(KRS Type minelaying submarine scanned from Polmar and Carpenter's "Submarines of the Imperial Japanese Navy")

IJN Submarine I-121:
Tabular Record of Movement

2001-2018 Bob Hackett & Sander Kingsepp
Revision 8

20 October 1924:
Laid down at Kawasaki Kobe Yard as Submarine No. 48.

1 November 1924:
Renamed I-21.

30 March 1926:

20 August 1926:
LtCdr (later Captain) Kobayashi Saburo (37)(former CO of RO-3) is appointed the Chief Equipping Officer (CEO).

31 March 1927:
Completed at Kawasaki Kobe Yard, commissioned in the IJN as I-21 and attached to Kure Naval District. LtCdr Kobayashi Saburo is the Commanding Officer.

15 November 1927:
LtCdr (later Rear Admiral) Nakamura Motoji (39)(former CO of RO-53) is appointed the CO.

9 March 1928:
Off Yokosuka Bay. I-21 is conducting speed trials. About 1100, I-21 collides with destroyer SHIOKAZE on torpedo launch trials. Both ships suffer light damage, but no casualties. I-21 returns to Yokosuka to repair to her bow - bent 60 degrees to starboard.

10 December 1928:
LtCdr (later Rear Admiral) Sato Shiro (43)(former CO of RO-55) is appointed the CO.

15 November 1930:
LtCdr (later Captain) Kijima Moriji (44)(former CO of RO-61) is appointed the CO.

1 December 1931:
LtCdr (later Captain) Minakuchi Hyoe (46)(former CO of RO-51) is appointed the CO.

1 December 1932:
LtCdr (later Captain) Goto Hiroshi (48)(former CO of RO-32) is appointed the CO.

15 March 1933:
Placed in reserve at Kure. LtCdr Goto is appointed the CO of RO-51 (until 1 April) as additional duty.

1 September 1933:
LtCdr (later Captain) Abe Shinobu (42)(current CO of I-22/I-122) is appointed the CO of I-21 as additional duty.

15 November 1933:
LtCdr (later Captain) Takatsuka Tadao (49)(former navigating officer of RO-60) is appointed the CO.

15 November 1934:
LtCdr (Cdr, posthumously) Tsuzuki Noboru (48)(former CO of RO-67) is appointed the CO.

3 July 1935:
LtCdr (Rear Admiral, posthumously) Fujii Akiyoshi (49)(former CO of RO-57) is appointed the CO.

15 November 1935:
Placed in reserve at Kure for the reinforcement of main ballast tanks. LtCdr Akiyoshi is appointed the CO of I-122 as additional duty.

15 February 1936:
LtCdr (later Captain) Nakagawa Hajime (50)(former CO of RO-64) is appointed the CO of I-121 and I-122 (until 30 June) as additional duty.

20 March 1937:
LtCdr (later Captain) Yamada Kaoru (50)(former CO of RO-63) is appointed the CO.

7 July 1937: The Marco Polo Bridge (The "First China Incident"):
Hun River, Lugouqiao, China. Japanese troops on night maneuvers fire blank cartridges. Nearby Chinese troops fire back, but do not cause injuries. At morning roll call, the Japanese discover a soldier missing and assume the Chinese captured him. They demand entry to a Peking suburb to look for the soldier. The Chinese refuse. The Japanese then shell the city and an undeclared war on China begins.

September 1937:
SubDiv 13 with I-21 and I-22 joins the naval blockade over the southern Chinese coast while based at Tsingtao.

3 February 1938:
I-21 and I-22 are assigned to provide distant cover for the light cruiser KUMA (current flagship of SubRon 3), tasked with landing a SNLF unit off Chefoo. Neither submarine is able to sortie as a result of problems with their diesel engines.

19 March 1938:
LtCdr (Captain, posthumously) Koike Iitsu (52)(former damage control officer of SATA) is appointed the CO.

22 March 1938:
Shantung province, NE China. I-21 and I-22 land a force of 30 Shanghai Special Naval Landing Force (SNLF) troops on Liugong (Liukung) Island in Weihai Bay.

1 June 1938:
I-21 is renumbered I-121.

30 July 1938:
LtCdr (Captain, posthumously) Hanabusa Hakushi (51)(former CO of RO-63) is appointed the CO.

10 March 1939:
LtCdr Hanabusa is appointed the CO of I-64 as additional duty.

20 March 1939:
LtCdr (later Cdr) Kusaka Toshio (53)(former torpedo officer of I-2) is appointed the CO.

29 July 1939:
LtCdr (later Captain) Yoshitome Zennosuke (52)(current CO of I-122) is appointed the CO of I-121 as additional duty.

16 August 1939:
LtCdr (later Captain) Otani Kiyonori (49)(former CO of I-69) is appointed the CO.

24 October-15 November 1939:
LtCdr (promoted Cdr 15 November) Otani is appointed the CO of I-67 as additional duty.

The entire I-121 class is converted to carry 15 tons of aviation fuel for Kawanishi H6K Type 97 "Mavis" flying boats.

30 October 1940:
LtCdr (later Captain) Inaba Michimune (51)(former CO of I-70) is appointed the CO.

30 January-4 February 1941:
I-121 is designated as the temporary flagship of SubDiv 13 instead of the I-122.

31 January 1941:
LtCdr (later Cdr) Kono Masamichi (52)(former CO of I-62) is appointed the CO.

1 May 1941:
I-121 is assigned to the Third Fleet in Rear Admiral Kono Chimaki's SubRon 6 under Captain (Rear Admiral, posthumously) Miyazaki Takeji's SubDiv 13 with I-122.

2 June 1941:
Cdr (promoted Cdr 15 October; Captain, posthumously) Endo Shinobu (52)(former CO of I-59) is appointed the CO.

November 1941:
I-121, under Cdr Endo Shinobu, departs Yokosuka for Samah, Hainan Island, China.

1 December 1941:
Departs Samah.

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.

6 December 1941: Operation "M" - The Attack on the Southern Philippines:
Vice Admiral Takahashi Ibo's (35)(former CO of KIRISHIMA) Second Fleet, Southern Force, Philippines Seizure Force departs Palau.

7 December 1941:
I-121 and I-122 lay two minefields NE of Singapore. I-121 lays 42 Type 88 Mk. 1 mines in the approximate area of 0-40N, 115E and then commences her first war patrol off the eastern entrance of Johore Strait.

11 December 1941:
Vice Admiral Takahashi's force invades Legaspi, covered by light carrier RYUJO, CruDiv 5's HAGURO, MYOKO, NACHI, DesRon 2's light cruiser JINTSU and nine destroyers and Rear Admiral (later Vice Admiral) Kubo Kyuji's (35)(former CO of MIKUMA) seaplane tenders CHITOSE, MIZUHO, light cruisers NAKA, NAGARA, five destroyers and seven transports.

12 December 1941:
Arrives at Camranh Bay; departs later that day for Davao, Philippines. Reassigned to Southern Submarine Force with I-122.

19-20 December 1941:
Takahashi's force invades Davao, Philippines.

24 December 1941:
Takahashi's force invades Jolo, Philippines.

26 December 1941:
Reassigned to Submarine Group "A" with I-122 through I-124.

27 December 1941:
Arrives at Davao, Mindanao Island.

5 January 1942:
Departs Davao in company of I-122 on her second war patrol to lay a minefield off Port Darwin, Australia, the U.S. Asiatic Fleet's main logistics base.

11 January 1942:
Timor Sea, SW of Tiwi Islands. At 0530, Cdr Endo attacks an unidentified Allied destroyer.

12 January 1942:
Clarence Strait. By 0455, I-121 lays 39 mines and then returns to her former station in Timor Sea.

18 January 1942:
Timor Sea, N of Wetar Island. I-121 chases an unidentified Allied merchant escorted by a small patrol vessel and attacks it with three torpedoes. Following this attack, I-121 returns to Clarence Strait. [1]

21 January 1942:
Clarence Strait, off Darwin. I-121 is chased by several patrol vessels, dropping a total of 42 depth charges. She receives medium damage to two fuel tanks, but escapes. [2]

25 January 1942:
Departs the patrol area, heading for the scheduled rendezvous area with I-124.

28 January 1942:
At 0400, I-121 arrives at the rendezvous area and remains there until 2300. After I-124 fails to show up, I-121 continues her voyage for Davao.

30 January 1942:
After the loss of I-124, SubRon 6's I-121 and I-122 arrive at Davao, Philippines. They are serviced by tender CHOGEI. I-121's damaged fuel tanks are repaired.

1 February 1942:
LtCdr (later Cdr) Fujimori Yasuo (56)(former CO of RO-60) is appointed the CO.

9 February 1942:
Departs Davao in company of I-122 on her third war patrol to reconnoiter Port Darwin prior to the attack of Vice Admiral (Admiral, posthumously) Nagumo Chuichi's (36) Striking Force and transmit weather reports.

I-121 and I-122 depart Davao. I-121 is to act as a weather ship in the Arafura Sea. She patrols 300 miles NE of Morotai.

13 February 1942:
I-122 detaches and proceeds SE. I-121 continues south.

16 February 1942:
By sundown I-121 arrives at her assigned area 50 miles NW of Darwin.

18 February 1942:
I-21 surfaces on station prior to sunset to recharge her batteries, but is strafed by an Australian patrol plane. Fujimori crash-dives. After dark he resurfaces and at 2030 sends a weather report that is relayed to Vice Admiral Nagumo's Strike Force then en route from Palau.

19 February 1942: The Attack on Darwin:
At 0230 Fujimori sends a second weather report. At 0957 (local), Nagumo's Striking Force raids Port Darwin. Seventy-one "Kate" attack planes, 81 "Val" dive-bombers and 36 "Zeke" fighters led by Cdr (later Captain) Fuchida Minoru (of Pearl Harbor) from CarDiv 1's AKAGI and KAGA and CarDiv 2's HIRYU and SORYU attack Darwin.

They destroy 15 aircraft including nine American Curtiss P-40 "Kittyhawk" fighters, sink eight ships including destroyer USS PEARY (DD-226) and large Army transport GENERAL M.C. MEIGS, damage nine ships including seaplane tender (WW1 destroyer conversion) USS WILLIAM B. PRESTON (AVD-7).

The carrier strike is followed by a strike of 28 twin-engine land-based Mitsubishi G3M2 "Nells" of the 1st Kokutai from Ambon and 27 Mitsubishi G4M1 "Bettys" of the Kanoya Kokutai, based at Kendari, Celebes.

25 February 1942:
I-121 departs her patrol station.

28 February 1942:
I-121 arrives at Staring (Teluk) Bay, near Kendari and refuels. SubRon 6's boats are serviced by CHOGEI that arrived earlier from Davao.

10 March 1942:
I-121 and I-122 depart Staring Bay for Japan. On that same day, both submarines are directly attached to the Combined Fleet HQ.

21 March 1942:
Arrives at Kure for repairs.

8 May 1942: Operation "MI": The Battle of Midway:
Departs Kure for Kwajalein.

10 April 1942:
SubRon 6 is disbanded. SubDiv 13 is attached directly to the Sixth Fleet.

19 May 1942:
Arrives at Kwajalein.

21 May 1942:
Departs Kwajalein for the French Frigate Shoals to participate in Operation K-2.

30 May 1942:
I-121 receives I-123's message about American vessels sighted at French Frigate Shoals.

31 May 1942:
I-121 and I-123 are ordered to continue to patrol in the vicinity of the Shoals.

1 June 1942:
Departs French Frigate Shoals and heads west.

4 June 1942:
I-121 and I-123 receive the order to proceed westward.

5 June 1942:
SW of Lisianski Island. I-121 briefly sights a surfaced American submarine, heading NE, but fails to reach the firing position. [3]

25 June 1942:
Arrives at Kwajalein in company of I-122 and I-123, later returns to Yokosuka.

14 July 1942:
Captain Miyazaki Takeji's SubDiv 13 is reassigned to SubRon 7, Eighth Fleet.

16 July 1942:
Departs Yokosuka for Truk in company of I-122.

24 July 1942:
Arrives at Truk.

31 July 1942:
Departs Truk for Rabaul.

4 August 1942:
Arrives at Rabaul.

7 August 1942 - American Operation "Watchtower" - The Invasion of Guadalcanal, Solomons:
Rear Admiral (later Admiral) Richmond K. Turner's (USNA '04) Amphibious Task Force 62, covered by Vice Admiral (later Admiral) Frank J. Fletcher's (USNA '06) Task Force 61 and Rear Admiral (later Admiral) John S. McCain's (USNA '06) Task Force 63's land-based aircraft, lands Maj Gen (later General/Commandant) Alexander A. Vandegrift's 1st Marine Division on Florida, Tulagi, Gavutu, Tanambogo and Guadalcanal opening a seven-month campaign to take the island.

That day, I-121 and I-122 depart Rabaul to reconnoiter Guadalcanal and Tulagi.

8 August 1942:
30 miles S of Cape St. George, New Ireland. Lookouts aboard LtCdr (later Captain) Henry G. Munson's (USNA '32) USS S-38 spot the I-121 en route on the surface from Rabaul to Savo Island, but Munson is unable to attack.

15-17 August 1942:
Reconnoiters Lunga anchorage.

18 August 1942:
I-121 is redirected to a new patrol area SE of San Cristobal.

21 August 1942:
SubRon 7 is reassigned to the Advance Force.

22 August 1942:
50 miles SE of San Cristobal. At 1710, I-121 attacks Rear Admiral Thomas C. Kinkaid's Task Force 16. One torpedo passes between USS ENTERPRISE (CV-6) and heavy cruiser USS PORTLAND (CA-33), broaching briefly.

24 August 1942: The Battle of the Eastern Solomons:
Vice Admiral (later Admiral) Frank J. Fletcher's Task Force 61's USS SARATOGA (CV-3) and ENTERPRISE launch aircraft that find and sink light carrier RYUJO. In turn, CarDiv 1's SHOKAKU and ZUIKAKU launch aircraft that find and damage ENTERPRISE. That evening, aircraft from SARATOGA damage the seaplane carrier CHITOSE.

26 August 1942:
I-121 receives the order to proceed southward in an attempt to intercept the damaged USS ENTERPRISE.

27 August 1942:
175 miles SW of San Cristobal. At 0630, when recharging batteries, I-121 is caught on the surface by two Douglas SBD-3 "Dauntless" dive-bombers from USS WASP (CV-7). While diving, she receives a bomb hit to her empty mine storage compartment, causing a serious leak. The crippled submarine surfaces a few hours later to execute emergency repairs. The damage makes diving impossible and I-121 is forced to operate surfaced (although being trimmed down) thereafter.

29 August 1942:
80 miles NE of San Cristobal. At 0430, I-121 sights one carrier and several destroyers; at 0800 she sights one carrier, two cruisers and four destroyers.

4 September 1942:
At 1500, returns to Rabaul for repairs.

8 September 1942:
Departs Rabaul.

20 September 1942:
Returns to Kure for an overhaul.

15 October 1942:
Lt (promoted LtCdr 1 November; Cdr, posthumously) Shimada Takeo (59)(former RO-62) is appointed the CO.

16 November 1942: Vice Admiral Komatsu convenes a meeting of his submarine captains at Truk. He announces that the Sixth Fleet has been ordered by Admiral (Fleet Admiral posthumously) Yamamoto Isoroku (32), CINC, Combined Fleet, to organize a supply system for the IJA's 17th Army garrison on Guadalcanal.

1 December 1942:
Departs Kure for Truk.

10 December 1942:
Arrives at Truk.

17 December 1942:
Departs Truk for Rabaul.

21 December 1942:
Arrives at Rabaul. Reassigned to Submarine Group "B".

23 December 1942:
Departs Rabaul on her first supply run to Buna, eastern New Guinea.

28 December 1942:
Reassigned to Submarine Group "D".

4 January 1943:
Departs Rabaul to patrol SE of New Guinea.

25 January 1943:
Returns to Rabaul.

29 January 1943:
Departs Rabaul to refuel the IJN reconnaissance floatplanes at the Indispensable Reef.

10 February 1943:
Returns to Rabaul.

14 February 1943:
Departs Rabaul for Truk.

18 February 1943:
Arrives at Truk.

23 February 1943:
Departs Truk for Kure.

5 March 1943:
Arrives at Kure for overhaul.

15 April 1943:
SubRon 7 is reassigned to the Southeast Area Fleet.

25 April 1943:
Departs Kure.

7 May 1943:
Arrives at Rabaul.

10 May 1943:
Departs Rabaul on her first supply run to Lae, New Guinea.

14 May 1943:
Arrives at Lae, unloads 26 tons of food and ammunition. Embarks 15 soldiers, then departs for Rabaul.

17 May 1943:
Returns to Rabaul.

19 May 1943:
Departs Rabaul on her second supply run to Lae.

22 May 1943:
Returns to Rabaul after aborting the sortie because of engine troubles.

23 May 1943:
Departs Rabaul on her third supply run to Lae.

26 May 1943:
Arrives at Lae, unloads 26 tons of food and ammunition, then departs for Rabaul.

29 May 1943:
Returns to Rabaul.

31 May 1943:
SubDiv 13 is disbanded. I-121 and I-122 are attached to SubRon 7 HQ.

1 June 1943:
Departs Rabaul on her fourth supply run to Lae.

3 June 1943:
Arrives at Lae, unloads 26.5 tons of food and ammunition. Embarks 15 soldiers, then departs for Rabaul.

6 June 1943:
Returns to Rabaul.

8 June 1943:
Departs Rabaul on her fifth supply run to Lae.

10 June 1943:
Arrives at Lae, unloads 26.5 tons of food and ammunition. Embarks 15 soldiers, then departs for Rabaul.

13 June 1943:
Returns to Rabaul.

20 June 1943:
Departs Rabaul on her sixth supply run to Lae.

22 June 1943:
Arrives at Lae, unloads 26.5 tons of food and ammunition, then departs for Rabaul.

7 July 1943:
Arrives at Lae on her seventh supply run.

27 July 1943:
Arrives at Lae on her eighth supply run.

3 August 1943:
Arrives at Lae on her ninth supply run.

15 August 1943:
I-121 and I-122 are reassigned to Kure Guard Unit.

19 August 1943:
Departs Rabaul.

20 August 1943:
Arrives at Lae on her tenth supply run there. On that same day, Lt (Cdr, posthumously) Watanabe Masaki (63)(former torpedo officer of I-171) is appointed the CO.

1 September 1943:
Returns to Kure. I-121 and I-122 are withdrawn from combat and assigned to training duties at the Kure Naval Base thereafter.

December 1943:
I-121 is in SubDiv 18 with I-122 and I-153, I-154 and I-155. Continues training duties.

5 January 1944:
Iyo Nada, Inland Sea. I-121 participates in the first stage of submarine camouflage pattern experiments (Gaigen Toshoku Jikken) conducted by the Naval Submarine School. She and I-159 receive No. 5 scheme (probably a greenish gray pattern), applied to the hull and conning tower sides.

23 February 1944:
Cdr (later Captain) Inaba Michimune (51)(former CO of I-36) is appointed the CO (his second tour as the CO of that boat).

10 January 1945:
Lt (promoted LtCdr 5 September) Ueno Tadahiro (66)(former assistant instructor at submarine school) is appointed the CO.

20 April 1945:
Reassigned to SubDiv 33 with I-122.

23-25 February 1945:
Iyo Nada. I-121 and I-159 participate in the second stage of submarine camouflage pattern experiments, featuring No. 5 scheme, now extending to the wooden deck surfaces.

12 June 1945:
Transferred to the Maizuru Naval Base, Honshu in the Kure SubRon's SubDiv 33. Remains there until the end of the war.

15 August 1945:
Emperor Hirohito (Showa) broadcasts an Imperial Rescript that calls for an end to hostilities.

September 1945:
I-121 surrenders at Maizuru.

13 October 1945:
At Maizuru with I-201, I-202 and RO-500.

30 November 1945:
Removed from the Navy List.

30 April 1946:
Scuttled in Wakasa Bay off Kanmuri Jima with RO-68 and RO-500.

(I-121, RO-68 and RO-500's final day at Maizuru)

18-21 June 2018:
The Society La Plongée for Deep Sea Technology research team headed by Research Professor Ura Tamaki from Kyushu Institute of Technology locates and photographes the wrecks of I-121, RO-68 and RO-500, using a multibeam echosounder and an ROV. The wreck of I-121 is located at the depth of 300 ft.

Authors' Note:
[1] Several historians have credited I-121 with sinking the Dutch merchant BANTAM (the same name is redered as VAN DAM in some sources). This is incorrect, since BANTAM was not in that area; she also survived the war.

[2] I-121's attackers at that time were most likely USS ALDEN (DD-211), EDSALL (DD-219), HMAS DELORAINE and KATOOMBA, all participating in the hunt for a submarine sighted off Cape Fourcroy, Bathurst Island, 60 miles NW of Darwin.

[3] Probably USS DOLPHIN (SS-169), who in turn reported sighting a periscope at 1459 (Y) when changing her assigned patrol station. At the time of sighting I-121 was 2,000 yds dead astern of her opponent, who moved out of the range before a firing solution could be acquired.

Thanks go to Dr. Higuchi Tatsuhiro of Japan and Steve Eckardt of Australia.

Special thanks go to author John B. Lundstrom for sharing his research on carrier operations off Guadalcanal.

- Bob Hackett and Sander Kingsepp.

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