 Complete the following phrase:  On 4 July 1943 the Polish Prime Minister-in-Exile, General Wladyslaw Sikorski, who was also Commander-in-Chief of the Polish Armed Forces in the West, died in an air crash off Gibraltar as he was returning to England from an inspection tour of Polish forces in the Mediterranean theatre. Until the Germans April 1943 discovery of mass graves of 28,000 executed Polish military reserve officers at Katyn, near Smolensk in Russia, Sikorski had wished to work with the Soviets. After 