In April 1943, the Germans discovered the graves of 4,000 or more Polish officers at Katyn near Smolensk. The Polish government, suspecting the Soviets to be the perpetrators of an atrocity, requested the Red Cross to investigate. The Soviets denied involvement and the request was soon withdrawn by Sikorski under British and American pressure, but Stalin reacted by "suspending" diplomatic relations with the Polish Government-in-Exile on 25 April. The Katyn massacre information was suppressed during and after the war by the British, to whom the revelation was an embarrassment and presented a political difficulty.
