What was the impact of the normandy landings on the allied war effort during world war ii? a. the normandy landings were so devastating to the allied forces that the germans were able to cross the english channel and invade the united kingdom. b. german forces retreated from france after the normandy invasion but were later able to invade france again after their victory in the ardennes forest. c. the massive amount of allied forces landing in normandy caused the german army to retreat and the allies to reclaim france. d. the normandy landings caused so many allied casualties that allied forces were forced to retreat from france.