"During the Second World War, Sikorski became Prime Minister of the Polish government-in-exile, Commander-in-Chief of the Polish Armed Forces, and a vigorous advocate of the Polish cause in the diplomatic sphere. He supported the reestablishment of diplomatic relations between Poland and the Soviet Union, which had been severed after the Soviet pact with Germany and the 1939 invasion of Poland—however, Soviet leader Joseph Stalin broke off Soviet-Polish diplomatic relations in April 1943 following Sikorski's request that the International Red Cross investigate the Katyń Forest massacre. In July 1943, a plane carrying Sikorski plunged into the sea immediately after takeoff from Gibraltar, killing all on board except the pilot. The exact circumstances of Sikorski's death have been disputed and have given rise to a number of different theories surrounding the crash and his death. Sikorski had been the most prestigious leader of the Polish exiles, and his death was a severe setback for the Polish cause."
Another honored ally,