With unprecedented access to thousands of top secret aerial photographs, compelling story telling, state of the art graphics and dramatic reconstruction, historian Dan Snow examines the incredible events of 6th June 1944. Nothing less than the freedom of the western world was at stake as the Allies launched the largest amphibious assault in history. Dan Snow examines how two years of meticulous planning, espionage and the analysis of millions of aerial photographs shaped the outcome of this day of days and hears the testimonies of those who risked their lives to save the world from Nazi tyranny.