The Polish government-in-exile in London learned about the extermination camps from the Polish leadership in Warsaw, who from 1940 "received a continual flow of information about Auschwitz", according to historian Michael Fleming. This was in large measure thanks to Captain Witold Pilecki of the Polish Home Army, who allowed himself to be arrested in Warsaw and spent 945 days in Auschwitz from September 1940 until April 1943, organizing the resistance movement inside the camp.
Mengele sailed to Argentina in July 1949, assisted by a network of former SS members. He initially lived in and around Buenos Aires, then fled to Paraguay in 1959 and Brazil in 1960, while being sought by West Germany, Israel, and Nazi hunters such as Simon Wiesenthal who wanted to bring him to trial. He eluded capture in spite of extradition requests by the West German government and clandestine operations by the Israeli intelligence agency Mossad. He drowned in 1979 after suffering a stroke while swimming off the Brazilian coast, and was buried under a false name. His remains were disinterred and positively identified by forensic examination in 1985.