Hi Jt,

The problem wasn’t as simple as just torpedoing the escorts.

Until the T5 acoustic torpedo was available the U-boats didn’t have an effective weapon against an escort and even then the T5 wasn’t very effective against them either.

There were several problems.

First the escorts were very small, fast and agile compared to a merchant ship and they made very difficult targets. Compared to a merchant ship they were very shallow draft and required that the torpedoes be set to run at a very shallow depth where they were the most sensitive to the sea state. The closer to the surface they ran (to compensate for the escort’s shallow draft) the more likely they were to be affected by the waves etc and the more likely they were to broach or simply be pushed off their course – especially in rough seas. To complicate matters even more the torpedoes began the war with some serious depth keeping defects and the magnetic detonators (which might have been able to compensate for the shallow draft of the escorts had they worked correctly) also were prone to premature detonation and also could be defeated to some extent by degaussing.

Additionally, escorts soon had asdic which allowed them to hear the high speed propellers of the torpedoes almost as soon as they were fired and take immediate action and the escorts unlike a slow merchant ship had the speed and agility to get out of the way. Not only that but if you fired a torpedo at a merchant ship and missed, the merchant ship would generally try to run away however an escort would more than likely turn toward you and attack you at high speed while presenting a tiny bow on target that was moving toward you very fast. Meanwhile since you had to be either surfaced or at periscope depth when you fired your torpedoes, you wouldn’t have much time to dive deep enough to evade the impending depth charge attack.

Also, though most of the escorts were not destroyers they were much smaller and slower frigates, corvettes or sloops, a destroyer might be able to do 30 knots or so – the same speed the G7e torpedoes were normally set to run. The G7a was normally set to run at 40 knots but it left a bubble trail telling the escort exactly where you were.

Later in the war when the T5s were available the U-boats were ordered to try to take out the escorts first and they had some success but by that time it was already too late to make a significant difference – there were too many escorts and they had the very effective “Foxer” acoustic torpedo decoy to draw the T5s away from them. As the U-boats had to dive immediately upon firing a T5 to prevent a defective T5 from homing on the U-boats propeller noises instead of the intended target they didn’t actually observe the detonation of the torpedo and didn’t realize that it had detonated in the wake of the escort instead of hitting it so they reported successes they didn’t really have.

Had Doenitz realized that the T5 wasn’t the escort killer he thought it was he may not have issued the order to attack the escorts at all.

Regards,

Ken Dunn