Russia's War: Blood Upon the Snow is one of the best documentaries I've ever seen (see also "Stalin: Man of Steel" DVD from the History Channel). It does a marvelous job explaining the prelude to the Nazi attack on the Soviet Union, especially the impact of the Stalinist purges in the late 1930s. The annihilation of the officer corps plus Stalin's disregard of warnings from the British and his own intelligence services (he had his own spies executed for warning of the pending Nazi attack)left Russia almost completely defenseless. Each episode begins with a brief introduction by Henry Kissinger, but the wonderful narration is by Nigel Hawthorne (Yes, Prime Minister). I check at least monthly to see if a DVD version has been released. So far, no luck.