It’s early 1942 and Hitler has declared war on the United States.
Dönitz sends his U-boats to the mostly unprotected US east coast while slowly but surely the Allies start to implement new anti-submarine warfare technology.
The Kriegsmarine was not ready and Karl Dönitz knew it. But there was no escaping Hitler’s war. The U-boats would have to make do.
We’re in the Interbellum. While one half of the world was done with war, the other half was gearing up for a new one.