History

Relative to their impact on both WWI and WWII, German U-boat strategy seems underweighted in discussions.

I think it is important to mention the advantages first, the submarines were relatively easier to build than, for example, a battleship cruiser etc. and could evade the fight with the royal navy which was clearly superior as well as build up pressure on the merchant ships that supplied England

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Among other things, I think it is also important to talk about the RAF, which also caused many problems for the Germans, be it air reconnaissance or support. These factors combined with the fact that the High Seas Fleet in Norway had losses, the submarines alone could not do enough to do long term damage to England

The big problem for the Kriegsmarine was that they were facing one of the best and largest naval powers of the time. In addition, there were serious mistakes in their command level (Bismarck as an example) 
The submarines were effective but could not build up enough pressure

That really is a very accurate comparison