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In the movie U-571 (IMDB) there's a scene where two U-boats fire torpedoes at each other, at close range, while both submerged.

I always imagined U-boats would fight one another while on the surface, with their deck guns. Use of torpedoes underwater adds the problem of the third dimension, thus hitting an underwater target would be very improbable and a waste of ammunition.

I am sure modern submarines have no problem firing at each other in 3D space, but I'm not convinced that the scenario I describe has never happened with their WW2 predecessors, however unlikely.

Are there any references to this tactic?

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marked as duplicate by o0'., Tom Au, Mark C. Wallace, Kobunite, Pieter Geerkens Apr 17 '14 at 23:36

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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There is a famous book/movie, "Run Silent, Run Deep", which involves a submarine duel based loosely on real events.

Submarines can and will hunt and kill each other. In WWII torpedoes did not have active seekers, but relied on contact fusing, which means you would have to set the depth of the torpedo and make a direct hit. This would be very difficult to do because the other sub is a much smaller target than a ship. Nevertheless, in specialized scenarios it is possible. For example, if you are directly following an enemy sub and right behind him, you can load up and just wait for him to turn, then fire, he is 95% dead, even with no active homing.

The main reason this almost never happened in WW2 is because in that war submarines neither were designed to attack each other, or had that as their mission. They were designed as ship killers only, and that is what they did. Run Silent, Run Deep only occurred because the Japanese had specially tasked one of their subs to hunt American subs in a limited, high-importance area. Because of that special mission, a sub duel was likely.

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Torpedoes also used magnetic pistols, which essentially lit the fuse when affected by the ship's magnetic field. But you are right, they were ship killers, not duelers. If you could put some reference to the events the book is based upon, it would be much appreciated. – rath Apr 17 '14 at 16:30
I was using the word "contact" losely. The torpedo had to be virtually in contact with the ship to explode, right next to it. As you say magnetic sensing was the operative trigger. – Tyler Durden Apr 17 '14 at 17:23
I would add the comment B******s, to use a non-homeing torpedo against another submarine you would need to know the depth and have that available as a depth setting for your torpedoes. For a target on the surface or known to be at PD this can work, otherwise not a chance. – Conrad Turner Feb 8 '15 at 8:51

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