(Type B1 submarine - colorized photo by Irootoko Jr)
IJN Submarine I-21:
Tabular Record of
© 2001-2012 Bob Hackett & Sander Kingsepp
24 February 1940:
7 January 1939:
Laid down at Kawasaki Kobe Yard as Submarine No. 40.
Launched as I-21.
31 January 1941:
Cdr Irie Tatsushi (51)(former CO of I-53) is appointed Chief Equipping Officer.
15 July 1941:
Completed and attached to Yokosuka Naval District. Cdr Irie is the Commanding Officer. Assigned to the Sixth Fleet, SubDiv 3 in SubRon 1 with I-22.
31 October 1941:
Cdr Matsumura Kanji (former CO of RO-65, -66, -61) is assigned as the Commanding Officer.
10 November 1941: Operation "Z":
At Saeki Bay in Vice Admiral Shimizu Mitsumi's (former CO of ISE) Advance Expeditionary Force (Sixth Fleet). Shimizu convenes a meeting of all his commanders aboard his flagship, light cruiser KATORI. Cdr Matsumura and the other commanders are briefed on the planned attack on Pearl Harbor.
19 November 1941:
22 November 1941:
Arrives at Hitokappu Bay, Etorofu.
25 November 1941:
I-21's crewmembers visit carrier SORYU to use her bathing accommodations.
26 November 1941:
Departs Hitokappu for the Hawaiian Islands on her first "war" patrol with I-19 and I-23 to act as lookouts ahead of the Carrier Striking Force.
27 November 1941:
En route, I-19, I-21 and I-23 refuel from a fleet oiler.
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:
I-21 is in Rear Admiral Sato Tsutomu's SubRon 1 in Captain (later Rear Admiral) Sasaki Hankyu's SubDiv 3 with I-22 and I-23. I-21 is assigned to patrol north of Oahu, Hawaii.
9 December 1941:
I-6 reports sighting a LEXINGTON-class aircraft carrier and two cruisers heading NE. Vice Admiral Shimizu at Kwajalein orders all of SubRon 1 boats, except the Special Attack Force, to pursue and sink the carrier.
I-21, I-9, I-15, I-17, I-19, I-23 and I-25 all surface and set off at flank speed after the carrier.
11 December 1941:
I-21's chase to intercept USS ENTERPRISE (CV-6) is marred by diesel breakdowns and electrical troubles. She is also spotted by several Douglas "Dauntless" SBD dive-bombers and forced to dive each time.
13 December 1941:
Cdr Matsumura decides to battle it out with the chasing aircraft. Around 1300, I-21 is attacked by a single plane from the port quarter. After the first run is foiled, the aircraft turns back, dives and drops one bomb which falls near the port side but fails to explode.
14 December 1941:
After an unsuccessful pursuit of the carrier, I-21 and the other submarines are ordered eastwards to the West Coast of the United States to attack American shipping. I-21 is assigned to patrol off Point Arguello, California.
23 December 1941:
I-21 sights Union Oil Company's tanker MONTEBELLO that had departed Port San Luis, California, en route to Vancouver, British Columbia. Cdr Matsumura fires two torpedoes from 2,190 yards (2,000 meters). One of them is a dud, but the other explodes in her No. 2 hold. The 38-man crew abandons the tanker in four lifeboats. Matsumura fires several shells from his deck gun to speed the sinking. In about an hour, MONTEBELLO goes under four miles S of Piedras Blancas light at 35-35N, 121-16W. 
Later in the day, I-21 shells and damages American tanker IDAHO near the same location.
24 December 1941:
About 0800 (JST), I-21 is depth-charged. The attacker is identified as a Consolidated PBY "Catalina" flying boat.
While running at periscope depth, I-21's 'scope is spotted by what Matsumura identifies as a small "Coast Guard patrol boat". In a well-executed attack with only two depth-charges the patrol boat knocks out I-21's vertical rudder and all her lights. Cdr Matsumura gives the order to surface and battle it out, but at the last minute the emergency lighting is restored and the engineers manage to repair the steering.
11 January 1942:
Arrives at Kwajalein. Cdr Matsumura is credited with the sinking of two enemy oilers. That same day, LtCdr J. H. Willingham's USS TAUTOG (SS-191) spots three IJN subs going into Kwajalein, one of which may have been I-21.
23 January 1942:
Departs Kwajalein for Yokosuka.
1 February 1942:
Arrives at Yokosuka.
10 March 1942:
SubDiv 3 is reassigned to SubRon 8 under Captain (later Rear Admiral) Ishizaki Noboru (former CO of HYUGA).
10 April 1942: Operation "C" - The Raids in the Indian Ocean:
Admiral (Fleet Admiral, posthumously) Yamamoto Isoroku (former CO of AKAGI), CINC, Combined Fleet, orders all submarine units to reconnoiter the enemy's fleet bases in the Indian Ocean and the South Pacific, destroy the enemy's maritime commerce and support the Port Moresby (MO) Operation.
15 April 1942:
I-21 is in Captain (later Rear Admiral) Sasaki Hankyu's Eastern Advanced Detachment with I-22, I-24, I-27 I-28 and I-29. All 11 submarines of SubRon 8 complete extensive exercises in the Inland Sea.
15 April 1942:
SubRon 8 arrives at Hashirajima. Admiral Yamamoto addresses the captains of the Eastern detachment's submarines.
16 April 1942:
All six of the Eastern detachment's submarines depart Kure.
18 April 1942: The First Bombing of Japan:
Vice Admiral (later Fleet Admiral) William F. ("Bull") Halsey's Task Force 16
USS HORNET (CV-8), cruisers, destroyers and an oiler accompanied by USS ENTERPRISE (CV-6), cruisers, destroyers and another oiler approach to within 668 nautical miles of Japan. Led by LtCol (later Gen/Medal of Honor) James H. Doolittle, 16 Army North American B-25 "Mitchell" twin-engine bombers of the 17th Bomb Group takeoff from Captain (later Admiral) Marc A. Mitscher's carrier HORNET and strike targets in Tokyo, Yokohama, Osaka, Nagoya and Kobe.
E of the Bonin Islands. I-21 is enroute from Japan to Truk. Headquarters, Combined Fleet orders I-21 and the other submarines to intercept Task Force 16, but they are unable to make contact.
25 April 1942:
Rabaul. Refueled by KAGU MARU.
27 April 1942:
Departs Truk with I-27 and heads for Noumea, with ComSubDiv 3 Captain Sasaki Hankyu embarked, carrying a Yokosuka E14Y1 "Glen" for her second war patrol. The pilot is CPO Ito Susumu.
2 May 1942:
Coral Sea. Enroute to Noumea, surfaced I-21 is spotted by a SBD "Dauntless" scout plane of VS-5 from USS YORKTOWN (CV-5). In order to maintain radio silence, the pilot drops a message tube with his sighting report when returning to the carrier 25 miles away. Three Douglas TBD "Devastators" of VT-5, each carrying two Mark 17 depth charges are launched.
I-21's lookouts spot the approaching torpedo bombers and she crash-dives. The pilots report the submarine as "probably damaged or sunk". One hour after the attack when I-21 surfaces, a number of bomb fragments are found on her afterdeck. Cdr Matsumura sends a report but is unable to specify whether or not his attackers were carrier-based. Task Force 17's approach to the Solomons thus remains undetected.
4 May 1942: Operation "MO" - The Invasions of Tulagi and Port Moresby:
Rear Admiral Kajioka Sadamichi's Port Moresby Attack Force departs Rabaul towards the Jomard Pass in the Louisiade Archipelago with DesRon 6's light cruiser YUBARI, four destroyers and a patrol boat escorting Rear Admiral (later Vice Admiral) Abe Koso's Transport Force of 12 transports and a minesweeper.
5 May 1942:
Off Nouméa, New Caledonia. I-21 sights American "Liberty" ship JOHN ADAMS at night. After a two-hour chase, Cdr Matsumura fires two Type 95 oxygen torpedoes that both hit ADAMS, carrying 2,000 tons of gasoline. She sinks at 23-11S, 165-08E. JOHN ADAMS is the first Liberty ship sunk in the Pacific.
7 May 1942:
About 0630, I-21 arrives at an area 20 miles W of Noumea. She picks up propeller noises with her sonar and starts an approach. Cdr Matsumura fires two Type 95 torpedoes, but both explode prematurely. I-21 surfaces and engages 4,641-ton Greek merchant CHLOE with her deck gun, firing 70 shells. After the merchant is sunk at 22-59S, 166-29E, Cdr Matsumura supplies the life boats with food and provides them with the bearing on Noumea.
8 May 1942:
Cdr Matsumura attacks a large merchant in the same area but fails to hit her with torpedoes. I-21 surfaces to engage the target with gunfire but is forced to submerge by a patrol plane that drops six depth charges.
SBD dive-bombers from YORKTOWN and LEXINGTON damage Vice Admiral (Admiral, posthumously) Takagi Takeo's (former CO of MUTSU) carrier SHOKAKU and force her retirement. ZUIKAKU's air group suffers heavy losses. Japanese carrier bombers and attack planes attack Task Force 17 and damage YORKTOWN and LEXINGTON. LEXINGTON is further damaged when gasoline vapors ignite and trigger massive explosions. LEXINGTON has to be abandoned and later is scuttled by destroyer PHELPS (DD-360), but the Battle of the Coral Sea halts the Japanese thrust toward Port Moresby and they are forced to cancel Operation MO.
14 May 1942:
The I-21 departs the Noumea area.
15 May 1942:
A Kawanishi H6K "Mavis" flying boat of the Yokohama NAG spots ENTERPRISE and HORNET off the Solomon Islands. Cdr Matsumura receives an order from Vice Admiral Komatsu on Kwajalein to reconnoiter the Suva Harbor, Fiji, where a new American naval base is suspected to be.
19 May 1942:
Early in the morning, Warrant Flying Officer Ito conducts a recce flight over Suva. He sights a Glasgow-class light cruiser and seven submarine chasers in the harbor and returns to the submarine one and a half hours later.
24 May 1942:
At dawn, I-21's "Glen" reconnoiters Auckland, New Zealand. As a result of a heavy squall, Ito fails to detect any vessels in the harbor. When flying over the Auckland airfield at 1,315 feet, landing lights are switched on for him by the New Zealanders.
29 May 1942:
35 miles NE of Sydney, Australia. CPO Ito is launched from I-21 to make a pre-midget submarine attack reconnaisance in his Glen. Ito is caught by three searchlights over Cockatoo Island, but manages to escape.
At 0420, a floatplane with its navigation lights on is sighted as it circles twice over the harbor near where USS CHICAGO (CA-29) is anchored. It is thought to be an American plane, but eventually RAAF fighters are sent up to intercept, but they are unsuccessful. While landing in heavy seas, Ito's plane capsizes and is later scuttled. Ito reports sighting a "battleship". He also spots converted hospital ship ORANJE. Captain Sasaki orders an attack on Sydney harbor by his midget submarines.
31 May 1942:
I-22, I-24 and I-27 launch their midget submarines. One becomes entangled near the entrance and is blown up to prevent capture. The other midgets penetrate the harbor and fire their torpedoes. They miss CHICAGO, but sink old accommodation ferry HMAS KUTTABUL and damage Dutch submarine K-IX beyond repair.
3 June 1943:
After lingering off Port Hacking to recover the midgets that fail to return, I-21 and the other submarines finally give up and switch to commerce warfare.
8 June 1942:
At 0215, after crossing the Stockton Bight, I-21 opens fire at the shipyard in Newcastle. Thirteen minutes later the shore battery at Fort Scratchley returns fire, but the submarine continues the shelling for three more minutes. In all, 26 HE and 8 star shells are fired by I-21 using a new type of flashless powder, but they cause minimal damage and no casualties. The fort fires four shells in return. Later that day, Cdr Matsumura spots a convoy heading for Melbourne but is unable to attack.
11 June 1942:
The I-21 is chased by a radar-equipped destroyer.
12 June 1942:
40 miles off Sydney. The Australian Government chartered Panamanian-flagged freighter GUATEMALA is in an eight-ship convoy from Newcastle to Whyalla with 4,200 tons of coke. At 0114, surfaced I-21 fires four torpedoes at two merchants in the convoy, but hits only GUATEMALA. She sinks about an hour later off Cape Three Points. Her crew is rescued by HMAS DOOMBA.
25 June 1942:
Arrives at Kwajalein.
12 July 1942:
Arrives at Yokosuka for repairs and an overhaul.
7 August 1942 - 9 February 1943: American Operation "Watchtower" - The Invasion of Guadalcanal, Solomons:
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/Commandant) Alexander A. Vandergrift's 1st Marine Division on Guadalcanal opening a seven-month campaign to take the island.
14 August 1942:
I-21 is in Vice Admiral, the Marquis, Komatsu Teruhisa's Sixth Fleet (Submarines) at Truk in Subron 1 with I-15, I-16, I-17, I-18, I-19, I-20, I-22, I-24, I-25 and I-26.
23 August 1942:
Departs Yokosuka for the eastern Solomons with ComSubDiv 3 Capt Sasaki aboard for her third war patrol. She is carrying a E14Y1 Type 0 "Glen" floatplane.
31 August 1942:
NW of Espiritu Santo, Solomon Islands. Around 0800, the sonarman of I-21 registers 37 depth charge explosions from the western direction. This is USS PHELPS (DD-360) and MACDONOUGH (DD-351), chasing I-26 which has just torpedoed USS SARATOGA (CV-3).
13 September 1942:
345 miles SSE of Guadalcanal. Early in the morning, a Kawanishi H8K "Emily" flying boat of the Yokohama NAG sights one carrier, two battleships and two destroyers steaming north. I-21, I-9, I-15, I-17, I-24, I-26, I-31 and I-33 are ordered to form a patrol line and intercept the enemy task force.
2 October 1942:
At dawn, CPO Ito conducts a recce flight over the airfield on Espiritu Santo, New Hebrides.
7 October 1942:
Off Truk. I-21 is running surfaced when she is attacked by LtCdr R. C. Lake's USS ALBACORE (SS-218). I-21's lookouts sight the ALBACORE's periscope at 4,380 yards (4,000 meters) and at the last moment, I-21 turns into ALBACORE and spoils Lake's shooting solution.
8 October 1942:
I-21 arrives at Truk.
26 October 1942: The Battle of Santa Cruz:
Rear Admiral (later Admiral) Thomas C. Kinkaid's Task Force 16 and Rear Admiral George D. Murray's Task Force 17 engage Vice Admiral Nagumo Chuichi's carrier force. ENTERPRISE (CV-6) is damaged by planes from carriers JUNYO and SHOKAKU. JUNYO's planes damage SOUTH DAKOTA (BB-57) and SAN JUAN (CL-54). Planes from JUNYO, SHOKAKU and ZUIKAKU damage HORNET (CV-8). USS PORTER (DD-356) is sunk. IJN destroyers scuttle HORNET much later that day. 
SBD dive-bombers of VS-10 from ENTERPRISE damage carrier ZUIHO. SBD's of VB-8 and VS-8 from the HORNET damage the carrier SHOKAKU and destroyer TERUTSUKI. Grumman TBF torpedo-bombers of VT-6 from the HORNET damage the cruiser CHIKUMA.
27 October 1942:
At 0638, 150 miles S of the Indispensable Reef (15-30S, 160-42E), I-21's lookouts sight a "Colorado-class battleship". Cdr Matsumura fires a spread of six torpedoes at 2-second intervals and one explosion is heard. One torpedo broaches as a result of the faulty steering and one explodes in new battleship USS WASHINGTON's (BB-56) wake. No damage is inflicted. I-21 is then depth-charged by the escorting destroyers. She dives to 230 feet and escapes at two knots speed. Cdr Matsumura later reports one hit on a Colorado-class battleship. During the attack, three torpedoes jam in I-21's tubes and are extracted later.
9 November 1942:
Off Nouméa, New Caledonia. At 1747, I-21 picks up American Liberty ship EDGAR ALLEN POE. Cdr Matsumura makes an approach and fires one torpedo. After the crew leaves the ship, Matsumura closes in to finish her off but is fired at by a deck gun whose crew remained aboard. I-21 dives at once and no further attacks are made. New Zealand minesweeper HMNZS MATAI and corvette KIWI tow POE to Nouméa where she is deemed a total loss.
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's 17th Army garrison on Guadalcanal.
16 December 1942:
At Truk. I-21 tests floating rubber supply containers which are carried on the upper deck and released underwater.
21 December 1942:
Departs Truk for supply missions to Guadalcanal and Buna.
24 December 1942:
Departs Shortland with 20 passengers and rubber supply containers for Guadalcanal. All torpedoes except two are left ashore.
26 December 1942:
At night, arrives at Kamimbo Bay, delivers the food containers and picks up 44 sick soldiers from a Daihatsu barge.
7 January 1943:
Departs Rabaul for the East Coast of Australia with an E14Y1 aboard for her fourth war patrol.
15 January 1943:
I-21 arrives at the prescribed area off Sydney.
18 January 1943:
Tasman Sea, New South Wales, Australia. I-21 sights 2,051-ton Australian freighter KALINGO sailing unescorted from Sydney to New Plymouth, New Zealand. Cdr Matsumura fires two torpedoes, then surfaces. He waits until the crew leaves and then sinks KALINGO with a third torpedo at 34-07S, 153-15E.
That same day, I-21 sights American tanker MOBILUBE proceeding in a convoy. At 2150 (local), I-21 fires two torpedoes at 33-57S, 157-20E. Just when I-21 surfaces to finish her off, she is shelled by a small escort vessel and had to crash-dive. The escort then drops 6 depth charges, but causes no damage. Later, she is towed into port by salvage tug ST. ARISTELLI, but is deemed a total loss.
22 January 1943:
New South Wales, Australia. I-21 torpedoes and damages American Liberty ship PETER H. BURNETT out of Newcastle, Australia, carrying 18,154 bales of wool and 123 bags of mail. Matsumura fires two torpedoes at periscope depth. One hits after a 1 minute 38 sec run. Later, BURNETT is towed to Sydney by minesweeper USS ZANE (DMS-14) and corvette HMAS MILDURA. Most of the cargo is salvaged, but BURNETT is a total loss.
25 January 1943:
I-21 launches her plane for a recce flight over Sydney. The pilot reports the presence of a heavy cruiser and some ten smaller vessels stationed at the harbor entrance.
27 January 1943:
I-21 sights a convoy comprised of three merchants, escorted by a destroyer but is unable to attack.
30 January 1943:
New South Wales, Australia. I-21 attacks British freighter GIANG ANN but her torpedo explodes prematurely and she escapes undamaged.
4 February 1943:
Cdr Matsumura sights a convoy of four merchants, escorted by a destroyer, but is unable to attack.
8 February 1943:
15 miles off Montague Island, New South Wales. I-21 attacks the 10-ship convoy OC68. Cdr Matsumura torpedoes and hits the leading ship in the starboard column of the convoy under the bridge. It is the 4,812-ton British freighter IRON KNIGHT enroute from Whyalla to Newcastle. Laden with iron ore, the ship sinks in two minutes. French destroyer LE TRIOMPHANT arrives and rescues 14 survivors from a raft. Her captain notes that he sighted the convoy from 40 miles away because of its black smoke. He suggests this is possibly the reason so many convoys are being attacked by submarines.
9 February 1943:
I-21 sights a Liberty ship and begins to pursue it.
10 February 1943:
Off Port Macquarire, Australia. I-21 torpedoes and damages American Liberty ship STARR KING en route from Sydney to New Caledonia with 7,000 tons of Army supplies. STARR KING is hit by two of four torpedoes Australian destroyer HMAS WARRAMUNGA rescues the survivors but has to abandon its attempt to tow the crippled freighter. STARR KING sinks at 34-15S, 154-20E.
19 February 1943:
CPO Ito makes another recce flight, taking photos of the New South Wales coast. His plane is detected by radar but is not attacked.
23 February 1943:
Arrives at Truk.
3 March 1943:
Returns to Yokosuka for an overhaul. Cdr Matsumura is credited with five kills.
16 March 1943:
Cdr Inada Hiroshi (51)(former CO of I-2) is appointed CO.
12 May 1943:
I-21 is assigned to the Northern District Force, Fifth Fleet, in Rear Admiral Kouda Takero's SubRon 1 with I-2, I-169, I-171 and I-175. SubRon 1 is given the mission to reinforce and resupply the isolated Japanese garrisons in the Aleutian Islands.
6 May 1943:
Departs Yokosuka on her fifth war patrol.
11 May 1943: American Operation "Sandcrab"- The Invasion of Attu, Aleutians:
Rear Admiral Thomas C. Kinkaid's Task Force 16, covered by Rear Admiral Francis W. Rockwell's Task Force 51, lands the Army's Seventh Division that captures Attu Island, Aleutians.
19 May 1943:
I-21 is ordered to abort her mission and return to Yokosuka in order to participate in the evacuation of Kiska. I-21, I-9 and I-24 are attached to the Fifth Fleet for the duration of the operation.
21 May 1943: Operation "KE-Go": The Evacuation of Kiska:
The Imperial General Headquarters decides to evacuate the garrison at Kiska Island, Aleutians. I-21 departs Yokosuka, participating in two supply missions to Kiska.
26 May 1943:
The evacuation begins from Kiska via submarines to Paramushiro Island, Kuriles.
30 May 1943:
I-21 evacuates 10 midget submarine crews from Kiska.
2 June 1943:
TEIYO MARU refuels I-21, I-7, I-155, I-156 and I-157. P>
18 June 1943:
I-21 returns to Yokosuka to repair her sonar gear. She is fitted with an E27 radar detector and is the first IJN submarine to receive an experimental anti-radar hull coating designated as LI.
15 July 1943:
Rear Admiral Koda orders the evacuation suspended temporarily. All participating submarines are to remain on their positions until further orders.
16 July 1943:
I-21 and I-169 are ordered to shell the P-38 "Lightning" and B-25 "Mitchell" base at Constantine on Amchitka Island. The order is cancelled nine hours later.
9 August 1943:
I-21 returns to Yokosuka.
11 September 1943:
Departs Yokosuka for Truk on her sixth patrol carrying an E14Y1 Glen. She is ordered to reconnoiter Suva.
25 September 1943:
Departs Truk to patrol S of the Fiji Islands.
8 October 1943:
After sundown, I-21 launches her plane for a flight over Suva.
16 October 1943:
Cdr Inada attacks an enemy merchant off New Hebrides with torpedoes but fails to hit her.
19 October 1943:
The I-21 is ordered to intercept a convoy of six fleet oilers earlier sighted by I-36 in the Hawaiian area. She is temporarily subordinated to ComSubDiv 12 aboard I-171 with I-32.
11 November 1943:
I-21 attacks a convoy and torpedoes American freighter CAPE SAN JUAN enroute to Townsville, Australia with 1,348 American troops aboard. Sixteen men are killed when the torpedo hits and another 114 drown after they abandon the ship at 22-08S, 178-06W. Survivors are picked up by Liberty ship EDWIN T. MEREDITH, USS McCALLA (DD-488) and DEMPSEY (DE-26). After reporting his success, Cdr Inada is ordered to return to Truk.
19 November 1943:
En route to Gilberts.
20 November 1943: American Operation "Galvanic" - The Invasion of the Gilberts:
The Americans invade Tarawa and Makin Islands. The invasion fleet of 200 ships includes 13 battleships and 11 carriers.
Vice Admiral (Admiral, posthumously) Takagi Takeo (former CO of MUTSU), Commander, Sixth Fleet (Submarines) orders I-19, I-21, I-35, I-39, I-40, I-169, I-174 and I-175 and RO-38 to proceed to Tarawa to attack the invasion fleet.
27 November 1943:
Gilbert Islands. 30 miles SW of Tarawa. Cdr Inada reports that he has sighted American ships, but this is I-21's last transmission. The report is sent at 1808 (I) from NW of Tarawa.
29 November 1943:
Off Tarawa. Captain D. Ketcham's USS CHENANGO (CVE-28) of Task Group 53.6 is supporting the invasion. At 2157, Grumman "Avenger" torpedo-bombers from CHENANGO's Air Group 35 find and sink a submarine, probably I-21.
30 November 1943:
The CINC, Sixth Fleet, Vice Admiral Takagi orders I-21 and I-35 to report on the situation in the Tarawa landing area, but Cdr Inada does not acknowledge the signal.
24 December 1943:
Presumed lost with all 101 hands in the Gilberts area.
30 April 1944:
Removed from the Navy List.
 In November 1996, a team of marine researchers survey and film the wreck in a small two-person submarine. MONTEBELLO, apparently still loaded with 4.1 million gallons (75,346 barrels) of crude oil, is resting on the sea floor in 900 feet of water adjacent to the Monterey Bay National Marine Sanctuary.
 Some sources claim that PORTER was sunk by I-21, but this is erroneous. In fact, a damaged TBF from ENTERPRISE ditched and its torpedo jarred loose, hit and sank PORTER.
Thanks go to Dr. Higuchi Tatsuhiro of Japan, Steve Eckardt of Australia and Andrew Obluski of Poland.
– Bob Hackett and Sander Kingsepp
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