SENSUIKAN!

© 2001-2016 Bob Hackett & Sander Kingsepp
Revision 4

4 February 1943:
Laid down at Kawasaki's Kobe Yard as Submarine No. 621, the first A Modified class submarine. The AM-class will carry two Aichi M6A1 Seiran (Mountain Haze) float torpedo-bombers capable of carrying either 1,764 lbs of bombs or a 45 cm (17.7-inch) torpedo 654 miles.

During her construction it is planned to use I-13 to launch a surprise air strike against the Panama Canal's Gatun Locks. The plan is to assign ten Seirans to strike the Locks with six torpedoes and four bombs. Destroying these locks would empty Gatun Lake and block the passage of shipping for months.

1 October 1943:
Renumbered I-13 and provisionally attached to Sasebo Naval District.

30 November 1943:
Launched.

10 September 1944:
Cdr (Captain, posthumously) Ohashi Katsuo (53) (former CO of I-54) is appointed Chief Equipping Officer.

16 December 1944:
I-13 is completed and attached to Sasebo Naval District. Cdr Ohashi is the Commanding Officer. I-13 is assigned to the Sixth Fleet in Captain Ariizumi Tatsunosuke's (former CO of I-8) SubDiv 1. I-13 departs Kobe that day for Kure.

17 December 1944:
Arrives at Kure. Commences basic sea training.

January 1945:
Western Inland Sea. I-13 begins workup and battle training at SubRon 11 with I-400, but the war situation has changed and the Panama Canal operation is discarded.

19 January 1945:
Before destroyers KAMIKAZE and NOKAZE depart home waters, I-13 briefly acts as an ASW target for their crews.

9/10 March 1945: The First Fire Bombing of Tokyo:
B-29s of MajGen (later Gen/CSAF) Curtis E. LeMay's Twentieth Air Force's XXI Bomber Command take off from Guam, Tinian and Saipan. 280 B-29's bomb Tokyo by radar at night. Dropping 1,900 tons of incendiaries from altitutes of 4,500-9,000 ft, they burn out about one-fourth of the city. At least 83,000 people die in the raid, the highest death toll of any day in the war, including deaths caused by the atomic bombs.

March-April 1945:
In retaliation for the fire bombing of Tokyo, the Imperial Naval General Staff considers a proposal from the Sixth Fleet to use I-400's to bomb San Francisco. The proposal is opposed by Vice Admiral Ozawa Jisaburo (former CO of HARUNA), Vice Chief, NGS.

19 March 1945:
Vice Admiral (later Admiral) Marc A. Mitscher's Task Force 58 carriers USS ESSEX (CV-9), INTREPID (CV-11), HORNET (CV-12), WASP (CV-18), HANCOCK (CV-19), BENNINGTON (CV-20) and BELLEAU WOOD (CVL-24) make the first carrier attack on the Kure Naval Arsenal.

More than 240 aircraft (SB2C "Helldivers", F4U "Corsairs" and F6F "Hellcats") attack battleships HYUGA, ISE, YAMATO, HARUNA, carriers AMAGI, KATSURAGI, RYUHO, KAIYO and other ships.

I-13 submerges and escapes damage, but I-400 (in drydock) and I-401 are strafed.

1 April 1945:
Vice Admiral (later Admiral) Raymond A. Spruance's Fifth Fleet, including more than 40 aircraft carriers, 18 battleships, 200 destroyers and over 1,000 support ships surround Okinawa. LtGen Simon B. Buckner Jr's Tenth Army (7th, 77th, 96th Infantry, 1st, 6th Marine divisions) makes amphibious landings and begins the campaign to take the island from LtGen Ushijima Mitsuru's 32nd Army.

27 May 1945:
SubDiv 1's I-13 and I-14, I-400 and I-401 are equipped with new snorkels.

At 0800, I-13 and I-14 depart Kure through the heavily mined Shimonoseki and Tsushima Straits in the Sea of Japan and head for Chinkai (now Jinhae), South Korea to refuel.

At 1900, arrive at Moji, Kyushu, for an overnight stop.

28 May 1945:
I-13 and I-14 arrive at Chinkai.

29 May 1945:
I-13 and I-14 depart Chinkai for Nanao Bay, Honshu.

1 June 1945:
Dense fog en route forces Cdr Ohashi to stop at Toyama Bay, Honshu.

3 June 1945:
Arrives at Nanao Bay for battle training. SubDiv 1's training is hampered by mines, American submarines and shortages of aviation gasoline, material and aircraft, but they manage to launch a number of simulated air strikes.

12 June 1945:
The Imperial High Command decides to use SubDiv 1 to attack the American naval anchorage at Ulithi Atoll because of the imminent fall of Okinawa and the carrier raids on Japan.

20 June 1945:
Both "Seiran" torpedo-bombers are landed. I-13 and I-14 depart Nanao Bay for Maizuru.

21 June 1945: The Fall of Okinawa:
Eighty-two days after the initial landings, Okinawa is declared secure.

22 June 1945:
I-13 arrives at Maizuru.

25 June 1945: Operation "ARASHI" (Mountain Storm) - The Attack on Ulithi:
At 1325, Vice Admiral Ozawa, now CINC, Combined Fleet, issues Battle Order No. 95 that details the impending operation. The bombing attack is designated as Operation ARASHI.

The "HIKARI" (Shining Light) part of Operation ARASHI calls for I-13 and I-14 to proceed to Truk in late July and deliver their Nakajima C6N1 "Saiun" Myrt long range reconnaissance aircraft. The aircraft will then be assembled and used to reconnoiter Ulithi. The "Myrts" are to relay target information on American aircraft carriers and troop transports to I-400 and I-401's six "Seiran" torpedo-bomber crews for a strike on 17 August.

The attack is to be made under a full moon. Prior to the start of the attack, the pilots are to receive a special hormone injection to enhance their night vision. The "Seirans" are tasked to each carry an 800-kg bomb and land near their submarines. After the attack, all four of SubDiv 1's boats are to proceed to Singapore, refuel and embark new planes for the new attack. Ten "Seirans" are to be stationed there prior to the attack on Ulithi.

2 July 1945:
Departs Maizuru.

4 July 1945: Operation HIKARI:
I-13 arrives at Ominato Naval Base on the northern tip of Honshu. She embarks two crated "Myrts".

11 July 1945:
At 1500, I-13 departs Ominato for Truk. Her estimated time of arrival at Truk is 20 July. There is no further contact with I-13.

On that same day, FRUMEL intercepts a message from I-13, timed 101513, providing the approximate noon positions for 13, 15 and 18 July, which cannot be deciphered. FRUMEL concludes that Operation "HIKARI" involves the transportation of about 4 suicide aircraft to Singapore.

16 July 1945:
550 miles E of Yokosuka. At 0747, the radarman in Lt (j.g.) William McLane's Grumman TBM-3E "Avenger" from VC-13 of Task Group 30.7's USS ANZIO (CVE-57) picks up a Japanese submarine running on the surface. McLane opens fire with his .50 cal. machine guns and 5-inch rockets. The submarine dives, but leaves a trail of oil on the surface. McLane drops Mk. 54 depth charges, then sonobuoys and a Mk. 24 "Fido" acoustic homing torpedo.

Later, two more Avengers from ANZIO's aircraft relieve McLane. They drop more sonobuoys and another "Fido" on the submerged submarine. Later, the aircraft guide LtCdr J. R. Grey's LAWRENCE C. TAYLOR (DE-415) to the heavy oil slick that marks the submarine's position. At 1140, TAYLOR attacks with a barrage of twenty-four 7.2-inch Mk. 10 "Hedgehog" projector charges that sink the submarine - probably I-13 - at 34-28N, 150-55E.

31 July 1945:
At 1033, USN codebreakers intercept and decrypt a message that reads: "Since the I-13 sortied from Ominato July 11th, have had no communication with her. This unit ----- has no knowledge of what happened to her."

1 August 1945:
Presumed lost with all hands in the Truk area.

15 September 1945:
Removed from the Navy List.

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Authors' Notes:
[1] I-13's crew of 140 was the largest human loss in the IJN submarine force during the war.

Thanks go to Dr. Higuchi Tatsuhiro of Japan. Thanks also go to John Whitman of the USA for info on CNO intercepts of Japanese messages and to Hans Mcilveen of the Netherlands for info on FRUMEL intercepts.

– Bob Hackett & Sander Kingsepp

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