Hitler had proclaimed that Nazi conquered Europe was an impenetrable fortress. On the 6th of June 1944, the Allies launched the largest combined land, air and sea operation ever. This invasion, designed to begin the liberation of Europe, would forever be known as D-Day. The years leading up to 1944 had seen total domination of Europe by Nazi Germany. Despite the entry of America into WWII, strategic bombing, the invasions of North Africa and Italy, Germany remained in control and was able to strength its coastal defenses, The Atlantic Wall, in preparation for the inevitable Allied invasion. Operation Overlord was the Allied plan to defeat those defenses and open a Western Front. The hard lessons learned at Anzio, Dieppe and Salerno were about to be brought into focus with the greatest invasion the world had ever seen. But how had the Allies come to this point? Who were the personalities and what compromises were made to forge this great alliance?