alert HMAS GYMPIE.

An Avro "Anson" of RAAF No. 71 (Reserve) Squadron on an anti-submarine patrol over the convoy spots the torpedo wakes and drops a sea marker to the presumed location of the submarine. GYMPIE and the "Anson" commence a search, lasting until 1530. At 1532, the patrol plane piloted by Sgt. R.N. Walesby drops one depth charge.

I-6 escapes the chase without any damage. At 2022 that evening, she sends a situation report (Secret Message No. 171832) to Truk, which is partially intercepted by FRUMEL station. Two US patrol craft are dispatched to the presumed location of I-6, searching her until sunset on 18 March.

March 1943:
After the Battle of the Bismarck Sea, the Sixth Fleet decides to resume the supply runs to Lae. I-5, I-6, I-16 and I-20 are temporarily attached to the HQ, Eighth Fleet for this purpose.

21 March 1943:
Off Cape Byron. In the morning, I-6 is ordered to return to Rabaul. That evening, at 1933, she sends another situation report (Secret Message No. 211733) to Truk, which is intercepted by FRUMEL.

27 March 1943:
At 0730, arrives at Rabaul.

29 March 1943:
Reassigned to South-East Area Fleet.

3 April 1943:
Departs Rabaul for for her first supply run to Lae, New Guinea with 3.3 tons of weapons and ammunition, 22 tons of clothing, 15.4 tons of food in 77 supply drums and 30 passengers.

5 April 1943:
Arrives at Lae, where the cargo is transferred to Daihatsu barges. I-6 embarks 29 passengers, including four soldiers of the 41st Infantry Regiment, returning the unit's flag to Rabaul. Soon after her departure from Lae, I-6 sights enemy torpedo boats, but manages to crash-dive in time.

7 April 1943:
Returns to Rabaul.

11 April 1943:
Arrives at Lae on her second supply run, carrying 4.4 tons ammunition and weapons, 19 tons clothing, food in 77 supply drums and 26 passengers. Departs for Rabaul with 42 passengers.

17 April 1943:
Arrives at Lae on her third supply run, carrying 4 tons ammunition and weapons, 17 tons clothing, 77 supply drums and 28 passengers. Departs for Rabaul with 39 passengers. After departure from Lae sights enemy torpedo boats near Tami Islands and evades them underwater.

21 April 1943:
I-6 is reassigned on paper to the Northern District Force, Fifth Fleet to reinforce and resupply the isolated Japanese garrisons in the Aleutian Islands.

24 April 1943:
Arrives at Lae on her fourth supply run, carrying 1 ton of ammunition, 16 tons clothing, 16 tons of food in supply drums and 20 passengers. Returns to Rabaul with 42 passengers.

30 April 1943:
Arrives at Lae on her fifth supply run, carrying 3 tons of ammunition and weapons, 19 tons of clothing, 1 ton of food in supply drums and 30 passengers. Returns to Rabaul with 41 passengers. At dawn, sights enemy torpedo boats and spends one hour evading them.

7 May 1943:
Arrives at Lae on her sixth supply run, carrying 2.8 tons of weapons, 4 tons of artillery shells, 13 tons of clothing, 77 supply drums and 10 passengers. Returns to Rabaul with 12 passengers.

11 May 1943: American Operation "Landcrab"- The Invasion of Attu, Aleutians:
Rear Admiral (later Admiral) Thomas C. Kinkaid Task Force 16, covered by Rear Admiral Francis W. Rockwell's Task Force 51, lands the Army's Seventh Division that captures Attu Island.

13 May 1943:
Arrives at Lae on her seventh supply run, carrying 11.5 tons of weapons, 5 tons of ammunition, 9 tons of food in supply drums and 10 passengers. Returns to Rabaul with 4 passengers.

Five miles off Lae. Cdr Morton C. Mumma, Jr. (former CO of SAILFISH), ComTGp 50.1, is riding in Lt (jg) R. E. Hamachek's PT-150. Hamachek and Ens H. P. Knight's PT-152 spot a submarine, probably I-6, on the surface making about 12 knots at 6,000 yards. Each PT fires two torpedoes at long-range. The submarine stops and all the torpedoes pass ahead of her. Closing to 4,000 yards, PT-150 fires one torpedo at the stationary target. Suddenly, the submarine increases speed and the torpedo misses astern. The PTs run parallel to the submarine's course and then turn to decrease the range, but the I-6 crash-dives. As the PTs lay to, the submarine fires a torpedo that passes under the bow of PT-150. She is saved only by her shallow draft.

14 May 1943:
I-6, and later I-5, are diverted to rescue the crews of Mitsubishi G4M Betty bombers of the 751st NAG downed during the raid on Oro Bay. I-6 locates and rescues two fliers in the area 60 miles off Buna.

20 May 1943:
LtCdr (Captain, posthumously) Shimose Kichiro (58)(former CO of I-162) is appointed the CO.

21 May 1943:
Arrives at Lae on her eighth supply run, carrying 5.1 tons of weapons, 5.4 tons of ammunition, 4.6 tons of food and 31 passengers. Returns to Rabaul with 40 passengers.

That same day, Imperial General Headquarters decides to evacuate the garrison at Kiska Island, Aleutians.

26 May 1943: Operation KE-GO:
The evacuation from Kiska to Paramushiro Island in the Kuriles via submarines begins. Thirteen I-boats are eventually involved in the operation that extricates 820 men. Three submarines are sunk and three others are damaged.

28 May 1943:
Arrives at Lae on her last (ninth) supply run, carrying 18 tons of food, 4.3 tons of weapons and medicine, 2 tons of clothes, a Daihatsu barge and 23 passengers. Returns to Truk without embarking any passengers.

31 May 1943:
I-6 and I-5 are reassigned to Sixth Fleet.

1 June 1943:
Arrives at Truk.

2 June 1943:
Departs Truk for Yokosuka.

8 June 1943:
Arrives at Yokosuka. Undergoes repairs and maintenance.

1 July 1943:
Departs Yokosuka to support the evacuation of the Kiska garrison. SubDiv 7 is reassigned to Fifth Fleet.

2 July 1943:
Departs Yokosuka for Paramushiro to support the evacuation of the Kiska garrison on her sixth war patrol.

15 July 1943:
Rear Admiral Kouda Takero (former CO of CHOKAI), ComSubRon 1, orders resumption of the evacuation of troops from Kiska.

17-19 July 1943:
Patrols NNE of Kiska in company of I-5. On three separate occasions they spot three American destroyers, but are unable to attack.

28 July 1943: Operation KE-GO:
The Japanese complete the evacuation of Kiska.

4 August 1943:
Arrives at Paramushiro.

16 August 1943:
Departs Paramushiro to raid enemy communications off Kiska on her seventh war patrol.

3 September 1943:
Returns to Paramushiro.

5 September 1943:
Departs Paramushiro for Yokosuka.

10 September 1943:
Arrives at Yokosuka. Undergoes repairs and maintenance.

25 October 1943:
Reassigned to South-East Area Fleet.

30 October 1943:
Departs Yokosuka for Rabaul to participate in supply missions to Sio, New Guinea, and Iboki plantation, New Britain.

16 November 1943:
Arrives at Sio on her first supply run to that location.

4 December 1943:
Arrives at Sio on her second supply run.

18 December 1943:
Arrives at Sio on her third supply run. When disembarking her cargo, I-6 is attacked by aircraft and returns with some cargo still aboard.

27 December 1943:
Arrives at Sio on her last (fourth) supply run to that location. Early morning, after her mission, I-6 is sighted by torpedo boats and depth-charged. Later, she is attacked by aircraft, but escapes without damage.

On the same day, an enemy convoy is spotted off Cape Gloucester. I-6, carrying only two torpedoes, is ordered to intercept it.

28 December 1943-1 January 1944:
Patrols in the Dampier Strait in search of enemy shipping.

2 January 1944: American Operation "Michaelmas"- The Invasion of Saidor, New Guinea:
Rear Admiral (later Vice Admiral) Daniel E. Barbey's Task Force 76 lands the Sixth Army's 126th Regimental Combat Team of the 32d Division at Saidor and by-passes the Japanese garrison at Sio, 75 miles east.

4 January 1944:
Departs Rabaul on her first supply run to Iboki Plantation.

6 January 1944:
Arrives at Iboki, unloads her cargo, then departs for Rabaul.

10 January 1944:
Returns to Rabaul.

17 January 1944:
Departs Rabaul on her second supply run to Iboki.

19 January 1944:
Arrives at Iboki, unloads her cargo, then departs for Rabaul.

21 January 1944:
Returns to Rabaul.

28 January 1944:
Departs Rabaul on her third supply run to Iboki, carrying troops, but no supplies.

30 January 1944:
Arrives at Iboki, unloads her cargo, but damages her screws on a reef N of the anchorage, not marked on the IJN maps.

1 February 1944:
Returns to Rabaul. On that same day SubDiv 7 is directly attached to Sixth Fleet HQ.

3 February 1944:
Departs Rabaul on her first supply run to Sarmi.

5 February 1944:
Receives is ordered to return to Yokosuka.

13 February 1944:
Departs Rabaul on her first supply run to Lorengau, Manus, carrying 12 heavy machine guns and their ammunition.

17 February 1944:
Arrives at Lorengau, unloads her cargo, then departs.

29 February 1944:
Arrives at Yokosuka for an overhaul.

30 April 1944:
Lt (promoted LtCdr 1 May; Cdr, posthumously) Shinohara Shigeo (62)(former CO of I-169) is appointed the CO.

12 May 1944:
Captain Hori Takeo (50) (currently serving as instructor at the submarine and navigation schools) is appointed the CO of I-6 as additional duty.

27 May 1944:
LtCdr (Cdr, posthumously) Fumon Shozo (63)(former CO of RO-49) is appointed the CO.

13 June 1944: Operation A-Go - The Defense of the Marianas:
Admiral Toyoda Soemu (former CO of HYUGA), CINC, Combined Fleet, orders Vice Admiral Takagi Takeo (former CO of MUTSU), CINC, Sixth Fleet to redeploy his submarines to the Marianas. From his headquarters on Saipan, Takagi orders all available submarines to deploy E of the Marianas.

15 June 1944: American Operation "Forager" - The Invasion of Saipan:
Vice Admiral (later Admiral) Richmond K. Turner's Task Force 52 lands Marine LtGen Holland M. Smith's V Amphibious Corps and the invasion begins. Communications between Takagi's Advance Expeditionary Force (Sixth Fleet) are disrupted by the invasion. Command of the Sixth Fleet's submarines passes to Rear Admiral Owada Noboru (former CO of YAMASHIRO), ComSubRon 7 at Truk.

16 June 1944:
I-6 departs Yokosuka for Saipan.

NE of Hachijo-Shima. The 5,123-ton freighter TOYOKAWA MARU (ex-BANGOR), chartered from Matsuoka Kisen Line of Kyoto, departed Ogasawara (Bonin) Islands on 14 June en route to Yokosuka in convoy No. 3606, comprising four marus, kaibokans AMAKUSA, NOMI, OKI and converted subchaser SHOWA MARU No. 7.

At 2233, TOYOKAWA MARU sights a submarine surfacing near the convoy. A submarine alert is given. TOYOKAWA MARU makes a sharp turn and rams the submarine's starboard side slightly abaft the conning tower. The submarine takes on a heavy list, turns turtle and sinks in a few minutes. TOYOKAWA MARU opens fire with machine guns and drops some depth charges. There are no survivors of I-6's crew of 104.

1 July 1944:
After the rescue attempts of I-10 and I-38 fail, I-6 is ordered to evacuate Vice Admiral Takagi and his 6th Fleet staff from their headquarters on the eastern coast of Saipan, but LtCdr Fumon does not acknowledge the order. The IJN presumes I-6 is MIA from this date.

3 July 1944:
Sixth Fleet HQ makes another unsuccessful attempt to contact I-6.

10 September 1944:
Removed from the Navy List.

Authors' Notes:
[1] A popular anecdote suggests that for hitting that carrier, I-6's torpedo officer received a bonus of beer from Admiral Yamamoto, but this is not confirmed by survivors from the submarine.

[2] According to the 1954 "British Naval Staff History" on 31 March the 4,672 ton SS CLAN MACINNES was unsuccessfully attacked by a submarine believed to be co-operating with a dhow in the Eight Degree Channel in 07-48N, 73-30E.

[3] Australian naval historian and author David M. Stevens has identified the mines as TMB ground influence mines. The details given in the Japanese sources (including I-6s War Diary), however, clearly suggest that the correct type was TMC.

[4] In all likelihood it was I-6's Secret Message No. 021201, first transmitted at 1241 (JST) on 2 March.

[5] The mines laid by I-6 were first discovered by the sloop HMAS SWAN on 24 March, when two of them self-detonated during target practice in that area. The area was repeatedly swept until September that year, but only one mine was detected as a result.

Thanks go to Dr. Higuchi Tatsuhiro of Japan. Special thanks for help with the revisions go to fellow IJN submarine enthusiast Steve Eckhardt of Australia and Rob Stuart of Canada.

Bob Hackett and Sander Kingsepp.

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