After the signing of the Molotov – Ribbentrop Pact on 23 August 1939 , Germany invaded Poland on 1 September 1939 , and the Soviet Union invaded Poland on 17 September , resulting in the occupation of Poland by the Soviet Union and Nazi Germany . The first Gestapo – NKVD meeting took place in Brześć nad Bugiem ( Brest ) reportedly on 27 September 1939 , while some units of the Polish Army were still fighting ( see : Invasion of Poland ) resulting in mass internment of soldiers and their extrajudicial shootings on both sides of the Curzon Line . At the meeting , the German and Soviet officials reached a mutual agreement about the fate of Polish infantry soldiers captured by the Red Army . 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
Katyn massacre
Katyn massacre
Gestapo–NKVD conferences