On 22 June 1941 Hitler unleashed Operation Barbarossa the biggest military operation in human history. More than 3 million men of the Axis poured into the Soviet Union beginning a conflict, that even within the context of the Second World War, was unprecedented in both its scale and savagery. Operation Barbarossa began with unparalleled success for the Wehrmacht and its allies with millions of Soviet soldiers killed and captured in the opening months of this titanic struggle. But by the winter of 1941 and against all the odds the German war machine had been halted outside the gates of Moscow marking the beginning of the end for the Nazi regime. To better understand this enormous operation Dan is joined by the author and broadcaster Jonathan Dimbleby who has written a new book Barbarossa: How Hitler Lost the War. They discuss why Barbarossa was launched, the inhuman nature of the fighting and the horrific treatment of civilians and particularly the Jews, whether Barbarossa could have ever been successful and looking at the more human side behind the almost unbelievable scale of the fighting.