June 6, 1944. Operation Overlord was a colossal undertaking. 150,000 Allied Forces landed on five beaches in Normandy, France. It was the first phase in the liberation of Western Europe. When GIs from the First U.S. Army landed, the Allies believed the Germans would withdraw to the Seine. The American Forces would then advance to Brittany, the banks of the Loire, and Paris, but they were wrong!