The Germans were quick to blame the Soviets for the massacre and invited international observers and forensic experts to inspect the site. The Soviets were equally quick to blame the Nazis. Britain and the USA, being unwilling to offend their Soviet allies, concurred with the Soviet view. Neither Churchill nor Roosevelt was willing to accept evidence to the contrary.
Letters, postcards, newspaper clippings and other items found on the bodies in the Katyn forest confirmed that the murders took place in the spring of 1940, well before the German army had arrived in the region.
Over 20,000 Polish military officers, police officers and intellectuals were murdered in 1940 at camps and prisons in Russia.
It was not until 2010 that the Russian Dumas (parliament) officially admitted that the Stalinist regime was to blame and that Stalin had personally ordered the executions.