Battle of the Atlantic

Convoy Routes in the Atlantic

On this map of the Battle of Atlantic, the approximate location of major convoy routes are indicated in dotted green lines.  Blue dots mark allied merchant shipping sunk between mid-March and December 1941.  The red dots indicate the known destruction of a German U-boat.  The solid black lines indicate the limits of allied air cover.  Under these conditions President Roosevelt and Prime Minister Churchill met at Argentia Bay, Newfoundland for the conference in which they drafted the Atlantic Charter, on August 9th through 12th, 1941.

More further reference see Jonathan Dimbleby's definitive account in The Battle of the Atlantic: How the Allies Won the War, published by Oxford Univeristy Press in 2016.