A German army still fighting in France cannot prepare Operation Barbarossa on the historical schedule, so there is no immediate eastern front to supply. Allied tanks, vehicles, and shipping otherwise sent through Arctic convoys can remain in the western war, as can resources historically committed to North Africa. Germany also loses the French factories and captured lorries that supported its later logistics and receives no pause to rebuild after the 1940 campaign. Those changes magnify a transport system that was already fragile at the end of its advance across France. Continued Allied use of French airfields would also extend fighter cover for bomber routes toward Germany.
Chapter · 2:15:36-2:17:57
No eastern front redirects Allied resources
A continuing western war removes the Arctic convoy effort and concentrates matériel in France while denying Germany captured French trucks.