This book introduces the reader to the evidence, thanks to which you can find out that Joseph Stalin and the leaders of the Soviet country did not shoot tens of thousands of Polish prisoners of war in April-May 1940. This event is known in history as the "Katyn execution." In April-June 1943, the Nazis dug up thousands of bodies of Polish officers in the western part of the USSR. The Nazis claim that the Soviet Union executed these officers in 1940. This version was immediately adopted by the Polish government in exile, in London, known for its ardent anti-communist sentiments.