To think that the Americans destroyers provoked those subs in several occasions by detonating depth charges nearby without knwing their payload.
One of those submarines came close to launch that "special" torpedo because the inexperienced captain tought he was under attack and he didn't understood that the Americans were using underpowered practice charges just to rock the boat a little and make their presence felt. Good thing that the second in command was a war veteran that served on asw vessels and that could distinguish a firecracker from a true depth bomb!