Between 24 October and 23 November 1939, a total of 42,492 Polish prisoners of war were transferred from Kozelsk and Putyvl camps across the Nazi–Soviet demarcation line and handed over to the Germans. Both Gestapo and NKVD expected the emergence of Polish resistance and discussed ways of dealing with the clandestine activities of the Poles. In the immediate aftermath of the meeting, the Soviet NKVD began the collection of data leading to the Katyn massacre committed in the spring of 1940.