It was the biggest bloodiest and bitterest battle ever fought. It cost the lives of at least 20 million people and ended Europe's dominance in world affairs. It was the head on clash of the two mightiest armies Man has ever known - and in sheer numbers, miles of front, and quantity of guns, shells and tanks, no other battle in history can compare with it. Certainly there will never be another like it. Although Hitler's opening attack on Russia in June 1941 -codenamed by the German Army "Operation Barbarossa" - forms the climax of the narrative, this documentary is concerned more with the background and build up to that assault. Unique archive material from both sides of the Iron Curtain has been incorporated, together with notable contributions from some of the participants, such as Albert Speer, Hitler's close confidant and munitions chief, General Warlimont who planned the campaign and served at Hitler's headquarters throughout the War, General von Manteuffel, who helped cany out the scheme, and Dr. Paul Schmidt who was Hitler's individual interpreter.