Operation Caesar was the codename for a secret mission to transport scientists from Nazi Germany to Japan. Operation Caesar required U-864 to sail from Kiel in North Germany via the Cape of Good Hope to Penang in Malaysia. The start date for Operation Caesar was December 5th 1944.


The cargo of U-864 was highly secret and few on board knew what their mission was. The captain for such an important voyage, Ralf Wolfram, was relatively inexperienced and would have seemed a curious choice as captain for such a vital task. However, such were the losses of U-boats by the end of 1944, that no experienced U-boat captain was available and the Kriegsmarine had to use someone with lesser time at sea.


U-864 was no ordinary U-boat. She was a long distance 9D2-class diesel powered submarine capable of sailing many miles without support. This was significant, as the cargo being carried by the submarine was highly important. The Japanese, allies of Germany since December 1941, wanted access to Germany’s jet engine know-how and U-864 was carrying highly secret jet engines from Messerschmitt, BMW and Junkers. Scientists from both German and Japan planned to work on the engines once U-864 had docked in Penang. 


Such a long journey was fraught with danger as the Allies had full control of the North Sea, the eastern Atlantic and the Indian Ocean. The scheduled journey of U-864 was expected to take months and during all this time it was expected that she would avoid detection. By Xmas 1944, both Germany and Japan were on the verge of defeat and their naval power was simply not capable of matching the firepower of the Allies – both in the European and Asia theatres of war. Probably the most heavily patrolled part of U-864’s journey was the North Sea. The British had a fleet of submarines based at Scapa Flow and the sea between Scotland and Norway was a major part of their patrols.


U-864 left Kiel with few problems. However, the journey to the North Sea was highly dangerous, as it required venturing near to the Norwegian coastline. For an experienced U-boat captain it would have been a major task to get into open waters but for an inexperienced captain the pressures were far greater. By hugging the coastline of Norway, Wolfram hoped to use the heavy German fortifications to give him support on the surface if it was needed. He also knew that any British submariner would have been very wary about getting too close to the shore because of these defences.


The journey started well. However, just as the submarine passed Farsund, the crew heard and felt a sizeable bump – U-864 had grounded. The captain checked that no damage had been done to the hull but the submarine’s engineer reported that an engine had lost all power. The captain had no choice but to head for a dry dock for repairs. The nearest was in Bergen, Norway. Here the crew had to wait for the repairs to be completed. The delay was annoying, as it would put extra days onto what was already a marathon journey. There was a further delay when Lancaster bombers bombed the submarines pens and there was more damage done to U-864, which required repairs. 


What the crew did not know was that the delay was to be fatal as it allowed a British submarine to get to the area where U-864 was – once she took to the seas again – to hunt her down. No one in Germany, and therefore no one on U-864, knew that the British knew all about the journey and the delay. Staff at Bletchley Park had monitored and cracked all the coded messages that had been sent to U-864 and from the submarine back to its base in Kiel.


The British submarine ‘HMS Venturer’ was sent to the area to find U-864. ‘Venturer’ was captained by Lieutenant (later Commander) James ‘Jimmy’ Launders. He was a highly regarded submariner and ‘Venturer’ already had 13 kills to its name. One of the crew, Harry Plummer, was later to say:


“He knew his job. He got on with his job. He was a good commander. We’d have gone to the end of the Earth for him, he was that good.”


The delay due to engine malfunction gave the ‘Venturer’ just that bit more time to get to the area the British knew U-864 would sail to – Helliso. The last message ever received by U-864 was for the submarine to meet up with a rendezvous ship at Helliso. ‘HMS Venturer’ attempted to predict the route U-864 would take to this rendezvous. A combination of luck and skill had fatal consequences for all on board U-864.


However, being in the same area was one thing. Finding a submarine that was frequently underwater was quite another issue. At that time, no hunter killer submarines existed – submarines that had the specific task of hunting out submersed enemy submarines. The ‘Venturer’ needed both luck and a considerable amount of skill. The luck came on February 8th 1945 when an engine in U-864 blew and made a considerable amount of noise while the crew attempted to repair it. Underwater, such noise travelled miles and was a key giveaway to any nearby British submarine. It was picked up by ‘Venturer’ on February 9th.


Another piece of good luck came when a routine periscope patrol by ‘Venturer’ saw an upped periscope in the distance. Wolfram had used his periscope to look out for his rendezvous ship. Launders assumed that it could only be U-864’s. He also had to conclude that they had not seen him though this was an assumption that he had no way of proving. If he had seen U-864’s periscope, they may well have seen his. As it was, the ‘Venturer’ was lucky. U-864 had no knowledge that ‘Venturer’ was tailing her. The ‘Venturer’ did not use ASDIC as its use may well warned U-864 of its presence. Instead, the ‘Venturer’ used its hydrophones to listen for propellers.  The ‘Venturer’ realised that what it could hear was not the engines of fishing boats but of a submarine engaging in avoidance tactics.


Using information from his ASDIC officer ,Launders noted that U-864 was sailing in a zigzag pattern – not unusual for a submarine attempting to avoid any form of detection. Using the measurements given to him, the captain tried to predict where U-864 would be at certain times.


Using these predicted measurements, four Mark 8 torpedoes were launched at 12.12 at 17.5-second intervals to cover as much of a spread as was possible. Knowing when each torpedo was due to hit U-864, it is known that it was the fourth torpedo that hit the German submarine at 12.13 and sank it, killing all 73 on board. Hydrophones picked up the sound of what was clearly a submarine sinking and at 12.14 Launders declared “a hit”. This was the first occasion that while in combat a submersed submarine had sunk another submersed submarine.


Many years later an expedition for U-864 found the U-boat in two parts just off the coast of Norway. Its crew and passengers are still entombed. However, what is now known is that U-864 was also carrying something more than just jet engines for the Japanese. The submarine was carrying a considerable number of containers of mercury – used in the production of weapons. 1857 containers held 60 tons of mercury. Many of these were not broken as U-864 sank and recovery of as many as possible is considered a priority if there is not to be an ecological disaster off the coast of Norway. While U-864 may not have delivered its cargo to the Japanese in the last few months of World War Two, its legacy has lasted much longer than anyone planning its journey from Kiel to Japan could ever have expected.        


March 2011