On 5 March 1940 , after the Gestapo – NKVD Third Conference was held in Zakopane , Beria sent a note ( no. 794/B ) to Stalin in which he stated that the Polish prisoners of war kept at camps and prisons in western Belarus and Ukraine were enemies of the Soviet Union , and recommended their execution . Most of them were military officers , but there were also intelligentsia , doctors , priests , and others in a total of more than 22,000 people . With Stalin 's approval , Beria 's NKVD executed them in what became known as the Katyn massacre
Katyn massacre
Katyn massacre
Lavrentiy Beria