And US torpedoes didn't work for the first two years. Meaning, they bounced and sank. Almost always. Two years. Apparently at some point somebody noticed that

And US torpedoes didn't work for the first two years. Meaning, they bounced and sank. Almost always. Two years. Apparently at some point somebody noticed that one that worked had hit at a shallow angle, and arranged for that until they got fixed torpedoes. My impression was that this was not communicated to other submariners. I don't know how long the trick was used.