Shortly after Germany had invaded Poland in the early autumn of 1939, the Soviet Union occupied the eastern half of that country and rounded up a large part of the Polish political and military elite. A short while later, Stalin himself ordered the liquidation of all these captives. On receiving clues from Poles about these massacres, the Germans managed to locate one set of the mass graves near the Polish town of Katyn in 1943, and later another set in Vynnytsia. What followed was an exemplary investigation of the material traces of this mass murder by an international independent commission, something never seen with respect to alleged German war crimes. The results of this investigation were used by Germany to shore up its propaganda efforts against Soviet Russia. After the war, however, Russia tried to pin this war crime on Germany. Only in 1990 did Russia officially admit Stalin’s guilt.