Hi Periscope Pete,

As the war progressed it became more and more dangerous for a U-boat to attack on the surface with the deck gun after damaging a ship with torpedoes. It became much more difficult to find merchant ships sailing alone and surfacing to use the deck gun against a merchant ship in a convoy was almost suicide because of the escorts and air cover. Also by this time a great many merchant ships were also armed and a U-boat wasn’t a very stable gun platform on the surface. Even one hit from an armed merchant ship could keep the U-boat from being able to dive and there wasn’t much chance of getting home alive if your U-boat couldn’t dive at that point in the war. In the latter stages many U-boats couldn’t even stick around long enough after an attack to confirm their kills. They reported them on the basis of hearing the explosions and “breaking up” sounds which frequently were incorrect.

Early on it was customary to surface and find out the details of the ship just attacked from the survivors in the lifeboats but that pretty much stopped for the same reasons as the war progressed. Allied control of the air, allied airborne and ship borne radar and the presence of more and better escorts made the deck gun obsolete. They did however need more AA guns and armor for the bridge and the deck guns were an obvious choice for removal along with their ammo in order to balance the added weight of the additional AA guns, AA ammo, and their gunners. More AA Guns required additional AA gunners which in turn required more food and other supplies. The added weight had to come from someplace.

Some U-boats were able to defend themselves against aircraft with their AA guns even shooting some down, however, as the allied air cover increased and enough allied planes became available, the allies developed tactics that made the AA guns pretty obsolete too. Multiple aircraft engaging the U-boat’s guns while others attacked from different directions (very much like the way the allies learned to do depth charge attacks) either sank the U-boat outright or caused it to dive. If it dived bombs, depth charges and / or FIDOs (acoustic homing torpedoes officially called mines) were dropped into or around the swell and very frequently that was the end of the U-boat.

Interestingly enough things came full circle. The allies used tactics similar to the wolfpacks against the U-boats. The first plane to spot a U-boat on the surface would call for others and not attack until a group of planes had arrived. Doenitz responded with convoy tactics for his U-boats. They were ordered to sail together on the surface along with a “flak trap” (a U-boat with especially heavy AA guns intended to act as an escort) to get through the Bay of Biscay. All of the U-boats were to stay surfaced and fight with their AA guns when attacked from the air thus forcing attacking aircraft to face the combined guns of multiple U-boats. The wolfpack tactics used by allied planes overcame this strategy ultimately resulting in very high loss rates among the U-boats. Doenitz didn’t have sufficient air power of his own to defeat the allied air power which would have been a better counter.

The Schnorchel seemed to offer a solution for Doenitz. It would allow the U-boats to not have to surface. However, in time the allied airborne radar was able to detect the head of the Schnorchel on the surface and a U-boat caught Schnorcheling was a pretty easy target. They tried mounting radar detectors on the Schnorchel but it was too little too late. The Type XXI would have made a difference for a while had there been time for it to become operational in numbers but by that time Germany was just too weak and the allies were just too strong. The allies also had newly developed technologies on the shelf like dipping sonar and magnetic anomaly detectors already.

The normal course of the war was move and counter move. One side developed something and the other side developed a counter to it then the first side developed a counter to the counter and the other side…………. By this time it was just too late for this process to work out in Germany’s favor. I guess we could speculate what the likely moves and counter moves would have been but this is a history forum and not the place to do that.

Regards,

Ken Dunn