SENSUIKAN!

© 2001-2017 Bob Hackett & Sander Kingsepp

16 November 1937:
Laid down at Mitsubishi's Kobe Yard as C-1 class submarine No. 46.

25 January 1939
Launched as I-20.

25 March 1940
Cdr (Rear Admiral, posthumously) Yamada Takashi (49)(former CO of RO-60) is appointed the Chief Equipping Officer (CEO).

26 September 1940:
Kobe. I-20 is completed, commissioned in the IJN and attached to Yokosuka Naval District. Cdr Yamada Takashi is the Commanding Officer.

Fall 1940:
Participates in the tests of the German Periphon A passive sonar, manufactured by the Atlas-Werke Company in Bremen.

31 January 1941:
I-20 is assigned to SubRon 1's SubDiv 2, Sixth Fleet (Submarines).

15 November 1941:
I-20 is in Vice Admiral Shimizu Mitsumi's (former CO of ISE) Sixth Fleet, in Rear Admiral Sato Tsutomu's SubRon 1, in Captain Imaizumi Yoshijiro's SubDiv 2 with I-18 and I-19.

17 November 1941: Operation "Z" - The Hawaiian Operation:
Kure Naval Club. The officers of Captain (later Rear Admiral) Sasaki Hankyu's Special Attack Unit are briefed on the Hawaii Operation. For Operation "Z", I-20 is assigned to the Special Attack Unit with I-16, -18, -24 and the flagship, I-22.

18 November 1941:
The Special Attack Unit departs Kure for the Kamegakubi Naval Proving Ground. At Kamegakubi each of submarines embarks a top secret 46-ton two-man Type "A" midget submarine.

19 November 1941:
At 0215, all five of the Special Attack Unit's submarines depart Kamegakubi for the Hawaiian Islands. They use a direct route, passing S of Midway.

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). [1]

7 December 1941: The Attack on Pearl Harbor:
5.3 miles from the harbor entrance. At 0257, I-20 launches her midget submarine under Ens Hiroo Akira (68) with PO2C Katayama Yoshio. [2] Each of the other of the Special Attack Unit's "mother" submarines also launches their midget.

At 0408, Lt. W. W. Outerbridge's old USS WARD (DD-139) begins a search for a suspected submarine reported by the minesweeper CONDOR (AMC-14), but finds nothing. At 0630, as Training Squadron 8's flagship 8 USS ANTARES (AKS-3) approaches Pearl's outer gate with a target raft in tow, the WARD's lookouts spot a small conning tower. A patrolling PBY "Catalina" flying-boat 14-P-1, flown by Ens. William P. Tanner of Patrol Squadron VP-14, drops smoke markers on the contact.

At 0645, the WARD opens fire at 100 yards. Her first round - the first shot fired in WWII by American Forces - misses. She closes to point blank range (50 yds) and fires a 4-inch shell hitting the midget's conning tower. WARD overruns her target and the midget wallows in her wake. Outerbridge orders four depth charges dropped and signals his 14th Naval District Headquarters: "WE HAVE ATTACKED FIRED UPON AND DROPPED DEPTH CHARGES UPON SUBMARINE OPERATING IN DEFENSIVE SEA AREA."

The PBY drops more depth bombs. Hiroo and Katayama's midget is sunk. All five of the Special Attack Unit's midgets fail to return to their "mother" submarines.

9 December 1941:
Early in the morning, I-20, I-18 and I-24 depart the recovery area S of Lanai.

12 December 1941:
I-20 departs the Hawaii area for Kwajalein.

20 December 1941:
Arrives at Kwajalein with I-16.

4 January 1942:
Departs Kwajalein on her first patrol in the Samoa-Fiji area.

11 January 1942:
Pago-Pago harbor, Tutuila Island, American Samoa. Before dawn, I-20 surfaces 15,000 yds off Tutuila's north coast and fires 12 shells from her 14-cm deck gun, targeting the local naval station. Most shells miss; one Marine officer and a member of the Samoan Marine Reserve Battalion are wounded by shrapnel.

16 January 1942:
Suva, Fiji. Cdr Yamada fires two torpedoes at the 10,852-ton HMNZS MONOWAI (ex-RAZMAK), a former trans-Tasman liner commissioned as an armed merchant cruiser, which has just departed Suva harbor. At 1603 both torpedoes explode prematurely. Five minutes later, when I-20 surfaces 7,400 yds away to finish off the apparent merchant ship, she is met with a hail of gunfire from the MONOWAI's port side six-inch guns. I-20 continues to fire, claiming a hit on MONOWAI's bridge. After being straddled, Cdr Yamada crash-dives at 1614. MONOWAI steams away at high speed, sending an SSS (submarine alert) signal. Neither side is damaged.

24 January 1942:
Returns to Kwajalein, then departs for Yokosuka.

1 February 1942:
Arrives at Yokosuka.

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

8 April 1942:
The Japanese formally agree to dispatch submarines to the East Coast of Africa.

16 April 1942:
I-20 is in Captain (later Rear Admiral) Ishizaki Noboru's (former CO of HYUGA) SubRon 8, in the KO ("A") detachment with the I-10, I-16, I-18, I-30 and their support ships, the auxiliary cruisers/supply ships AIKOKU MARU and the HOKOKU MARU.

Hashirajima, Hiroshima Bay. Vice Admiral Komatsu, Captain Ishizaki their staffs and midget submarine crews pay a courtesy call on the CinC, Combined Fleet, Admiral Yamamoto aboard his flagship, the new battleship YAMATO. At 1100, the A detachment departs for Penang, Occupied British Malaya.

22 April 1942:
I-30 is to reconnoiter selected points on the East African coast for possible attack and departs Penang in advance of the "A" detachment.

27 April 1942:
I-20 arrives at Penang with the "A" detachment. I-16, I-18 and I-20 are joined by the seaplane tender NISSHIN that had been converted to carry Type A midget submarines. Each of the three "mother" submarines is loaded with a midget.

30 April 1942:
I-20 departs with the "A" detachment (less I-30) and sorties westward in the Indian Ocean under the command of Captain Ishizaki in the aircraft-carrying flagship I-10 that is to reconnoiter selected points on the East African coast for possible attack. I-30 is assigned a similar reconnaissance mission and departs in advance.

5, 10 and 15 May 1942:
The "A" detachment refuels at sea from AIKOKU MARU and the HOKOKU MARU.

17 May 1942:
While proceeding surfaced, I-20's engine room is flooded in heavy seas through the main induction valve. Just after all damage is repaired, the same compartment is flooded the second time.

20 May 1942:
I-10 catapults her Yokosuka E14Y1 "Glen" floatplane to reconnoiter Durban, South Africa.

24 May 1942:
Captain Imaizumi reports to Captain Ishizaki about the heavy traffic encountered en route to the target area.

29 May 1942:
At night, the I-10's floatplane reconnoiters the harbor at Diego Suarez, Madagascar. The plane sights HMS RAMILLIES, an old 29,150-ton ROYAL SOVEREIGN-class battleship, at anchor in the bay. Also in the harbor are the destroyers HMS DUNCAN and ACTIVE, corvettes HMS GENISTA and THYME, troopship HMS KARANJA, hospital ship ATLANTIS, tanker BRITISH LOYALTY, merchant LLANDAFF CASTLE and an ammunition ship.

Captain Ishizaki orders a midget submarine attack for the next night.

30 May 1942: The Attack on Diego Suarez:
10 miles from Diego Suarez. I-20 launches her midget submarine under Lt Akieda Saburo (66) with PO1C Takemoto Masami to attack RAMILLIES. I-16 also launches her midget, but the I-18's midget suffers engine failure and cannot be launched. At 2025, Lt Akieda's midget torpedoes and heavily damages the RAMILLIES. At 2120, while British corvettes drop depth charges, Akeida torpedoes and sinks the 6,993-ton BRITISH LOYALTY in shallow water. (She is later refloated and sunk off Addu Atoll). Ten days later, the RAMILLIES makes for Durban, Union of South Africa.

Lt Akieda and PO1C Takemoto's craft is beached. Aided by natives, both sailors reach the shore and head for the recovery area.

After the attacks, the I-10's aircraft reconnoiters the harbor twice to assess the results. The missing RAMILLIES is erroneously considered sunk by the IJN.

1 June 1942:
Around 1100, both Japanese are spotted off Anijabe village. The natives report their sighting to the British.

2 June 1942:
Amponkarana Bay (12-00S, 49-12E). Lt Akieda and PO1C Takemoto are intercepted by Royal Marines' Commando No. 5. During the ensuing gunfight both Japanese and one Marine are killed.

3 June 1942:
After the other "mother" submarines depart the recovery area, I-20 surfaces and unsuccessfully tries to contact the midgets by firing flares and sending radio signals.

5 June 1942: Commerce Raiding in the Indian Ocean:
I-20 torpedoes and sinks the 5,086-ton Panamanian-flagged armed merchant JOHNSTOWN (ex-NIEL MAERSK) at 13-12S, 42-06E.

8 June 1942:
Indian Ocean. I-20 torpedoes and sinks the 5,209-ton Greek merchant CHRISTOS MARKETTOS (ex-QUEEN MAUD) at 05-05S, 40-53E.

11 June 1942:
Indian Ocean. I-20 torpedoes and sinks the 7,926-ton British armed merchant MAHRONDA at 14-37S, 40-58E.

12 June 1942:
I-20 shells and sinks the 2,052-ton Panamanian-flagged merchant HELLENIC TRADER at 14-40S, 40-53E.

Later that day, I-20 torpedoes and sinks the 5,063-ton British merchant CLIFTON HALL at 16-25S, 40-10E.

19 June 1942:
Refuels from AIKOKU MARU.

29 June 1942:
Indian Ocean. I-20 torpedoes the 5,063-ton Norwegian armed merchant GOVIKEN (ex-GOLDEN GATE), en route from Aden to Lourenço Marques, Mozambique. She sinks within 20 minutes at 13-25S, 41-53E.

30 June 1942:
Indian Ocean. I-20 attacks the 5,311-ton British steam tanker STEAUA ROMANA (ex-OLEX) at 09S, 42E. First she fires 15 shells from her deck gun, achieving one hit. When STEAUA ROMANA returns fire, Yamada dives and fires a torpedo, that explodes prematurely. The tanker drops a smoke float and tries to open the range but is sunk by a second torpedo.

Later that day, using Allied radio communication intercepts, LtCdr Yamada ascertains his victim's name.

5 July 1942:
In order to discover the cause of his frequent torpedo prematures, Cdr Yamada orders one Type 95 to be dismantled aboard.

21 July 1942:
I-20 extends her patrol to the Gulf of Aden, then returns to Penang.

5 August 1942:
Arrives at Penang.

7 August 1942: American Operation "Watchtower" - The Invasion of Guadalcanal, British Solomon Islands:
Rear Admiral (later Admiral) Richmond K. Turner's Amphibious Task Force 62, covered by Vice Admiral (later Admiral) Frank J. Fletcher's Task Force 61 and Rear Admiral (later Admiral) John S. McCain's Task Force 63's land-based aircraft, lands Maj Gen (later Gen/MOH/Commandant) Alexander A. Vandegrift's 1st Marine Division on Florida, Tulagi, Gavutu, Tanambogo and Guadalcanal opening the campaign to retake the island.

23 August 1942:
Returns to Yokosuka for repairs and overhaul.

15 September 1942:
Cdr (later Captain) Yoshimura Iwao (51)(former CO of I-27) is appointed the CO.

7 October 1942:
A midget submarine base is established at Marovovo.

24 October 1942:
I-20 departs Yokosuka to operate in the Solomons area.

2 November 1942:
I-20, I-16 and I-24 form an attack group under Captain Ota Nobunosuke. At the Shortland Islands anchorage, each of the three I-boats' decks is loaded with a midget submarine brought from the Empire aboard the tender CHIYODA. They are ordered to Indispensable Stait off Guadalcanal.

5 November 1942:
I-20 embarks her new midget Ha-11 under Lt(j.g.) Kunihiro Nobuharu (68) and PO1C Inoue Goro. Departs that evening. [3]

7 November 1942:
4 miles N of Cape Esperance, Guadalcanal. At 0520 I-20 launches her midget, the HA-11. Lt(j.g) Kunihiro fires one Type 97 torpedo and damages the anchored 2,227-ton miscellaneous auxiliary MAJABA (AG-43). The MAJABA is beached, but later salvaged. The destroyers LANDSDOWNE (DD-486) and the LARDNER (DD-487) counterattack, but fail to damage the craft. Ha-11 is scuttled and her crew escapes ashore. I-20 returns to Truk.

13 November 1942:
At Truk, I-20 embarks her fourth midget HA-37 under Lt(j.g.) Miyoshi Yoshiaki (69) and PO1C Umeda Kiyoshi. Departs Truk for the Lunga Point area.

16 November 1942:
Truk. Vice Admiral Komatsu convenes a meeting of his submarine captains. He announces that the submarine force has been ordered by Admiral Yamamoto, CINC, Combined Fleet to organize a supply system for the IJA garrison on Guadalcanal.

18 November 1942:
I-20 arrives at her assigned launch area.

19 November 1942:
6 miles off Cape Esperance. At 0300, HA-37 is launched from I-20. Two minutes later a serious oil leak develops from her steering system. Lt(j.g.) Miyoshi decides to continue his approach on the surface, but sights no targets. At 0955, HA-37 is scuttled off Cape Esperance. Her crew escapes ashore.

26 November 1942:
At Truk, I-20 embarks her fifth midget, the HA-8 under Lt (j.g.) Tanaka Chiaki (69) and CPO Mitani Mamoru. Departs Truk for the Lunga Point area.

1 December 1942:
I-20 arrives at her assigned launch area.

2 December 1942:
19 nms off Savo Island. HA-8 is launched from I-20.

3 December 1942:
Lt(j.g.) Tanaka sights several targets, including transports and destroyers. After being beached for a short while, he fires both of his torpedoes at a transport; one explosion is heard. HA-8 is chased by a destroyer, but receives no damage. After the surfaced craft is swamped off Cape Esperance, the crew decides to scuttle. Both Tanaka and Mitani reach the shore. [4]

18 December 1942:
LtCdr (Captain, posthumously) Kudo Kaneo (56)(former CO of I-155) is appointed the CO.

31 December 1942:
Arrives at Cape Esperance on her first supply run to Guadalcanal, delivering 25-tons of cargo in rubber containers.

2 January 1943:
Departs Truk for Shortland.

January 1943:
Arrives at Shortland, then departs.

7 January 1943:
At night, arrives at Cape Esperance on her second supply run to Guadalcanal, delivering 18-tons of cargo in rubber containers.

20 January 1943:
Departs Shortland for Cape Esperance, towing an 18-ton "Unkato" supply container (the first IJN "Unkato" mission).

22 January 1943:
At night, arrives at Cape Esperance on her third supply run to Guadalcanal. Delivers her cargo, then departs.

18 March 1943:
Departs Truk.

21 March 1943:
Delivers 30 tons of food and ammunition to Lae.

27 March 1943:
Delivers food and ammunition on her second supply run to Lae, then departs.

2 April 1943:
S of New Britain. During her third supply run to Lae, I-20 receives slight damage in an underwater collision with I-16.

3 April 1943:
Delivers 37-tons of cargo to Lae. Evacuates 39 men, including LtGen Adachi Hatazo and his staff.

9 April 1943:
Delivers 30 tons of cargo on her fourth supply run to Lae. Evacuates 42 soldiers.

11 April 1943:
Solomon Sea, 90 miles E of Gasmata, New Britain. At 0513 (local), the surfaced I-20 sights another surfaced submarine and commences an approach. In the predawn darkness the contact is lost and LtCdr Kudo somewhat reluctantly abandons the chase.

I-20's "adversary", LtCdr Sekido Yoshimitsu's I-5, en route to Lae on another supply mission, had spotted her just three minutes earlier, correctly identified as a Japanese submarine and moved out of the way to avoid a potential "friendly fire" situation.

13 April 1943:
I-20, -5, -6 and I-16 are temporarily attached to the Eighth Fleet HQ.

15 April 1943:
Delivers 37-tons of cargo on her fifth supply run to Lae. Off Lae, the submarine is illuminated by flares dropped from an enemy bomber. Evacuates 40 soldiers.

20 April 1943:
Delivers food and ammunition to Kolombangara.

2 May 1943:
Delivers 39 tons of cargo on her sixth supply run to Lae, evacuates 31 soldiers.

8 May 1943:
Delivers 39 tons of cargo on her seventh supply run to Lae.

15 May 1943:
I-20, I-5 and I-6 are re-attached to the Eighth Fleet HQ.

20 May 1943:
Arrives at Yokosuka for an overhaul.

2 June 1943:
LtCdr (Cdr, posthumously) Otsuka Susumu (56)(former CO of I-158) is appointed the CO.

4 August 1943:
Reassigned to SubRon 1. Departs Yokosuka.

10 August 1943:
Arrives at Truk.

19 August 1943:
Departs Truk on her second war patrol in the New Hebrides area.

30 August 1943:
LtCdr Otsuka reports sighting an enemy force off Espiritu Santo that includes a carrier and two battleships.

31 August 1943:
10 miles N of Bougainville Strait. I-20 reports torpedoing and damaging the 10,872-ton American tanker W. S. RHEEM at 15-51S, 167-02E. This is the last signal received from I-20.

3 September 1943:
LtCdr T. C. Phifer's USS ELLET (DD-398) is ordered out of Espiritu Santo on an ASW sweep for a reported submarine. At 1935, ELLET picks up a contact on her SG radar at 13,000 yards. Phifer closes to about 5,000 yards and challenges the unseen contact with his blinker gun. There is no reply.

ELLET illuminates the sea with starshells. The target disappears at 3,400 yards. ELLET's sonar picks up a contact at 3,000 yards. At 2012, LtCdr Phifer makes a depth charge attack, then drops more patterns until 2038. Contact is broken off at 2059. At daybreak a large oil slick and debris are spotted at 13-10S, 165-28E. The identity of the submarine that the ELLET sank remains unknown. [5]

18 November 1943:
Presumed lost with all 101 hands off Espiritu Santo.

1 December 1943:
Removed from the Navy List.

3 July 2001:
Amponkarana Bay, Japan. The JMSDF erect a monument for the four midget crews. Present are the crew of the training vessel KASHIMA and the ceremony is led by Rear Admiral Yasui Nobuharu.

28 August 2002
3-4 miles S of Pearl. The University of Hawaii Undersea Research Lab (HURL) deep-diving submersibles Pisces IV and V find a midget in excellent condition resting almost upright on the bottom in 1,200 feet of water. There is speculation that it may be Hiroo and Katayama's submarine.

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Authors' Notes:
[1] Mt. Niitaka, located in Formosa (now Taiwan), was then the highest point in the Japanese Empire.

[2] Japanese submarine historian Katsume Junya has identified that craft as No. 17.

[3] The IJN did not use the HA designations in case of the submarine-launched craft (or "midget submarines") during the Pacific War. They are used here for convenience only.

[4] On 7 May 43, the submarine rescue vessel USS ORTOLAN (ASR-5) (former AM-45) salvaged a Japanese midget submarine off the N coast of Guadalcanal, tows her to Kukum Bay, Guadalcanal in May and then in June '43 delivered her to Noumea, New Caledonia. Some sources identify the midget as HA-8, others as HA-10 and still others as HA-30. Whichever she truly is, the "Guadalcanal midget" is displayed at the Nautilus Memorial Submarine Force Library and Museum in Groton, CT, one of four such Type A midgets on display around the world.

[5] I-20 and I-182 were operating in the New Hebrides at this time and neither submarine returned from their mission. Japanese author Kimata Jiro credits USS ELLET (DD-398) with the sinking of I-20, but it is possible she was sunk by the WADSWORTH (DD-516) on 1 September 1943.

Special thanks for help in preparing this TROM go to Dr. Higuchi Tatsuhiro of Japan.

– Bob Hackett and Sander Kingsepp.

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