Imperial Japanese Navy - HEI-GATA type Submarine ==========================================================================




The Cruiser submarine Type-C (Junsen Hei-gata) was a class of submarine the Imperial Japanese Navy (IJN) built to serve during the Second World War. The Hei-gata type cruiser submarines were based on the Junsen type 3 (I-7 class) design. Type-C submarines were better armed than the Type-A (Junsen) submarine and Type-B (Kaidai) submarine. Hei-gata (Junsen C3 type) submarines were operated by the Imperial Japanese Navy and were designed to be primarily used as cargo carriers. The Type-C submarines were also utilized as Kō-hyōteki mother ships or Kaiten mother ships, for this reason they were not equipped with aviation facilities like some of the other two Junsen class types.

The Hei-gata class of submarines was designed and built by Mitsubishi Corporation, between 1943 and 1944, as cargo carriers. They were quite long and carried a crew of up to 94. They also had a long cruising range at a speed of 12 knots (22 km/h). The Japanese completed only three of these during World War II (I-52, I-53 and I-55), although twenty were planned. They were among the largest submarines ever built to date at the time of their construction, and were known as the most advanced submarines of the period.


I-52, code-named Momi ("evergreen" or "fir tree") was a Junsen Type C-3 (Hei-gata) cargo submarine of the Imperial Japanese Navy. I-52 was laid down on 18 March 1942, and she was commissioned on 28 December 1943 into the 11th Submarine Squadron. After training in Japan she was selected for a Yanagi (exchange) secret mission to Lorient, France, then occupied by Germany, during which she was sunk on 24 June 1944 by aircraft from USS Bogue (CVE-9) 800 mi (1,300 km) southwest of the Azores. Her cargo consisted of rubber, gold, quinine, and Japanese engineers being sent to Germany.

Yanagi (exchange) missions were enabled under the Axis Powers' Tripartite Pact to provide for an exchange of strategic materials and manufactured goods between Germany, Italy and Japan. Initially, cargo ships made the exchanges, but when that was no longer possible submarines were used.

She is also known as Japan's "Golden Submarine", because she was carrying a cargo of gold to Germany as payment for war material and technology. There has been speculation that a peace proposal to the allies was contained onboard the I-52 as well, but this is highly unlikely on two counts: 1) there is no evidence of the Japanese government being interested in peace proposals or negotiated settlements at this early stage in the war, prior to the summer of 1945, and 2) the Japanese kept an open dialogue with their diplomatic attaches via radio and diplomatic voucher through Russia, and had no need for long and uncertain transfer via submarine.

On 10 March 1944, on her maiden voyage, I-52 (Commander Uno Kameo) departed Kure via Sasebo for Singapore. Her cargo from Japan included 9.8 tons of molybdenum, 11 tons of tungsten, 2.2 tons of gold in 146 bars packed in 49 metal boxes, 3 tons of opium and 54 kg of caffeine. The gold was payment for German optical technology. She also carried 14 passengers, primarily Japanese technicians, who were to study German technology in anti-aircraft guns, and engines for torpedo boats.

In Singapore she picked up a further 120 tons of tin in ingots, 59.8 tons of caoutchouc (raw rubber) in bales and 3.3 tons of quinine, and headed through the Indian Ocean, to the Atlantic Ocean.

On 6 June 1944, the Japanese naval attaché in Berlin, Rear Admiral Kojima Hideo, signaled the submarine that the Allies had landed in Normandy, thus threatening her eventual destination of Lorient on the coast of France. She was advised to prepare for Norway instead. She was also instructed to rendezvous with a German submarine on 22 June 1944 at 21:15 (GMT) at the co-ordinates 15°N 40°W / 15°N 40°W / 15; -40. I-52 responded with her position, being 35°N 23°W / 35°N 23°W / 35; -23. The message was intercepted and decoded by US intelligence; I-52 had been closely watched all the way from Singapore. Guided by the F-21 Submarine Tracking Room and F-211 "Secret Room" of the Tenth Fleet which was in charge of the Atlantic section, a hunter-killer task force was targeted towards her.

A US task force assembled as a submarine hunter-killer group, consisting of the escort carrier USS Bogue and five destroyers, en route to the United States from Europe, was ordered to find and destroy the Japanese submarine. This task force departed from Casablanca on 15 June 1944, and was commanded by Captain Aurelius B. Vosseller. It also had 9 FM-2 Wildcats and 12 TBF-1C Avenger of VC-69 on board. The task force, on its way from Hampton Roads to Casablanca, had sunk another Japanese submarine, the Type IX RO-501 (formerly U-1224) on 13 May 1944. This was a very effective force, sinking 13 German and Japanese submarines between February 1943 and July 1945.

On the night of 22 June 1944 about 850 nautical miles (1,574 km) west of the Cape Verde Islands off the coast of Africa, I-52 rendezvoused with U-530, a Type IXC/40 U-boat commanded by Kapitänleutnant Kurt Lange. U-530 provided her with fuel, and also transferred a Naxos FuMB 7 radar detector, and an Enigma coding machine, along with two radar operators and a German liaison officer for the trip through the Bay of Biscay.

Arriving in the area of the meeting, the US carrier began launching flights of Avengers at around 23:00 GMT to search for the submarines. U-530 escaped undetected. I-52 was not to be so lucky.

At approximately 23:40 on 23 June, Ed Whitlock, the radar operator in Lieutenant Commander Jesse D. Taylor's Avenger, detected a surface contact on his malfunctioning radar (only the right half of its sweep was working). Taylor immediately dropped flares, illuminating the area, and attacked. After his first pass, he saw the depth charge explosions just to starboard of the submarine — a near miss — and the submarine diving. Taylor dropped a purple sonobuoy, a newly-developed device that floated, picked up underwater noise, and transmitted it back. A searching aircraft usually dropped these in packs of five, named purple, orange, blue, red and yellow (POBRY); the operator was able to monitor each buoy in turn to listen for sounds emitted by its target.

Taylor then began a torpedo attack, dropping a Mark 24 "mine" torpedo. That term was used for what was code-named "Fido": the first Allied acoustic torpedo, developed by the Harvard Underwater Sound Lab, which homed in on the sounds of the submarine. Fido was designed to be a "mission kill" weapon — it would damage the submarine so badly it would have to surface, rather than destroying it completely. Within minutes, the sonobuoys transmitted the sounds of an explosion and mechanical break-up noises.

As Commander Taylor's watch ended, the operators on Bogue and Taylor all thought he had sunk the sub. However, as Taylor's patrol ended, he was relieved by Lieutenant (junior grade) William "Flash" Gordon, accompanied by civilian underwater sound expert Price Fish. They arrived on the scene just after midnight, and circled with Taylor for some time. At about 01:00 on 24 June 1944, Fish reported hearing some faint propeller noise in the area.

Captain Vosseller ordered a second attack; Gordon checked with Taylor about the exact position of the sonobuoy, and dropped another "Fido" torpedo where he believed the submarine to be. Taylor departed from the area at 01:15, but Gordon stayed to circle the area and listen for any sign of activity. He heard nothing, and was relieved by Lieutenant (junior grade) Brady, who continued to watch and listen, but no further activity was reported. Next morning, Janssen reached the site and found flotsam: a ton of raw rubber, a piece of silk, and even human flesh.

The sonobuoy recording of the last few moments of I-52's sound still survives in the US National Archives in Washington D.C. in the form of two thin film canisters marked "Gordon wire No. 1" and "Gordon wire No. 2" dated 24 June 1944. The wire from Taylor's attack has not been found; however, a set of 78 rpm vinyl recordings that include segments of Taylor's wire recordings has been located. These records were produced during the war for training pilots. On the wire and vinyl recordings Lieutenant Gordon can be heard talking to his crew, along with the sound of a torpedo exploding, and metal twisting. [4] Subsequent to the discovery of the wreck (see below), analysts at the Johns Hopkins University Applied Physics Laboratory, experts in analyzing modern submarine sounds, studied these recordings and concluded that the I-52 was sunk by Taylor. The propeller sounds heard by Gordon were actually from the U-Boat, nearly 20 miles (32 km) away, reaching Gordon's sonobuoys through a "surface duct". This quirk of underwater sound propagation traps sounds in a channel near the surface and can transmit them for many miles. At the time, the Navy credited the sinking of the I-52 to both Gordon and Taylor, as it was uncertain whether the ship was sunk on the first attack.

On 30 August 1944, the Kriegsmarine officially declared I-52 sunk in the Bay of Biscay as of 25 July 1944, with all crew. The Imperial Japanese Navy declared I-52 missing on 2 August 1944, and struck her from service on 10 December 1944 as sunk.

Also interesting is that 800 kg of uranium oxide awaited I-52 at Lorient for her return voyage according to Ultra decrypts. It has been speculated that this was for the Japanese to develop a radiological weapon (a so-called "dirty bomb") for use against the United States (the amount of unenriched uranium oxide would not have been enough to create an atomic bomb, though if used in a nuclear reactor it could have created poisonous fission by-products).

She was also to be fitted with a german snorkel device while at Lorient.

Only six submarines attempted this trans-oceanic voyage during World War II: Kaidai I-30 (April 1942), Junsen I-8 (June 1943), the German submarine U-511 (August 1943), Kaidai I-34 (October 1943), and Kaidai I-29 (November 1943).

Of these, I-30 was sunk by a mine, I-34 by the British submarine Taurus, and I-29 by the American submarine, Sawfish (assisted by Ultra intelligence). Hei-gata I-52 was the final submarine to attempt the voyage.


In late 1994, a salvage operation named Project Orca was launched to try and locate the I-52 and retrieve her valuable cargo of gold. Despite the commissioning of the Russian research ship Akademik Keldysh for the project, and an extensive search, by March 1995 the search proved to be a failure.

Very shortly afterwards, however, in the spring of 1995 Paul Tidwell, working with the ocean exploration company Meridian Sciences, Inc. (later renamed Nauticos Corp.) located the wreck 5,240 meters deep, mostly upright. The vessel was found nearly 20 miles (32 km) from the datum quoted by the U.S. Navy at the time of the sinking, but within 1/2 mile of the coordinates computed by Meridian. Meridian's analysts used historical ship logs from the U.S. task force as well as from the German U-Boat to reconstruct the events of the battle, and correct navigation errors using a process called "re-navigation," or RENAV. Her conning tower is intact and her hull number is still visible. The bow is broken up, probably due to impact on the bottom, and a large hole, undoubtedly caused by one of the torpedoes, is aft of the conning tower. Debris was scattered over a large area. Plans were made to raise the sub and recover the gold. The Japanese government objected, indicating that they considered the wreck site a grave. Tidwell worked out the proper procedures with the Japanese government and received the approval of the war graves authorities in Japan. Tidwell's team also took down a Japanese naval ensign and affixed it to the wrecked submarine. A metal box from the debris field was brought to the surface in the hope that it would contain some of the sunken gold (then worth US$25 million), but when opened, the salvagers were disappointed to find not gold, but opium. It was dumped overboard.

The plan was to recover the entire conning tower, diplomatic pouches, gold, coding equipment, (Japanese and German) and more. The recovered items would be taken to New Orleans for cleaning, conservation, and corrosion treatment to prepare for an exhibition. Mandalay Bay Casino had offered $20 million for the exhibition. After three years in Las Vegas everything except the gold would be returned to Japan to be placed at the city of Kure in a permanent exhibition. There are no full-size Japanese WWII submarines on display anywhere in the world; however, captured Japanese midget submarines are on display at the Admiral Nimitz Museum in Fredericksburg, Texas, at the USS Bowfin Museum Submarine Museum and Park, close to Pearl Harbor, Hawaii, and at the Australian War Memorial, Canberra.

In 2000 the National Geographic Society commissioned and produced a documentary called, Submarine I-52: The Search for WWII Gold, on the I-52 and Tidwell's salvage effort.

The Japan Times, in an article dated 19 April 2005, reported that Tidwell intended to return to the site and raise the submarine in November 2005 or May 2006. However, as of 2008, Tidwell's plans have not been fulfilled.


I-55 was a Japanese C3 class attack submarine completed on 20 April 1944.

I-55 was sunk after only three months in commission.

Assigned to the defense of the Marianas, during a mission to rescue staff of the 1st Air Fleet on Tinian, she was presumably found and sunk by the USS Gilmer and USS William C. Miller on 14 July 1944, though some sources claim this sinking was actually the submarine RO-48 due to the fact that the USS Wyman and USS Reynolds also logged references to the sinking of the I-55 submarine in which Wyman claims credit for this sinking on 28 July 1944.


I-53 survived the war, but she was scuttled by the US Navy off the Gotō Islands in 1946.





The Hei-Gata Type-C submarines were also utilized as Kō-hyōteki (midget sub) or Kaiten (manned torpedo) mother ships.

A midget submarine is any submarine under 150 tons, typically operated by a crew of one or two but sometimes up to 6 or 8, with little or no on-board living accommodation. Midget submarines normally work with mother ships, from which they are launched and recovered, and which provide living accommodation for the crew and other support staff.


Ko-hyoteki class midget submarine

The Ko-hyoteki ("Type 'A' Target") class was a class of Japanese midget submarines used during World War II. They had hull numbers but no names. For simplicity, they are most often referred to by the hull number of the mother submarine. Thus, the midget carried by I-16 was known as "the I-16 midget". The midget submarine hull number began with the character "HA", but is visible only on the builder's plate inside the hull.

Fifty were built. The "A Target" name was assigned as a ruse — if their design was prematurely discovered by Japan's foes, the Japanese Navy could insist that the vessels were battle practice targets. They were also called "tubes" and other slang names.

The first two, Ha-1 and Ha-2, were used only in testing. They did not have conning towers, which were added to the later boats for stability underwater.

Ha-19 was launched by I-24 at Pearl Harbor. Most of the other fifty are unaccounted for, although three were captured in Sydney (Australia), and others in Guam, Guadalcanal, and Kiska Island, accounting for some of the other hull numbers.

The submarines were each armed with two 450 mm torpedoes in muzzle-loading tubes one above the other on the port bow. There was also a self-demolition charge which it has been suggested was large enough to enable the submarine to be used as a suicide weapon, but there is no evidence that it was ever used as one.

Each submarine had a crew of two men. A junior officer conned the boat while a petty officer manipulated valves and moved ballast to control trim and diving.

Five of these boats participated in the Pearl Harbor attack, with at least one actually making it into the harbor. Of the five used at Pearl Harbor, HA-19 was captured where it grounded on the east side of Oahu. During World War II, HA-19 was put on tour across the United States to help sell War Bonds. Now a US National Historic Landmark, HA-19 is on exhibit at the National Museum of the Pacific War.









Kaiten class manned torpedo

The Kaiten ("the turn toward heaven") was a fast torpedo modified for use as a steered suicide weapon, and used by the Imperial Japanese Navy in the final stages of World War II.

Early designs allowed for the pilot to escape after the final acceleration toward the target, although whether this could have been done successfully is doubtful. There is no record of any pilot attempting to escape or intending to do so, and this provision was dropped from later production kaitens, so that once inside, the pilot could not let himself out. In the event that an attack failed, the kaiten was fitted with a charge for self destruction.

Five models were designed, the types 1, 2, 3 and 4 based on the type 93 torpedo (24 inch oxygen/kerosene), and the type 10, based on the type 92 torpedo (21 inch electric). Types 2, 4 and 10 were manufactured in small numbers and never used. Prototypes of the type 3 may have been built, or it may have existed only as a concept.


Only the type 1, a one person model with a 3000 lb (1,360 kg) warhead, was used operationally. Almost 400 of these were built, with more than 100 of these sent on suicide missions. As well as the obvious advantage of providing guidance for the torpedo, these kaitens could be launched from a submerged submarine, unlike the unmanned type 93 torpedo which was deck launched from the surface. However they were not nearly as effective round for round as the highly successful type 93 torpedo on which they were based. Sources from the United States state the only sinkings achieved by kaiten attacks were the tanker Mississinewa on November 20, 1944, and the destroyer Underhill on July 24, 1945 (some Japanese sources give much larger numbers).

The type 2 was intended to have a crew of two, and so is often confused with the Japanese Ko-hyoteki class midget submarines used to attack Pearl Harbor and Sydney. However, the midget submarines used in these attacks were each armed with two light torpedoes in individual tubes, and were intended to return to their mother ships after firing them. All kaitens, on the other hand, had only fixed warheads, and were single mission munitions. The quality of construction also reflected this fundamental difference.

All kaitens were designed to be launched from either the deck of a surface ship or the deck of a submerged submarine. Provision was made for the crew to enter the kaiten from the submarine while submerged. Having a very limited depth capability themselves, when carried on a submarine deck the kaitens similarly restricted the diving depth of the submarine itself. This is one of several factors blamed for the very poor survival rate of submarines using them, eight submarines being lost while sinking only two enemy ships and damaging some others. A submarine carried three to six kaitens.



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NB: The above text has been collected / excerpted / edited / mangled / tangled / re-compiled / etc ... from the following online sources :

IJN - Hei-gata Type C submarine - wikipedia article #1

IJN - Type C3 submarine - wikipedia article #2

IJN - Japanese submarine I-52 (1943) - wikipedia article #3

IJN - Japanese submarine I-55 (1944) - wikipedia article #4

IJN - http://en.wikipedia.org/wiki/Midget_submarine - wikipedia article #1

IJN - Ko-hyoteki class MIDGET submarine - wikipedia article #1

IJN - Kaiten class MANNED torpedo - wikipedia article #1