The death of General Sikorski on July 4 , 1943 coincided with the disclosure by the Germans of the massacre of Polish officers in Katyn Forest by the Soviet NKVD . The appeal made to the International Red Cross by the Polish government-in-exile for an investigation of the atrocity was used by Stalin as a pretext to break off Polish-Russian diplomatic relations . This was a critical moment ; Poland 's historical and cultural heritage were now at risk from both the Soviet Union and Nazi Germany . After displacing the Red Army from the eastern regions of Poland , the Nazis occupied the entire country ; their aim was the destruction of Polish scholarship and cultural heritage . This plan was being implemented through the extermination of the middle class , the intelligentsia , systematic plundering of libraries and museums , and by forbidding cultural , educational , and artistic activities . These actions were reinforced by mass arrests and deportations to concentration camps ( such as Sonderaktion Krakau ) , which led to the murder of nearly all faculty of the Jagiellonian University . The closure of the Polish Academy of Sciences and other research and academic institutions left no doubt as to the Germans ' intentions
massacre of Polish officers
Katyn massacre
Józef Piłsudski Institute of America