From Wikipedia: Władysław Eugeniusz Sikorski was a Polish military and political leader.Prior to World War I, he established and participated in several underground organizations that promoted the cause of Polish independence. He fought with distinction in the Polish Legions during World War I, and later in the newly created Polish Army during the Polish-Soviet War (1919 to 1921). In that war he played a prominent role in the decisive Battle of Warsaw.  During World War II he 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 dictator 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 his death have been disputed, and given rise to a number of conspiracy theories surrounding the crash and his death. Investigators later concluded that Sikorski's injuries were consistent with a plane crash.