Jan Karski, was a Polish World War II resistance fighter and scholar. He visited the Warsaw Ghetto after the summer 1942 deportations. Disguised as a guard, he then managed to enter what he thought was the Bełżec death camp for one day where he witnessed mass murder. In 1942 and 1943 Karski reported to the Polish government in exile and the British and U.S. governments on the situation in Poland, especially the destruction of the Warsaw Ghetto and the extermination camps. Wikipedia
The definitive Wikipedia entry for Jan Karski. Wikipedia is the biggest multilingual free-content encyclopedia on the Internet. en.wikipedia.org/wiki/Jan_Karski
