The German Submarine U-864

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U-864 was a German submarine active during World War II. U-864 was a Type IX U-boat would be part of the Nazi Germany’s Kriegsmarine.

Type IXD2 submarines, of which U-864 is one, are much larger than the original Type IX submarines. This particular model had a displacement of around 1610 tons at the surface and 1799 tons under water. This submarine had a length of 287 feet, a hull length of 224 feet, a height of 33 feet, a draught of 17 feet and a beam of 24 feet. It was equipped with a two MAN M (V 40/46 supercharged four stroke, nine cylinder diesel engine along with two MWMRS34.5S six cylinder four stroke diesel engine for cruising. both these engines together produce a power of 9000 metric hp while at the surface. For underwater movement, the U-864 had two Siemens-Schuckert 2 GU 345/34 double acting electric motors, which produced a total of 1000 hp. She had two 6 feet propellers and two shafts, which allowed her to plunge into depths of about 660 feet.

The submarine had a speed of 20.8 knots at the surface and a speed of 6.9 knots when submerged. She could travel for 121 nautical miles at the speed of 2 knots when she was underwater. However, at the surface she could travel at 12750 miles at the speed of 10 knots. U-864 had tubes for six torpedoes. Four of these were at the bow and the remaining two were at the stern. She carried twenty-four torpedoes, a 10.5 cm SK C/32 naval gun with 150 rounds, and a 3.7 cm naval gun with 2575 rounds and also 2 cm anti-plane guns with 8100 rounds. The boat had a crew capacity of fifty-five.

U-864 was commanded by Korvettenkapitän Ralf-Reimar Wolfram. During her training period she served with the 4th U-boat flotilla. After October 31st 1944, she was sent to serve under the 33rd U-boat flotilla.

The U-boat’s final mission was to transport equipment to Japan. This mission was codenamed Operation Caesar. She was carrying 61 tons of mercury in steel flasks. Theses flasks were stored in the keel. Japan had bought nearly 1400 tons of mercury from the Italians between 1942 and 1943. This mercury was used to create explosives, mainly as primers. This is why this mission was made top priority.

At that time, there were some rumors that U-864 could be carrying uranium oxide like her sister U-boat, U-234. U-234 had surrendered to the US Navy on May 15th 1945. However, Det Norske Veritas (DNV) which is a risk assessment company founded in Norway arrived at the conclusion that there was no uranium oxide on board the U-864 when she had departed the port at Bergen. This information was further corroborated when the Norwegian Coastal Administration investigated the submarine. According to the cargo list, the U boat was carrying the designs and plans for a German jet fighter and various other supplies for Japan to use. Her passenger list showed Tadao Yamoto, the Japanese torpedo expert, and Toshio Nakai the Japanese fuel expert were on board along with Messerschmitt engineers Riclef Schomerus and Rolf von Chlingensperg.

Operation Caesar was supposedly a secret mission by the Germans to supply their ally, Japan with some of their advanced technology so that Japan could make a comeback in the war. This was a complete failure due to the engagement of the only known submerged submarine war in history. Never before, or after, had a submerged submarine been able to attack and destroy another one. Most submarine attacks were made on ships and at the most on submarines that were at the surface.

U-864 arrived at Horten in Norway on December 9th 1944, four days after she left the port at Kiel. Before leaving Kiel, she was fitted with a snorkel mast. All Schnorkel trainings and trials were conducted at Horten. This is why U-864 had to stop there before proceeding to Bergen. A snorkel mast was essential and the problem would have to be fixed before she began her mission to Japan.

On the way to Bergen, the U boat was grounded and had to head to Farsund for repairs. This delayed her journey to Bergen. She finally reached Bergen on January 5th 1945. While U-864 was moored at the harbor along with the other U boats, there was an attack on the harbor by one Mosquito bomber and thirty-two Royal Air Force Lancaster bombers. A Tallboy bomb managed to penetrate the roof of a bunker causing major damage on the inside and left one of the pens for the boats unusable for the rest of the war. U-864 suffered from some minor damage during the attack.

Once the repairs were completed on the U-864, she underwent a few trial runs at Bergen. The British submarine, the HMS Venturer was out on her eleventh patrol from the base at Lerwick in the Shetland Islands. She was sent along the coast from Lerwick to Fedje, which is just north of Bergen. It was during this mission that the British code breakers from Bletchley Park intercepted the communication between Germany and Tokyo concerning U-864’s mission to Japan. Once the British realized that this submarine was on its way to give supplies to Japan, they decided that they had to intercept it at any cost. Hence, the HMS Venturer was sent to intercept the U boat.

On February 6th U-864 had passed through Fedje without being detected. However, luck wasn’t on her side. Just as she crossed Fedje, one of her engines misfired. So she was ordered back to Bergen for repairs before she continued with her mission. An order stated that she would be provided with a new escort of February 10th. U-864 turned around and made her way back to Bergen. However, on February 9th, before she could make it back to Bergen, Venturer had heard the sound of the engine and spotted her periscope. The commander of the Venturer had decided not to use ASDIC since it would reveal his presence.

Neither crew had been trained for a situation like this. The commander of the Venturer waited nearly forty-five minutes before asking his men to get to their stations in a hope that U-864 would rise to the surface. Once the crew of U-864 realized that they were being chased by a British submarine, they started using zigzag maneuvers to try to evade them. Evading the British submarine was the only thing they could do because their escort was yet to arrive and would not arrive anytime soon. While the Venturer had only eight torpedoes, the U-864 has twenty-two but since she was busy trying to evade the British submarine she didn’t initiate the attack.  After three hours of being chased the Venturer, the crew heard the sounds of torpedoes being launched. U-864 was already submerged but dived deeper once she realized that torpedoes were being launched. She managed to avoid three of the torpedoes but she unwittingly steered directly into the path of the fourth one while trying to escape the third torpedo. In doing so, she exploded into two parts and sank to the bottom, crew and all. The torpedo ripped through the captain’s bridge and conning tower, but the remaining parts of the submarine are intact. She came to rest on the seabed, 500 feet from the surface and 2.3 miles away from Fedje. It was Harry Plummer who fired those torpedoes. He was later interviewed and he recounts his experience of that fatal day, “It was such a relief that you got rid of… And the next minute I realized it was another submarine and more submariners were killed. We realized it was nothing to be happy about.”

Beyond this, nobody knows what other secrets the U-864 holds. With its toxic cargo, the U-864 has found a permanent tomb underwater for the 73 sailors on board. These mercury flasks prevent anybody from knowing what other top-secret cargo the U boat was carrying.

Many historians believe that Operation Caesar was Hitler’s last desperate attempt in trying to reverse the war. This is why there was such an interest in finding the cargo of the submarine, U-864. If this mission had turned out successful then the war might have had a very different ending or at the very least, lasted longer than it did. The British were extremely lucky to have managed to destroy one of the operations that might have changed the course of the war.

The wreck of the U-864 was found by a group of fishermen who then notified the Royal Norwegian Navy. The KNM Tyr, a minesweeper found the wreck in March 2003.  The exploded sections of the submarine were found scattered over the area.  An operated underwater that could be controlled remotely was used to locate these pieces in 2005. The mercury stored in flasks in this submarine has eroded and the mercury is slowing leaking into the environment. This was contaminating the sea flora and fauna. As many as 1857 steel flasks were discovered in the keel of the submarine. This discharge of mercury could lead to a possible mercury-poisoning situation in the coastal towns surrounding the wreckage. Nearly 4 kilograms of mercury gets released into the water surrounding the wreck every year. This mercury ends up in the plants and fish that live in the waters. There are high levels of this mercury in the crab, torsk and cod around the wreck. Initial studies showed that the mercury levels in the silt surrounding the wreck were at such high levels that if they were absorbed by the fish it could easily affect humans. The Norwegian government has banned all fishing and boating near the wreck. Using robotic vehicles, one of the steel flasks from the wreck was recovered and studied by several environmentalists. The flasks were originally 5 mm thick but because of continuous water erosion and corrosion, they have become just 1 mm in thickness.

The presence of the mercury bottles and torpedoes on board the U-864 make it difficult to attempt the lifting of the submarine. It would be extremely dangerous to attempt to lift the wreck. The Norwegian Coastal Administration, after three years of study has proposed that the wreck be given an underwater burial. They suggested that the submarine, or what remains of it, be buried nearly 40 feet below the seabed over which there will be a layer of concrete or gravel. The concrete and gravel is to prevent the erosion of the sand by the water. This is the only possible long-term solution to this problem of environmental pollution. This method has been used successfully in various other mercury-contaminated places. However, the locals aren’t happy with the burial of the wreck. They worry that the burial and concrete layer may not be foolproof and that the mercury will still leak.

On November 11th 2008, the Norwegian Coastal Administration decided to salvage the submarine along with its cargo. They gave out the contract for the salvage to Mammoet Salvage BV. This company was known for the salvage of Kursk, a Russian nuclear submarine in 2001. This company proposed to raise the wreck without using humans. They devised a safe and innovative way that involved the use of deep-sea robots to raise the wreck. This method would satisfy all the environmental restrictions and requirements put forth. The mission would a fully remote controlled operation that would remove the source of the pollution that is the mercury without any human coming in contact with the mercury. The Norwegian government approved of the proposal put forth by Mammoet on January 29th 2009 and the salvage process was supposed to begin in 2010. This salvage was supposed to cost approximately one billion kroner. However, the operation was put on hold because the government wanted more studies performed.

World War 2: A Submerged Submarine Sank Another Submerged Submarine


Forschungsmitarbeiter Mitch Williamson is a technical writer with an interest in military and naval affairs. He has published articles in Cross & Cockade International and Wartime magazines. He was research associate for the Bio-history Cross in the Sky, a book about Charles ‘Moth’ Eaton’s career, in collaboration with the flier’s son, Dr Charles S. Eaton. He also assisted in picture research for John Burton’s Fortnight of Infamy. Mitch is now publishing on the WWW various specialist websites combined with custom website design work. He enjoys working and supporting his local C3 Church. “Curate and Compile“
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