Complex weather patterns and varied Allied forecasting techniques posed challenges that were overcome prior to D-Day. Here's What You Need to Know: Overlord succeeded in no small part because of the weather support the SHAEF commanders received. Operation Overlord, the cross-Channel attack that hit the Nazi-occupied beaches of Normandy in 1944, was the culmination of a grand strategy adopted early in the war, followed sporadically during the years of conflict, and aimed at defeating Hitler’s Reich by striking directly at Germany by invasion. As such, it was the culmination of a long series of difficult negotiations among the Allies, ultimately setting the stage for final victory. For the Anglo-Americans, Overlord was the decisive campaign of the European Theater.