Just days before Christmas 1944, a quarter of a million German troops launched a shattering offensive through the Ardennes. Allied troops were taken completely off guard. They thought the war was almost over; only to find themselves engulfed in one of the greatest land battles of the 20th Century. At first, Hitler's Ardennes Offensive was successful, but nearly two months of fighting left the German Army in ruins. In this programme scientists and historians investigate why the Battle of the Bulge ended in total defeat for Germany.