The HMS Venturer and the U-864
The HMS Venturer sinking the U-864 on February 9, 1945 remains to this day the only intentional sinking of a submarine by another submarine when both were at periscope depth. The U-864 was a U-boat designed by the Germans for ocean-going voyages that were long a long way from home ports. In February of 1945 the submarine was a on a mission code-named Operation Caesar to give high sensitive technology to the Empire of Japan. The technology included jet engines, missile guidance systems and 65 tons of mercury.
The British had learned about Operation Caesar due to their ability to crack the Enigma code. The British wanted to stop the Germans from giving the Japanese anything that might prolong the war and therefore wanted to stop the U-864. The Royal Navy submarine command dispatched the HMS Venturer to destroy the U-864 before it was able to deliver its cargo to Japan. At the time, Lieutenant Jimmy Landers was in control of the Venturer and was given little more than the estimated whereabouts of the U-864 and the orders to bring down the sub.
Landers decided to turn off the sub’s ASDIC in order to prevent the ping from being overheard by the U-864. The submarine relied on its hydrophone to pinpoint where the U-864 was. The plan was successful as the Venturer’s hydrophone operator was able to hear the diesel engines of the U-boat as it passed the Venturer’s location. The Germans did not have sonar at the time and their hydrophone was unable to hear the electric motors of the Venturer over the sound of its own diesel engines.
The crew of the Venturer knew that their target was close but after tracking the U-boat for several hours it became clear that it was not going to surface. Never before had a firing solution been computed in four dimensions – time, distance, bearing and target depth, despite it being possible. The crew of the HMS Venturer was running out of battery life and knew they had to make an attempt. The made the calculations and made assumptions about the defensive maneuvers of the U-boat and fired all torpedoes out of four bow tubes. The fourth torpedo struck the target, puncturing the pressure hull and instantly imploding the U-boat.