Witold Pilecki was providing the Polish underground authorities reports on the situation in KL Auschwitz – for the first time, as early as October of 1940 – which were forwarded to the government in London. After his 1943 escape, Pilecki wrote two reports and in 1945, after the war, he prepared the third one which contained an extensive account of his camp ordeal. Pilecki’s reports are extraordinary documents of how the Polish clandestine military organization functioned in KL Auschwitz, as well as a moving account of an eye-witness of Nazi crimes.