Worldwide convoy coverage narrowed the U-boats' choices

Large numbers of destroyer escorts allowed the Allies to extend convoy protection beyond the principal North Atlantic routes. Protected traffic also crossed the South Atlantic, Indian Ocean, and Pacific, reducing opportunities for submarines seeking easier targets. Mercogliano argues that this global network helps explain Germany's concentration of U-boats in the Mid-Atlantic in 1943, where the air gap still offered an advantage. Allied hunter-killer forces could then concentrate against them. The subsequent dispersal of German submarines followed a campaign shaped by the number and distribution of escorts.