The Vanished Golden Submarine’s Final Journey and Fate

19. The Conundrum of Cooperation

Axis powers 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 the European and the Asia-Pacific theaters of operation, and enemy navies dominated the sea lanes between the Germans and Japanese. 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.

18. The Two Way Trade Between Germany and Japan

By the spring of 1944, both Japan and Germany were in dire straits. The Axis partners were on the defensive as Allied forces steadily advanced upon and steadily shrank their empires. Simultaneously, enemy aerial forces – and in Japan’s case naval forces as well – cut off their access to desperately needed materials and reduced their factories to rubble. The Japanese desperately needed advanced German technology and instruments, while the Germans were desperate for any exchange of information or materials with the Japanese. So a precarious two-way trade was conducted between the two countries, via the only practical means still left to them: via submarines.

17. Cooperation Over Long Distances

In December, 1941, an amendment to the Tripartite Pact between Germany, Italy, and Japan was added to include a military agreement between the Axis partners. Part of the amendment sought to establish trade routes to exchange vital supplies, plus technological expertise and technical experts. By then, Germany had invaded the Soviet Union, so land trade and exchange between Japan and her European partners via the USSR was no longer an option. So the amendment called for exchanges via aerial and sea routes. The era’s airplanes could not reliably handle aerial routes that avoided Soviet airspace, so trade and exchange via sea was the only option left.

16. The Shift to Underwater Trade

The sea route between Germany and Japan was long and hazardous. It stretched from Europe via the Atlantic, around Africa and thence into and across the Indian Ocean, and finally to the Pacific. Despite that, in a twelve-month period from late 1941 to late 1942, twelve surface blockade runners managed to complete the journey from the Far East and deliver more than 60,000 tons of supplies to German-occupied France. By late 1942, however, a combination of British intercepts of Japanese communications that led to increased interception of blockade runners, coupled with mining the Bay of Biscay, cut deeply into the trade between the Axis partners. In 1943, the Germans received only a third of the supplies that had reached them from the Far East the previous year. So a decision was made to shift the trade from surface blockade running ships, to underwater submarines.

15. Technology in Exchange for Raw Materials

Japan was desperate for German technology, while Germany was desperate for raw materials. However, Allied control of the waters in between eliminated bulk exchanges via surface transports. During World War I, 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.

14. The WWII Revival of a WWI Trick

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. Designed and manufactured by the Mitsubishi Corporation, the Type C3s measured over 350 feet in length and over 30 feet in the beam, and had crews of up to 94 men. They had a cruising range of over 20,000 nautical miles, and could do so at a long cruising range speed of 12 knots. That made the Type C3s well suited for long distance trade and intelligence missions between Germany and Japan.

13. The Yanagi Missions

The Japanese had initially planned to build twenty of the Type C3 underwater behemoths. However, 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. As to the Germans, they also sent several U-boats on hazardous missions to Japan, although they were not part of the Yanagi scheme.

12. The Golden Submarine

The Imperial Japanese Navy’s I-52 was laid down in March, 1942, and was commissioned in December, 1943. Code named Momi, or “fir tree”, she 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.

11. The Long Journey of the I-52

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^th, 1944.

10. A Valuable Cargo

In her cargo hold, the I-52 carried materiel highly sought after by Nazi Germany. It included 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.

9. The German Technology Awaiting the Japanese Golden Submarine

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.

8. What Could Have Been: Japanese Snorkel-Equipped Submarines

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, using the diesel engines underwater would have suffocated the crew. With a snorkel, however, diesel engines could be used underwater. Thus, snorkel-equipped submarines would no longer have to rely 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.

7. A Japanese Dirty Bomb?

More intriguingly, the cargo for the I-52’s 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. Such byproducts 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.

6. The American Tracking of the I-52’s Journey

Unbeknownst to either the Germans or Japanese, Allied code breakers 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^th, 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^nd. The I-52 acknowledged receipt of the message, fatally including her position in the reply.

5. Sending a Task Group After the Golden Submarine

American intelligence intercepted the exchange between the I-52 and the Japanese naval attache in Berlin, and sent out a submarine hunter-killer group. 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, after 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.

4. A Mid-Atlantic Meeting Between German and Japanese Submarines

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 its hunt.

3. Finding the I-52

At around 10PM, June 23^rd, the Bogue launched Grumman TBF Avenger torpedo bombers to try and find the enemy submarines. The U-530 slipped away undetected, but at 11:40PM, an Avenger piloted by Lieutenant Commander Jesse D. Taylor got a surface contact on its radar, about ten 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.

2. The End of the Golden Submarine

At about 11:45PM, Taylor dropped two depth bombs, set to explode at 25 feet. 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 other 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.

1.     Rediscovering the I-52 Half a Century Later

Five decades later, Paul Tidwell found the Golden Submarine’s remains in a debris field three miles beneath the Atlantic. The I-52 was resting mostly upright, with her conning tower and hull number still visible. Plans to raise the submarine were objected to by the Japanese government, which considered the wreck site a grave. Tidwell eventually worked out an agreement that allowed 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.

_________________

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

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

History Collection – Agent 50: The Heroic Spy Who Saved Hundreds From Japanese Clutches in World War II

Nauticos – I-52

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