Operation Drumbeat

(uboat.net) With the Japanese surprise attack on Pearl Harbour on Dec 7, 1941 Hitler was bound by a promise to Japan to also declare war on the US. He did so promptly on Dec 11 and after that all restrictions on German U-boats (which had been attacked and hunted by US convoy escorts in the North Atlantic for the last 5-6 months of 1941 anyway without permission to attack the US escorts) not to attack American shipping were removed. This opened up a whole new field for Dönitz which immediately drew up plans for a devastatingly swift blow on the US eastern seaboard. Continued