Witold Pilecki was a Polish cavalry officer, intelligence agent, and resistance leader. Early in World War II he co-founded the Secret Polish Army resistance movement.
In 1940 Pilecki volunteered to allow himself to be captured by the occupying Germans in order to infiltrate the Auschwitz concentration camp. At Auschwitz he organized a resistance movement that eventually included hundreds of inmates, and he secretly drew up reports detailing German atrocities at the camp, which were smuggled out to Home Army headquarters and shared with the Western Allies.
Later, having escaped from Auschwitz, Pilecki fought in the Warsaw Uprising of August–October 1944. Following its suppression, he was interned in a German prisoner-of-war camp. After the communist takeover of Poland he remained loyal to the London-based Polish Government-in-Exile. In 1945 he returned to Poland to report to the Exile Government on the situation in Poland. Before returning, Pilecki wrote Witold's Report on the Auschwitz concentration camp, anticipating that he might be killed by Poland's new communist authorities.