During World War II, he volunteered for a Polish resistance operation to get imprisoned at Auschwitz in order to gather intelligence and escape. While in the camp, Pilecki organized a resistance movement and as early as 1941, informed the Western Allies of Nazi Germany's Auschwitz atrocities. He escaped from the camp in 1943 and took part in the Warsaw Uprising. He remained loyal to the London-based Polish government-in-exile and was executed in 1948 by the Stalinist secret police Urząd Bezpieczeństwa on charges of working for "foreign imperialism", thought to be a euphemism for MI6. Until 1989, information on his exploits and fate was suppressed by the Polish communist regime.