KD5 (I-I65) class submersible (1929)

Japan 1934-45: I-65/165, 66/166, 67/166 large oceanic submarines.

The Kaidai V type (“Navy large type V”) or I-65-class (海大5型) Kaidai-go-gata, Project number S29, built under the 1923-1928 programme, had only I-165, I-166, and I-67 which construction, all completed in 1932. The design was an upgrade with a new deck gun going from 50 caliber to 65-caliber and still dual-purpose. The hull was made slightly wider and taller, with a large crew at 75 and the pressure hull was reinforced in order to reach a service depth of 230 ft (70 m). I-165 was modified at the end of the war, converted as a Kaiten carrier but none of these three submarines survived the war: I-67 was lost with all rew in an exercise in 1940, I-165 on 27 June 1945 off East Saipan in her first Kaiten mission, and I-166 by HMS Telemachus on 17 July 1944 off the coast of Singapore.

Development of the Kaidai V

Hirootoko’s Colorization of the I-65 on trials in Hiroshima Bay, 1932.

The Kaichū Type were the “big boys” among IJN submarines, they were essentially cruiser submarines inspired by 1918 German cruiser types like the U-142 class, from plans obtained as war reparation after 1918. This allowed Japanese engineers to find their own way in this long range design for fleet submarines. The KD1 and KD2 were only moderately successful when planned in 1919 but the KD3 was a more mature design, more reliable for long range fleet operation, reocnnaissance and fleet interdiction up to the Hawaiian and Guam waters. They were the “long range underwater arm” for the IJN across the Pacific to protect Japan. It was impreative for them to have a high surface speed and heavy armament inrder to feet in fleet operations.

The Kaidai 5 were based on the Project 28 submarines of Kaidai IV, planned in 1927 to be more agile and faster while having the same output. The Japanese staff wanted improved performances across the board. The Kaidai IV were still planned for for long-range reconnaissance, catch an enemy naval forces underway to Japan, or taking part in a long war of attrition over lines of communications across the Pacific. They were to prey first and foremost on enemy warships, expecially after the tonnage reduction after 1922 from the Washington Treaty. US battleships were above all else, prime targets for the Kaidai, to reduce US capital ship superiority. They had powerful advocates within the IJN, the “submarine faction”. It hey had won the debate in 1939 over Yamamoto, the Pearl Habout Attack would have been rather a massive submarine ambush out of the few entrances and channels to Pearl Harbour instead of a massive air attack. They still were conceded a submarine attack on the harbour, but with midget subs. Given their mediocre results, the Japanese could thank Yamamoto for his foresight. Kaitens were to roam the waters also of Guam, Midway and the Philippines.

The Kaidai V changes in a nutshell

These three vessels were built under the 1927 fiscal year budget, completed in 1932. Design designation was S29. As an improved version of the Kaidai Type IV, the hull shape was completely redesigned to achieve a greater propulsion efficiency. They were equipped with the same Sulzer-type diesel engines of the Type IIIb, yet their surface speed increased by 0.5 knots thanks to new camculations and reshaping of the puter hull. So this was seen as a half success (an increase of 1 knot was expected). The armament also underwent significant changes with a main gun having a new high angle mount for the 10 cm gun with a 65 caliber barrel, intended for both surface and anti-aircraft use, against heavy bombers the US were believed to possess in numerous bases in case of war. The AA armament wsas further boosted by the adoption of 12 mm Type 92 heavy machine guns, and the K-Tube hydrophone suite replaced by the newly developed MV-type hydrophone, imported from the United States. The torpedo armament remained unchanged, but the torpedo tubes were updated to a bubble-less discharge type to emit less sound when firing, fearful of a sonar detection by the enemy.

Construction

On May 20, 1942, all three were redesignated with a third number in the 100 series due to a reboot of numbers, thus I-65 became I-165 and else. When Completed on December 1, 1932 at Kure Naval Arsenal where they were fitted out.
I-165 (ex-I-65) was built at the Kure Naval Arsenal, laid down on 19 December 1929, launched on 2 June 1931 and completed on 1 December 1932: Four years construction (Sank on June 27, 1945, after being bombed by aircraft off the Mariana Islands).
I-166, was ordered as I-66 at Sasebo Naval Arsenal, laid down on 8 November 1929, launched on 2 June 1931 and completed on November 10, 1932: Also four years and she preceded I-65 but was not retained as class leader. She was sunk on July 17, 1944 in the Strait of Malacca after being ambushed by the British T-class submarine Telemachus.
I-167, ordered as I-67 from Mitsubishi, Kōbe Shipyard on 8 November 1929, launched on 2 June 1931 was completed on August 8, 1932, so a bit less than four years, but that was still very long for submarines for western standards, even in peacetime. She had the shortest carrer, sinking on August 29, 1940, after executing a crash dive during training that turned awry (see below).

Design of the KD-V class

Hull and general design

I-65 and her sisters displaced 1,732 tonnes (1,705 long tons) surfaced and 2,367 tonnes (2,330 long tons) submerged, comparable to previous boats, with an overall length of 97.7 m (320 ft 6 in), a beam of 8.2 m (26 ft 11 in) and a draft of 4.7 m (15 ft 5 in). The hull derives from the I-61 and I-64 in great lines, but with increased thickness for the pressure hull for a diving depth ported from 60 metres (197 ft) to 75 meters (246 ft) and around 110m+ for the crushing limit. Engineers further maximized internal volume thanks a revised better cross section on top of a greater beam, compared to 7.80 m (25 ft 7 in), and still slightly trapezoidal in section. They keep their anti-submarine net cutter at the bow, O-ring for towing, but the bow shape was again revised albeit details are scarce. There are no plans around and nothing to really pinpoint the hull shapes changes with precision. They however kept the same two anchors in recesses forward, two foward diving forward planes aft of the anchors, also in horizontal recesses and of the same shape. The main gun was the same as previous models, still protected by a breawater platform, sponsoned over the sides to reduce seawater spray.

The conning tower was also roughly similar, with the same well profiled “foot” at its base, same enclosed helmsman post with windows forward, same open navigation platform further aft. They carried three periscopes, two for watch of different size, one for long range, more visible, one for close approaches, smaller, and one for attack. The aft section of the conning tower was open, with now a pintle of a 12mm AA HMG located there. There was also a signal mast and one at the end of the deck, flying the Rayonned Hinomaru of the Navy. Exhausts were located there too and the upper rudder aft was protected by a guard bar.

Powerplant

I-65 and sisters rconstructed the same powerplant as the KD-3 and KD-4: Their Type 3 Kampon models were derived not from older Sulzer diesels, but Reischenbach Mk 2 diesel engines rated for 6,000 hp (4,474 kW) combined on a smaller, lighter package overall. They were 6-cylinder, 4 valve models reminiscent of those fitted on the U-139 cruiser submarines. They drove two shafts, then two fixed-pitch 3-bladed propeller shaft, for speeds up to 20.5 knots (38 km/h; 23 mph) a bit more than the KD4/KD-3 types, and carried 230 tons fuel for a range of 10,000 nmi (roughy 19,000 km; 12,000 mi) at 10 knots (19 km/h; 12 mph) like the KD3 but less than the KD4. Underwater, they ran on two Siemens Electric motors rated for 1,800 hp (1,342 kW). Top speed underwater was a hit less than on the KD-4 better at 8.2 knots (15.7 km/h; 9.8 mph), underwater range however was 60 nmi (110 km; 69 mi) at 3 knots (5.6 km/h; 3.5 mph). (90 nmi/170 km; 100 mi for the KD3s).

Armament

I-65 and sisters of the KD-V retained the same armament as the previous KD-4, six 533mm torpedo tubes, four forward, and two aft (and 14 total, so 8 in storage). They counted much on their new 100mm/60 (4″) dual-purpose deck gun for most of her antiship work. However if this new gun was a potent defender against AA bombers, agains ship it lacked punch due to a smaller HE shell, albeit this was compensated for a much greater muzzle velocity. Some sourrces however states they also kept their original 120 mm/45 as previous Kaidai classes.

100cm/50 Type 88 deck gun (1928)

The 10 cm/50 Type 88 naval gun was a dual-purpose model that existed in two variants:
-One variant had a removable barrel liner
-The other had an autofretted monoblock barrel.
Both variants had horizontal sliding block breaches, hydro-pneumatic recoil mechanism, Fixed Quick Fire ammunition. They were mounted on HA/LA central pivot mountswith up to 90° elevation. The theoretical rate of fire of 12 rounds per minute was limited to half this due to the speed of the pneumatic shell hoist (and training). This was the shining uniquely new deck gun aboard I-165 class Type KD5 submarines of the Imperial Japanese Navy. It was never used on other subs.
Specs:
Mass 2,830 kg (6,240 lb), length 5.3 m (17 ft 5 in), barrel 5 m (16 ft 5 in)
Shell: Fixed Quick Fire 100 mm x 380 mm 13 kg (29 lb) 100 mm (3.9 in)
Breech: Horizontal sliding block, recoil Hydro-pneumatic. Central Pivot mount -7° to +90°, 2×150° traverse
Muzzle velocity 885–895 m/s (2,900–2,940 ft/s), efective range 11,200 m (36,700 ft) at +90°, max 16.2 km (10 mi) at +45°. 1

Type 6 533mm Torpedo

The KD-V had four tubes in the bow and reloads for each, plus two in the stern and two reloads, for fourteen total of the 6th Year Type torpedoes, the first type using metric measurements. This model was designed at the brand new Imperial Japanese Navy Technical Department, favoring a rule era naming scheme. Development started in 1914, completed in 1917 for a service in 1918 on both surface ships and submarines. Originally defined in the Eight-Eight Program replacing the 18-in by a 21-inch caliber torpedo and planning a 61 cm (24-inch) Type 8. This went with the decision to switch to metric units. In 1922, the Washington Naval Treaty was signed by Japan and forbade any caliber besides 550 mm (French standard) and the international norm remained at 53 cm.

The 1,432 kg (3,157 lb), 6.84 m (22.4 ft) Type 6 was powered by a Wet heater to bring its 203 kg (448 lb) Shimose warhead at 7,650 m (4.13 nmi) at 36 knots (67 km/h) ot 10,000 m (5.4 nmi) at 32 knots (59 km/h), 15,000 m (8.1 nmi) at 26 knots (48 km/h). These were above average performances already compared to other Navies for that caliber. It’s possible they tested the Type 89 in the 1930s, however the latter was only carried by the Junsen and Kaidai-type submarines. They could reach 45 knots. They could also have tested or deployed the Type 92 electric torpedo, leaving no trail (more data on later posts).

Type 92 Heavy machine gun

Instead of a Type 3 pintle-mounted 8 mm LMG, AA defence was upgraded to the Type 92, 12 mm (0.48 in) heavy MG, the same used by the Army. It was a hefty beast 55.3 kg (122 lb) without the mount and needed 2-3 men to have it unpacked and installed when surfaced. It measured 1,156 mm (45.5 in) for a barrel length of 721 mm (28.4 in) and firing a cartridge 7.7×58mm Type 92. Gas-operated the rate of fire was 450–500 rounds per min for a muzzle velocity of 780 m/s (2,600 ft/s). Effective firing range however was only good against low(flying strafing aircraft back in 1930, at 800 m (870 yd) for a maximum firing range of 4,500 m (4,900 yd). The Feed system comprised 30-round Hotchkiss-type metal strip.
Indeed, this machine gun was historically a scaled-up version of the Type 3 heavy machine gun, calibre 7.7 mm, air cooled, ammo strip-fed, based in turn on the Hotchkiss M1914. The air cooling imposed a series of metal rings. It was coupled with a ring-type anti-aircraft sight as well.

Sensors

These KD-IV had a pair of hydrophones of the MV-Chubu type echo-sounder, more modern as seen above than the K-Chubu. Other equipments included a ratio transmitter special 4 and 2 receiver RDF-T4. They also had degaussing equipment with three 3/8 inch coils directly below deck and two fitted on the sail like her sister.

⚙ I-61 specifications
Displacement	1,575 long tons surfaced, 1705t normal, 2,330 tons submerged, fully loaded
Dimensions	97.70 x 8.2 x 4.70m ()
Propulsion	2x Kaigun diesels: 6,000 bhp surfaced. 2 EM, 1,800 shp submerged
Speed	20.5 knots surfaced (38 kph), 8.2 knots (16 kph) submerged
Range	c230 tons fuel, 10,000 nm/10 kts surfaced, 60 nm/3 kts submerged
Armament	6× 533 mm TTs (4 bow, 2 stern, 14), 1x 120 mm/60 DP deck gun, 1x 12mm Type 92 HMG AA.
Test depth	75 m (246 ft)
Sensors	MV type Hydrophones
Crew	62

Career of the KD-V class

All three formed a single submarine division, at first assigned to the Sasebo Naval District, designated the 30th sub.div. in accordance with that district’s numbering system. It was formed on November 10, 1932, with I-67 (registered to the Kure Naval District) and I-66 (registered to the Sasebo Naval District). I-65 completed later despite bing the lead boat, was subsequently incorporated. I-67 was lost in an accident on August 29, 1940 and the remaining two took part in the Pacific War. After taking part in the Malayan Campaign, they operated primarily in the Indian Ocean and yook part in the Battle of Midway. The division was disbanded on March 25, 1944. They had been reslatively successeful in commerce raiding, notably one sinking the Dutch submarine K XVI. Subsequently, I-166 was sunk in action in 1944. I-165 in 1945 was converted for, and took part in a Kaiten (manned suicide torpedo) attack mission near Saipan, in which she was sunk. I-165 sank eight merchant vessels in a Japanese “wolf pack” with I-20, which also sank eight vessels, so she ranks 5th among WW2 Japanese submarines in terms of kills.

I-65/165 (1931)

Completed on 1 December 1932, Lt.Cdr. Hankyu Sasaki was her first commanding officer, assigned to Submarine Division 30. On 20 August 1941, Lt Cdr Harada Hakue was her new CO. She was part of the 5th Submarine Squadron and her first patrol was on 8 December 1941 for Operation E, the invasion of Malaya. She also operated with I-166 of SubDiv 30, I-162, I-164 from SubDiv 29. SubDiv 30 was indeed reduced by the loss prewar of the I-167 in a diving accident. All four were ordered to patrol the South China Sea and took positions along a line 50 miles (80 km) east of Trengganu in Malaya to spot and intercept traffic. At 14:15 hours near Poulo Condore Island, I-65 reported Force Z (HMS Prince of Wales and HMS Repulse).

On 13 December 1941 she covered the landings on North Borneo. On 9 January 1942 while in the Java Sea she spotted and torpedoed, then finished off by shelling the 1,003-ton Dutch steamship Benkoelen from Soemenep to Cheribon. On 14 January 1942 at 02:17 in the Indian Ocean, west of the Mentawai Islands, she torpedoed and sank the 5,102-ton RIN AMC Jalarahan from Singapore to Calcutta. She returned at her base at Penang on 20 January 1942, first to arrive. Her 3rd patrol started on 5 February. On the 28th she torpedoed and damaged the converted boom carrier Laomedon, 45 miles SE of Ceylon. On 15 February pushing as far as the Arabian sea, she torpedoed and sank the 4,681-ton Johanne Justesen. On 20 February back in the Indian Ocean, she torpedoed and sank the 5,280-ton British merchant Bhima and missed another on 21 February. On 20 May she learned she has been renamed I-165. She was ordered for her 4th patrol to Kwajalein on 24 May and take part in the Battle of Midway north of Kure. On 30 June her new CO Torisu Kennosuke was appointed. On 10 July she was reassigned to the Southwest Area Fleet and entered Penang on 6 August for a 5th patrol of the Indian Ocean, starting 11 August.

On 25 August she spotted, torpedoed and sank the 5,237-ton AMC HMS Harmonides. She however soon experienced storm damage, forced back to Penang and managing to avoid detection by a flying boat and a RN destroyer on the way until arrival on 31 August. She left for her 6th patrol on 16 September for a spec ops, with 5 Indian National Army insurgents, to be landed on the north-west coast of India for sabotage and intel missions as well as to rally support. On the way, she torpedoed and sank the US armed freighter Losmar and claimed another unidentified merchant a day later. She arrived 5 miles (8.0 km) off the coast of Gujarat, west of Junagadh on 28 September after sunset and her insurgents sailed to shore with an inflatable. She then returned to Penang.
In November-December her new base became Surabaya. The IJ staff were weary of a possible landing on Timor that never happened. So she returned to Penang. In January 1943 she was sent to shell Geraldton, Western Australia, as a diversionary mission during the evacuation of troops through the Sunda Strait. Hiwever enemy activity was such it was decided instead to attack Port Gregory. Instead she shelled the local fish cannery for an ammunition plant from 16 km (9.9 mi) range with little effect and returned to Surabaya on the 16th.
On 25 May under her new CO LtCdr Shimizu Tsuruzo she departed on 9 October as per the 8th Submarine Squadron for an uneventful mission but on 16 December, while underway from Singapore to Penang she was attacked by an uknown Allied submarine (missed) and arrived on 18 December 1943.

On 18 March she spotted and torpedoed the British 3,916 GRT APC Nancy Moller from Durban to Ceylon. She was loaded with coal and was ordered to alter course east to avoid an area south-southwest of Ceylon where I-162 already sank SS Fort MacLeod on 3 March. But this brought her in I-165′s jaw. Both torpedoes hit on her port side and she likely borke in three and sank in less than a minute. Some survivors on four life rafts saw her killer surfacing 50 yards (46 m) from one lifeboat. I-165’s officer then called out for the captain and chief engineer but had no response. One raft was captured and the crew interrogated, they claiumed as told to day both died in the sinking. Gunlayer Dennis Fryer became POW and the other 5 men were killed, one Chinese sialor shot, the other loaded and pushed overboard to drawn. Then the crew machine-gunned every still surfaced survivors from Nancy Moller and left after two hours. The only POW remained afterwards in starvation diet for three months, then jailed in Singapore, but survived the war to tell the story. Still 32 men survived the sinking and massacre, rescued by HMS Emerald on 22 March, landed at Port Louis (Mauritius) on 26 March 1944.

On 12 August, I-165 sailed to Surabaya for a resupply mission to Korim Bay, arrived on the 18th but failed to see any of the troops and had to retired and dive under attack by three subchasers. Charges exploded close and created a major leak in her engine room. 10 hours after she surfaced and sailed Ambon forrepairs (23 August) and was forced to retire to Sasebo for repair and overdue overhaul. Later LtCdr Yasushi took command. She ended in SubDiv 19 as TS, but in 1945, I-165 was converted as a Kaiten carrier, then equipped with a Type 3 Mark 1 Model 3 “13-Go” air-search radar, entering the 6th Fleet, SubDiv 34. While en route to Saipan in the Mariannas she was spotted and sunk by a patrol bomber (Lockheed Hudson) of Sqn 142 (VPB-142) on 27 June 1945.

I-66/166 (19)

I-66 was commissioned at Sasebo on 10 November 1932. Upon commissioning, she was assigned to SubDiv 30, Sasebo Naval District, trained, but was decommissioned on 1 November 1934, placed in reserve. Recommissioned in December 1936, she was again active for a year and decommissioning on 1 December 1937, reserve, then recommissioned around September 1939. On 11 October 1940, she took part in the Imperial Naval Review in Tokyo Bay. On 21 October 1941, she collided with I-7 in Saeki Bay as part of naval maneuvers but damage was light. With I-65 made in SubDiv 30, SubRon 5 she left Sasebo on 26 November for Palau and the subs of SubDiv 29 led by the light cruiser Yura. They learned they were reassigned to the Southern Force on 28 November, then sent to Samah, Hainan Island, China. I-66 and I-65 arrived on 2 December. On 5 December she left Samah for her initial war patrol, taking part in the invasion of Malaya in the South China Sea, off Trengganu, Malaya, with I-57, I-58, I-62, and I-64. On 15 December she was detached for a reconnaissance off Kuching for the invasion of Sarawak, North Borneo on 16 December. She was warned of Allied submarines from Kuching.

While loading her batteries 60 nm (110 km; 69 mi) northwest of Kuching on 24 December she spotted HNLMS K XVI, which just sank the destroyer IJN Sagiri approaching while surfaced on her starboard bow from 5,500 yards (5,030 m). Her skipper ordered a crah dive, she turned, and fired a single torpedo which struck K XVI. The latter broke in two and sank with all hands. Sinking another sub always has been seen as the supreme “hunting achievement” for a submarine commander. On 4 October 2011, the Dutch wreck was rediscovered by Australian divers under 50 m. For I-66 this was a unique exploit, before I-176 sank USS Corvina.
She entered Patrol Unit “B” on 25 December and ended her patril at Cam Ranh Bay, Indochina on 27 December.

Still in Patrol Group “B” I-66 made a second sortie against Allied shipping, this time in the Indian Ocean with a new assigned base, Penang in Malaya. On 5 January 1942 she left Cam Ranh Bay for an area south of Lombok Strait (Andaman Sea) and to roam the Bay of Bengal. While underway in the Java Sea 10 nm (19 km; 12 mi) southwest of Lombok Strait on 11 January she spotted and torpedoed the 6,211 GRT USAT Liberty en route from Tanjung Priok (Dutch East Indie) with rubber and explosives. She survived, badly damaged, and called for help. USS Paul Jones and HNLMS Van Ghent arrived to tow her to Singaraja, Bali, but she had to be beached on northeast coast at Tulamben. She was later wrecked by the volcano Mount Agung, pushed into the ocean under 3-28m, now a favorite among divers.
On 21 January 1942, I-66 torpedoed the 3,193 GRT merchant “Nord” from Calcutta to Rangoon loaded with 2,500 tons of coal. This happened in the Preparis North Channel, Andaman Sea. All survived. On 22 January she torpedoed the British 2,358-ton GRT steamer Chak Sang from Madras to Rangoon empty (on ballasts) in the Bay of Bengal off Bassein, Burma. I-66 surfaced and finished her off by gunfire (5 killed). I-66 was back to Penang on 29 January. For her 3rd war patrol she became flagship of SubDiv 30.

On 9 February she sailed to the Indian Ocean off Ceylon and on the 14th while east of Trincomalee, she torpedoed the British 2,076 GRT “Kamuning” loaded with rice from Rangoon to Colombo. Again, she surfaced and finished her off with her deck gun (6 killed). Remaining afloat, she was later under tow to Trincomalee and sank later. I-66 was back to Penang on 2 March. On 15 March she headed for an overhaul at Sasebo, where she arrived on 28 March. She departed Sasebo on 15 May for Kwajalein, in advance of Operation MI against Midway Atoll. Renumbered I-166 on 20 May and back to Kwajalein on 24 May. 2 Days later she took part in a 4th patrol with SubRon 5 in the Advance Expeditionary Force, patrol line with I-156, I-157, I-158, I-159, I-162, and I-165. After the defeat they were recalled by Vice Admiral Teruhisa Komatsu westward. Yamamoto then ordered them to take a line forward of the retreating Japanese so they moved north-northwest at 3 knots by day, 14 knots by night. She was back to Sasebo on 26 June.

This summer saw a major overhaul after which she was reassigned to the Southwest Area Fleet, leaving on 22 July 1942 for Penang and a 5th patrol on 11 August in the Indian Ocean. She claimed sinking two Allied merchant on 16-17 August and was back on the 31st. On 18 September she started a 6th patrol in the Indian Ocean and made an attack on 29 September but missed. On 1 October 1942, she landed three Indian National Army agents on Ceylon (same mission as I-65). Later she atacked the Panamanian 1,201 GRT AMC “Camila” with gunfire, srtting her on fire, later beached and a total loss. She was back on 11 October.

For her 7th patrol she left on 5 November still in the Indian Ocean and preyed on Allied merchant ship in the Arabian Sea on 13 November (missed). On the 23th off Cape Comorin, she torpedoed the 5,332 GRT AMc Cranfield, from Calcutta to Suez (9 killed) and was back to Penang on 28 November For her 8th patrol she was assigned to the northwest coast of Australia, then ordered to shell Cocos Island on 25 December. She reited to Surabaya on 27 December. She headed for Sasebo, and a refit starting on 19 January in drydock, until July 1943 sailing to Surabaya for a 9th and 10th patrols for an area between Fremantle and Lombok Strait. No kills. She was back to Balikpapan on 10 September and a day latere departed for Singapore, arrived on 13 September to be reassigned to the Southwest Area Fleet, and returned to Penang on 25 September. On 9 October she refuelled at Sabang and sailed to the Indian Ocean for her 10th patrol, by late October attacked an Allied merchant ship off Colombo but missed. She was back on 13 November. Her 11th patrol started on 7 December but on the 24th she was divrted to take part in Operation YO (landing 6 Indian National Army agent at Kirindan Ceylon). British counterintelligence however did its job and they were all captured soon after coming ashore. I-166 then patrolled the Eight Degree Channel and was back to Penang on 9 January 1944.

She left on 7 February for her 12th patrol in the Bay of Bengal. On 19 February she missed the 6,943 GRT armed tanker British Fusilier, and returned to Penang on 13 March.
On 25 March SubDiv was reassigned to SubRon 8 and on 27 April she was called for the supply mission Operation RI, back to Penang on 1 June. On 16 July she was ordeed to meet Vice Admiral Takeo Kurita′s 1st Diversion Attack Force at Lingga Roads for the Philippnines great battle (Leyte) as antisubmarine warfare target for exercises. She never arrived.

On 17 July indeed, the T-class large submarine HMS Telemachus was patrolling at periscope depth in the strait of Malacca, some 7 nm (13 km; 8.1 mi) southeast the Fathom Bank in poor visibility. At 07:08 she spotted I-166 surfaceed from 4 nautical miles (7.4 km; 4.6 mi) at an estimated 18 knots, then established sound contact and conformed the distance. She placed hrself at the right angle and fired at 07:20, a full spread of six torpedoes from just 1,500 yards (1,370 m), but broached briefly due to the heavier torpedo used and liberation of all six in short order. After 92 seconds, one hit I-166 on her stern. Whatever it hit, there was a violent explosion and she sank under 130 feet (40 m). Only 10 men survived, blown overboard and captured. Overdue, HQ Penang sent the minelayer Wa-4 and two TBs plus a Mitsubishi Ki-21 (“Sally”) to find I-66. They eventually spotted and attacked Telemachus but she escaped without damage. I-166 was stricken on 10 September 1944.

I-67/167 (1934)

I67 I67 was commissioned on 8 August 1932 and attached to the Kure Naval District, assigned to Submarine Division 30. When the submarine I-66 was commissioned on 10 November 1932, she joined her in the division, reassigned to the Sasebo Defense Division and District. All three in class were together from December 1932, under SubRon 1 for the 1st Fleet, Combined Fleet. They went to SubRon 2 on 15 November 1933. On 27 September 1934, she departed Ryojun for a training cruise in the Qingdao area and back to Sasebo on 5 October 1934. SubDiv 30 returned under the Sasebo Guard Squadron and District on 15 November and returned to SubRon 2 on 15 November 1935. On 13 April 1936, she left Fukuoka for a training cruise again to Qingdao and bacl to Sasebo on 22 April. Then she headed for Mako (Pescadores Islands) by August for another training cruise off Amoy and back on 6 September. She was then decommissioned in reserve at Sasebo from December 1937, then 3rd Reserve from next December 1938 but recommissioned on 15 November 1939, under SubRon 4, 1st Fleet.

In August 1940, I-67 sailed for the Bonin Islands and a Combined Fleet exercise with her division and exercise judge on board plus her full crew of 89. While off the southern coast of Minamitorishima on 29 August a seaplane from Mizuho was sent to “attack her” so she practiced a crash dive to avoid it, bu as the pilot noted, she never resurfaced. In the evening she was reported overdue to report. As time goes by it was assumed she lost her radio. But a day later a search was launched in her last area. It happened she had sank with 91 men on board. No debris was seen, neither an oil slick. She vanished underwater and was declared at last presumed sank with all hands on 25 September 1940 by the IJN staff, stricken on 1 November 1940. The loss cause remains unknown. Mizuho′s seaplane pilot was interrogated and claimed he believed she “submerged with a rear hatch still open”. Investigators concluded this in their report, but before her wreck is found again and investigated, there is no way to be certain.