World War II: The Second Happy Time of Hitler's submarines comes to an end, as the increasingly effective American convoy system compels them to return to the central Atlantic.

The Second Happy Time was a phase in the Battle of the Atlantic during which Axis submarines attacked merchant shipping and Allied naval vessels along the east coast of North America. The First Happy Time was in 1940–41 in the North Atlantic and North Sea. Adolf Hitler and Benito Mussolini declared…