Even in the 21st century the submarine remains one of the stealthiest weapons of war. Advances in sonar technology and magnetic anomaly detectors has done much to improve the chances of detecting submarines but the advantage is still very much on the side of the submariner even when he is facing another submarine. Submarines are in a much better position to detect other submarines than surface vessels as their hydrophone detectors can take advantage of underwater currents carrying the sound or sonar ping from a nearby submarine. Nevertheless it still remains one of the most difficult missions in warfare; sinking one submarine with another submarine whilst both are submerged. In the history of submarine warfare there has so far only been one occasion where a submarine successfully carried out an attack on another while both were submerged.
While the story of submarine warfare is remembered as one of surface ships hunting the elusive submarine or U-boat as it tries to sneak through naval defences to reach the highly valuable merchant ships the truth is submarines have fought one another ever since the type went to war in 1914. British submarines were heavily involved in providing a defensive screen against German submarines that tried to attack the troop ships crossing the English Channel at the outbreak of war. The Germans spotted the British submarine screen and the two sides tried to lure one another in to combat but all in vain. Nevertheless the British submarines still achieved their mission by keeping the Germans away from the vital troop ships carrying the British Army to France.
On the 18th of October 1914 the British submarine HMS E3 under the command of Lieutenant Commander George Cholmney was conducting a patrol in the North Sea off Borkum, an island off North West Germany. During the course of the day the E3 spotted a small flotilla of German destroyers and began stalking them however the destroyers had the advantage of speed and the E3 was not able to get in to a good firing position. Cholmney therefore elected to hide his submarine in a nearby bay believing the German destroyers would either return or disperse thus allowing him a second chance to engage.
Unbeknown to Cholmney the bay was already occupied. The sleek lines of U-27 under the command of Kapitänleutnant Bernd Wegener slid through the waters with its lookouts atop the coning tower scouring the horizon. They quickly spotted what they suspected to be a buoy floating by in the distance but there wasn’t supposed to be one there and on closer inspection Wegener realised that it was in fact a British submarine. He immediately ordered his crew to diving stations and he closed on the target expertly positioning his submarine between E3 and the afternoon sun in order to make spotting his periscope more difficult to see in the glare on the water.
Having pursued the E3 for nearly two hours the distance between the U-27 and the still oblivious E3 had closed to 656 yards (600m) and Wegener decided it was time to engage the enemy vessel. He dispatched two G6 torpedoes at the British submarine and after travelling for twelve seconds they struck the stern of the submarine blowing it clean off from the rest of the submarine’s forward hull. There were no survivors from HMS E3 which has the unfortunate distinction of being the first submarine to be sunk in action by another.
Throughout World War I and World War II submarine versus submarine actions were infrequent and often resembled that of the sinking of E3; one submarine spots another on the surface and fires at it. While naval Anti-Submarine Warfare (ASW) technology advanced on both sides it was the aircraft that would prove the biggest threat to submarines and remains so to this day. The thought of using submarines to hunt down other submarines while submerged however was a concept that still appeared to remain confined to the realms of fiction.
There were a number of obstacles that stood in the way of World War II submarines trying to hunt each other down in the depths of the world’s oceans. First of all detecting the other submarine was still a challenge. Hydrophone technology was still very primitive and while they could give advanced warning of a surface vessel pushing its way through the waves above, a submerged submarine made less noise and so was less detectable. The sea did more than keep a submarine hidden from view as well. Sound waves don’t travel very well in colder waters making the passive hydrophone system less effective in hearing the enemy sub. ASDIC, an early form of sonar, sent out a sonic pulse to detect an object but again low temperatures hindered its effectiveness. Unsettled water also disrupted the pulse degrading its strength but the biggest problem with ASDIC was that while it could give a direction it couldn’t give a depth.
Even if a submarine could detect another submarine engaging it in combat presented its own problems. Firstly the torpedoes themselves had to be set to a neutral buoyancy rather than their usual run depth which in World War II was just below the waterline of a ship. If this wasn’t achieved then the launched torpedoes would rise upwards rather than straight on towards the target. By World War II the first primitive targeting computers were being installed in submarines for aiming the torpedoes but these were designed for attacking surface based targets. They therefore operated in a two-dimensional capacity (forward and to the left/right of the attacking submarine) as opposed to the three-dimensions required for fighting below the surface (forward, left/right and above/below the attacking submarine).
Given all these factors it is no wonder that only once has a successful attack on a submerged submarine by another submerged submarine been carried out in military history. The story begins in the twilight of World War II and has all the hallmarks of a Tom Clancy thriller. As 1945 dawned the fate of Nazi Germany seemed sealed. The allies were now marching eastwards across western Europe and north through Italy while in the east the massive juggernaut of the Soviet Union was bearing down to complete the ever tightening noose around the neck of Hitler’s Third Reich. In the Pacific theatre the almost paper ally of Germany, Japan was in a similarly dire state but unlike Germany Japan still had distance on its side. It was clear that Japan was not going to be defeated before Germany and that the war in the Pacific would likely last another few years as only a handful of people knew of the awesomely destructive weapon the Manhattan project was developing that would ultimately bring about peace. As part of the alliance with Japan, Germany promised to supply advanced weapons and technologies to its Far East ally that would help keep the Americans at bay. This policy continued throughout the war and even in the dark days of 1945 the Germans were sending this advanced technology to Tokyo.
Naturally, intercepting these shipments became a high priority for the allies and in December 1944 British codebreakers intercepted communications between Germany and Japan of an upcoming shipment expected to leave Norway via U-boat. The overwhelming strength of allied air and naval power meant that U-boats now offered the only chance of getting through to Japan as merchant ships would almost certainly be detected and sunk. On the 5th of February 1945 U-864 slipped its moorings at the Bergen U-boat bunker in Norway under the command of Korvettenkapitän Ralf-Reimar Wolfram with its destination being Japan. The departure had been repeatedly delayed due to first a faulty snorkel and then again after the U-boat ran aground attempting to leave Kiel in Germany forcing it to Bergen for repairs. Whilst in Bergen it was again damaged this time in a visit by the Royal Air Force’s famous No.617 Squadron and their Lancasters carrying 12,000lb “Tallboy” bombs. The U-boat pen was damaged and this in turn damaged U-864 and delayed repairs further. Now however despite the fact that Germany’s situation was growing ever direr in Europe the mission, codenamed Operation: Caesar, was to go ahead.
Wolfram’s U-boat was crammed with material destined to aid Japan’s fight against the allied nations in the east. This included 61 tons of metallic mercury which was a material growing increasingly scarce in Japan and used in bomb trigger construction. Perhaps of greater concern to the allied cause were numerous boxes containing engine parts for the Junkers Jumo 004 jet engine that powered the Messerschmitt Me262 jet fighter. The intention was for Japan to reverse engineer these components in order to build their own jet fighters that could counter the devastating B-29 Superfortress raids that were bringing Japan to its knees. Other boxes contained guidance systems for the V-2 rocket again for use by the Japanese in developing their own rocket program although this was at a significantly less advanced stage than in Germany.
The U-boat also included four passengers. Tadao Yamoto was a Japanese acoustic torpedo expert who had travelled to Germany to compare notes and inspect German efforts in developing the first guided torpedoes. Toshio Nakai was an expert in the manufacture and employment of different fuel and was most likely involved in examining the fuel systems of the Me262 for use in Japan’s jet fighter project. Finally, emphasizing just how important the jet fighter project in Japan was to the Japanese, two Messerschmitt engineers were also aboard. The U-boat’s mission therefore was given the highest of priorities and conducted in the strictest secrecy.
Somewhat ironically it was this level of secrecy that betrayed the U-boat for the codebreakers at Britain’s famous Bletchley Park intelligence operation had cracked the German codes and learned of the mission. The Admiralty was immediately alerted about the U-boat and quickly went in to action to intercept it. Among the assets available was HMS Venturer, a V-class patrol submarine, under the captaincy of Lieutenant Jimmy Launders. Launders was known to have a brilliant mathematical mind that made him an ideal submarine commander and in the coming engagement this mathematical prowess would manifest itself in spectacular fashion. Venturer had already made a name for itself when it came to fighting other U-boats having sunk U-771 the previous November with torpedoes while it recharged its batteries on the surface.
Royal Navy Submarine Command, using the best information it had available to it, ordered Launders and the Venturer to patrol near the island of Fedje off Norway’s southwest coast in the belief that this was the most likely place where U-864 would be transiting in its attempt to break out. Venturer was one of an increasing number of British submarines that had been fitted with its own ASDIC system but the calculative Launders reasoned quite correctly that if Venturer went about sending out ASDIC pings to hunt for the U-864 it would alert the Germans to his presence and even invite attack. Venturer therefore stalked the waters around the island silently listening for the sound of a U-boat with its hydrophone equipment. Unfortunately for Venturer U-864 had already passed the island and had apparently escaped but as often is the case in war luck was about to play its part.
Wolfram was having problems with U-864’s engines. While they appeared to be functioning properly they were generating a great amount of noise indicating there was a problem deep inside the engine block. Afraid of breaking down hundreds of miles from a friendly port Wolfram elected to reverse his course and cancel the mission yet again. It must have been extremely frustrating for Wolfram and his men who unknown to them were now sailing back towards Venturer’s hunting ground.
Given his calculating mind Launders had begun to reason that they had indeed missed U-864 as he continued his patrol on the morning of February 9th 1945. Then suddenly he was informed by his hydrophone operator that he was detecting a sound in the distance. When asked what the sound was the hydrophone operator responded by saying that it sounded like a fishing boat’s diesel engine had started up. Launders suspected that it was more than a simple fishing boat’s engine. He reasoned that it was quite likely to be a submarine surfacing to charge its batteries since the noise seemed to appear out of nowhere. He therefore ordered his submarine to head for the sound of the diesel engine.
As they closed on the source of the noise the officer of the watch aboard Venturer raised the periscope and reported sighting another periscope cutting through the water. In actual fact he had spotted U-864’s snorkel which allowed the U-boat to run its diesel engines while submerged by feeding in outside air and ejecting the exhaust fumes. Snorkels were a relatively new invention and were only on German U-boats at this point hence the officer’s mistake. Launders now formulated a plan of attack. While the noisy diesel engines aboard U-864 were running he knew that the U-boat’s own hydrophone system would have a difficult time detecting his vessel and so the element of surprise was still on his side. Launders believed that the U-boat would have to surface soon not realizing what the snorkel was and the advantage it offered to the U-boat. He planned to stalk the U-boat until it surfaced and then attack it with torpedoes as it had done when attacking U-771 in the previous November.
For several hours Venturer followed U-864 which was zig-zagging from side to side as it made its way back to Norway; a common tactic to reduce an enemy submarine’s ability to acquire a firing solution with a high chance of scoring a hit. Time was quickly running out for Launders however as his own engine room reported that Venturer’s batteries were being drained rapidly by the pursuit and she would have to surface to charge them before long. Realizing that U-864 was not about to surface anytime soon Launders was faced with a choice; attack while the U-boat was submerged or break off the pursuit.
Launders’ mind began running numbers as he contemplated the chances of a successful engagement. He had a rough estimate of how deep the U-boat was thanks to the fact he could see its periscope (snorkel) but that didn’t guarantee accuracy. Launders reasoned that his best chance of success was to ripple fire all four of his forward torpedoes in to a kill-zone around the U-boat’s estimated position. Each torpedo would be fired independently at 17;5 second intervals and each successive torpedo would be directed differently assuming that if the first torpedo missed then the U-864 crew would be alerted to Venturer’s attack and take evasive action. Launders was calculating the first three dimensional submarine attack in history.
He had precious little battery life left and so he moved his submarine in to the most optimal attack position he could attain. Launders and his men knew their chances of success were low but they pressed on anyway determined, in that defiant spirit of the submarine service, to give it their best shot. The first torpedo left its tube and began its run while Launders counted down on his stopwatch towards the launching of the second torpedo. The frantic sounding whirl of the torpedo did indeed alert the crew of U-864 which quickly began efforts to take evasive action but the large U-boat was no ballerina and in order to submerge further to the protection of the deep the diesel engines had to be shut down and the electric motors started up all of which took time. Nevertheless the first torpedo was off target and missed as did the second.
After 53 seconds the third torpedo raced out of its tube and began its run. The fourth and final torpedo left the submarine 17.5 seconds later and with none left to fire Launders ordered his submarine to go deep to avoid counter attack. The submarine began a steep dive down in to the depths below as Launders watched the seconds tick by. He knew that if the third torpedo had found the target then they would have heard the explosion by now and so he assumed that it had missed. Everything now lay on the final torpedo.
There was a deep booming sound in the ocean outside. The explosion sent a shockwave familiar to the crew of a successful submarine as that of an enemy vessel exploding. Through the hydrophones Launders could hear the sound of popping rivets and breaking bulkheads confirming that he had hit the target. U-864, in taking evasive action to avoid the third torpedo had actually turned in to the path of the fourth just as Launders had predicted and now both the U-boat and its precious cargo were being sent to the ocean floor below. It remains the most unique submarine action in history.