The issue of why Auschwitz concentration camp was not bombed by the Allies during World War II continues to be explored by historians.
"The Polish Government — as the representatives of the legitimate authority on territories in which the Germans are carrying out the systematic extermination of Polish citizens and of citizens of Jewish origin of many other European countries — consider it their duty to address themselves to the Governments of the United Nations, in the confident belief that they will share their opinion as to the necessity not only of condemning the crimes committed by the Germans and punishing the criminals, but also of finding means offering the hope that Germany might be effectively restrained from continuing to apply her methods of mass extermination." – Edward Bernard Raczyński (1891–1993) note to United Nations, 10 December 1942.
In 1942 Jan Karski reported to the Polish, British and U.S. governments on the situation in Poland, especially the Liquidation of the Warsaw Ghetto and the general systematic extermination of the Jews nationally. However, he did not know of the existence of gas chambers, instead repeating the belief (common at the time) that Jews were being killed with electricity. He met with Polish politicians in exile, including the Prime Minister, Władysław Sikorski, as well as with members of political parties such as the Socialist Party, National Party, Labor Party, People's Party, Jewish Bund and Poalei Zion. He also spoke to Anthony Eden, the British Foreign Secretary, and included a detailed statement on what he had seen in Warsaw and in Bełżec. In 1943 in London he met the author and journalist Arthur Koestler. He then traveled to the United States and reported to President Franklin D. Roosevelt. FDR reacted to Karski's report by inquiring jokingly into animal rights abuses (specifically, horses). His report was a major factor in informing the West.