Witold Pilecki was a soldier of the Second Polish Republic and founder of the Secret Polish Army (Tajna Armia Polska) a resistance group and a member of the Home Army (Armia Krajowa)
He was the author of the first Intelligence report on Auschwitz, which the Polish government-in-exile used to convince the Allies that the Germans were carrying out genocide of the Jewish people.
Pilecki volunteered to work for a Polish resistance operation in order to get himself arrested and imprisoned in the infamous Auschwitz death camp. Once there he gathered enough information to support his claims. In the meantime he organized a resistance movement among the Jewish inmates. The Allies were informed as early as 1940 on German atrocities. Three years later, Pilecki escaped and eventually took part in the Warsaw Uprising.
He was executed in 1948 by the Urzad Bezpieczenstwa, Stalin’s secret police, on charges of working for “foreign imperialism”, a euphemism for MI6.