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Events on Sunday 19 May 1940 1
1940Katyn massacreSoviet NKVD executes about 22,000 Polish prisonersBetween April and May the Soviet NKVD shot about 22,000 Polish officers, police and members of the intelligentsia in the Katyn Forest and at other sites. The Soviet Union blamed Nazi Germany for the killings until 1990. The massacre remains a defining grievance in Polish-Russian relations.