Researchers Used Secret Methods to Locate this Mysterious Japanese Submarine Lost in WWII

Khalid Elhassan - September 1, 2019

During the Cold War, advanced deep water detection was almost an exclusively military preserve. That began to change in the early 1990s, when Paul R. Tidwell, a maritime researcher, used once highly secret military methods and gear to locate a mysterious Japanese submarine lost in the Atlantic during World War II.

In late 1994, Tidwell found the wreck of the Imperial Japanese Navy I-52, about three miles deep. It was an unusual vessel, not least because its final resting place in the Atlantic was thousands of miles away from Japan’s area of operations in Asia and the Pacific. The I-52 was also one of the biggest submarines of WWII. Even more significantly, when it sank, it was carrying more than two tons of gold, valued at about $95 million (USD) in 2019.

The Imperial Japanese Navy I-52

Germany and Japan, while formally allies in WWII, were more like co-belligerents who happened to be fighting separate wars against some of the same opponents at the same time. Vast distances separated Europe and the Asia-Pacific theaters of operation, and enemy navies dominated the sea lanes between Germany and Japan. Those factors made significant coordination, such as that between the Western Allies and the USSR, let alone that between the US and Britain, impractical. However, there was still some room for cooperation.

Japan was desperate for German technology, while Germany was desperate for raw materials, but Allied control of the waters in between eliminated bulk exchanges via surface transports. During WWI, while America was still neutral and selling goods and armaments to both sides, the Germans had partially gotten around the Entente’s dominance of the Atlantic by sending cargo submarines to the US. There, they were laden with rare and high-value goods, before returning to Germany.

During WWII, the Japanese took a page from Germany’s WWI playbook, and built large, cargo-carrying submarines. Designated the Type C3, Junsen Hei-gata Kai Sensuikan (“Cruiser Submarine Type C Modified”), and built in 1943 to 1944, these submarines were among the largest ever built to date, and among the most advanced underwater vessels of the war. Measuring over 350 feet in length and over 30 feet in the beam, the Type C3s had a cruising range of over 20,000 nautical miles. That made them well-suited for long-distance trade and intelligence missions between Germany and Japan.

The Japanese had initially planned to build twenty of these underwater behemoths, but as things turned out, they ended up building only three, with the I-52 being the first of the trio to enter operational service. Throughout the entire war, the Type C3s only carried out six long-distance missions known as Yanagi (“exchange”) between the Axis partners. Of the three cargo submarines, two were lost in action during the conflict, and only one survived the war.

The I-52 was laid down in March of 1942, and was commissioned in December 1943. Code named Momi, or “fir tree”, became more popularly known as the Golden Submarine because of her cargo when she went down. Measuring 356 feet long by 31 feet wide, the I-52 was powered by two electric diesel motors that gave her a 17.7-knot speed while surfaced and allowed her to do 6.5 knots underwater on battery power. She had a cruising range of 21,000 nautical miles at 16 knots and was depth tested for 328 feet. Her armament included six torpedo tubes, two 140 mm naval guns, and a pair of 25 mm antiaircraft guns. However, fighting was not her primary mission: she was built to carry cargo, of which she could fit 300 tons in her hold.

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The Mission to Lorient

On March 10^th, 1944, the I-52 left Kure naval base in Japan on her maiden mission. Captained by Commander Uno Kameo and crewed by 94 officers and men, the vessel had a long journey ahead of her, most of it through hostile waters. From the Sea of Japan, she was to head to the East China then South China seas. After a stop in Singapore, the I-52 was to cross the Bay of Bengal, traverse the Indian Ocean, round the Cape of Good Hope and enter the Atlantic. Then she would traverse most of the length of that ocean, before finally entering the Bay of Biscay and docking in the Nazi-controlled French port of Lorient. Her estimated date of arrival was June 6, 1944.

In her cargo hold, the I-52 carried 11 tons of tungsten, almost 10 tons of molybdenum, 3 tons of opium, and 54 kilograms of pure caffeine. She also carried 146 bars of gold, weighing 2.2 tons, intended as payment for German optical technology. In Singapore, she also picked up 3.3 tons of quinine, 60 tons of raw rubber, and 120 tons of tin. She also carried 14 passengers, mostly Japanese technicians, sent to study advanced German torpedo boat engine and antiaircraft gun technologies.

Awaiting the I-52 in Lorient, to carry back home to Japan, were about 40 tons of advanced Nazi technology, plus assorted secret documents, drawings, and schematics. The cargo for the return voyage included German radar equipment, vacuum tubes, optical glass, bombsights, chemicals, a Jumo 213-A engine used in the FW-190D fighter, and T5 acoustic torpedoes that could home in on the sound of ship propellers.

While docked, the I-52 was to also get fitted out with the latest in underwater technology: a snorkel. That device, a revolutionary advancement at the time, allowed submarines to operate underwater indefinitely while using their diesel engines (before, doing that underwater would have suffocated the crew), instead of relying solely on batteries of limited duration. The Japanese intended to reproduce the German snorkel when the I-52 got back, and to reequip their entire submarine fleet with the device.

More intriguingly, the cargo for the return trip included 1760 pounds of uranium oxide. That amount of unenriched uranium oxide would not have been enough for an atomic bomb – assuming the Japanese knew how to build one, which they did not. However, the Japanese could have used that material to create poisonous fission byproducts, that could have then been employed in radiological weapons like “dirty bombs”, for use against the US. Fortunately for the US, and unfortunately for the I-52, the Allies were tipped off about the Japanese submarine’s mission.

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The Fate of the I-52

Unbeknownst to either the Germans or Japanese, Allied codebreakers had cracked both the Axis partners’ secret communications. They did that so thoroughly that the Allies were often able to intercept, decode, and read Axis secret messages as fast as, or even faster than, their intended recipients. As a result, American intelligence had been decoding the I-52’s traffic signals ever since she had left Kure, and was able to track her throughout her long voyage. On June 6, 1944, the Japanese naval attache in Berlin signaled the submarine that the Allies had landed in France, and advised her to make plans to head for German-occupied Norway, instead. En route, she was to meet up with a German submarine, the U-530, on June 22. The I-52 acknowledged receipt of the message, fatally including her position in the reply.

American intelligence intercepted that exchange and began vectoring a submarine hunter-killer group to find the I-52. Centered around an American escort carrier, the USS Bogue, accompanied by five destroyers, the task group was en route from the US to Europe, when it was tasked with a new mission. On June 15^th, following a brief stop in Casablanca, the Bogue group sailed out to begin its hunt. It was a highly successful team of submarine killers, that had sunk a Japanese submarine just a month earlier, on May 13^th. Between February 1943 and July 1945, the Bogue team would send 13 German and Japanese submarines to the bottom of the sea.

As directed, the I-52 met up with the German U-530 on the night of June 22^nd, about 850 miles west of the Cape Verde Islands. The U-boat topped off the Japanese submarine’s fuel tanks, furnished her with an Enigma coding machine, plus a radar detector, two radar operators, and a German liaison officer to help get her through the Bay of Biscay. The following evening, June 23^rd, the Bogue submarine killer group reached the area of the meeting, and began hunting.

At around 10 PM, June 23, the Bogue launched Grumman TBF Avenger torpedo bombers to try and find the enemy submarines. The U-530 slipped away undetected, but at 11:40 PM, an Avenger piloted by Lieutenant Commander Jesse D. Taylor got a surface contact on its radar, about 10 miles away. Taylor homed in on the radar blip, got there within minutes, then dropped flares to illuminate the area. By their glare, the surfaced I-52 became visible to the naked eye. Taylor immediately dropped sonobuoys – a type of underwater microphone that picks up propeller sounds and transmits them to an airplane – then began his attack.

At about 11:45 PM, Taylor dropped two depth bombs, set to explode at 25 feet, and both he and his plane’s gunner saw one bomb explode almost directly on the starboard or right side of the I-52, and another explode about 75 feet away. Two minutes later, Taylor followed that up with an acoustic torpedo, and shortly thereafter, the sonobuoys detected the sounds of an explosion, followed by those of a hull breaking up. Per Taylor, it was: “a crackling and crunching noise … the sounds of a tin can being crushed“. The next day, the area was covered by an oil slick of about 15 square miles. There was also considerable evidence of the submarine’s demise, such as blocks of floating raw rubber, as well as bits of flesh, including a foot in a sandal with Japanese characters. The I-52’s months-long journey had come to an end.

Half a century later, Paul Tidwell found her remains in a debris field three miles beneath the Atlantic, resting mostly upright, with her conning tower and hull number still visible. Plans to raise the I-52 were objected to by the Japanese government, which considered the wreck site a grave. Tidwell eventually worked out an agreement with the Japanese government, allowing him to recover the submarine’s cargo, put it on display, then return all artifacts – except the gold – to Japan. In the end, however, the recovery efforts only managed to locate a single box of opium, but no gold.

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Where Did We Find This Stuff? Some Sources and Further Reading

Combined Fleet – Sensuikan! IJN Submarine I-52: Tabular Record of Movement

Naval Historical Society of Australia – I-52, Japan’s Golden Submarine, Sunk in the Atlantic in 1944

New York Times, July 18^th, 1995 – Lost Japanese Submarine With 2 Tons of Axis Gold Found on Floor of Atlantic

Pacific Wrecks – I-52 Japanese Submarine

Wikipedia – Japanese Submarine I-52 (1942)

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