Some claim that the full extent of what was happening in German-controlled areas was not known until after the war. However, numerous rumors and eyewitness accounts from escapees and others gave some indication that Jews were being killed in large numbers. Since the early years of the war the Polish government-in-exile published documents and organised meetings to spread word of the fate of the Jews. By early 1941, the British had received information via an intercepted Chilean memo that Jews were being targeted, and by late 1941 they had intercepted information about a number of large massacres of Jews conducted by German police. In the summer of 1942 a Jewish labor organization (the Bund) got word to London that 700,000 Polish Jews had already died, and the BBC took the story seriously, though the United States State Department did not take the news seriously[31]. By the end of 1942, however, the evidence of the Holocaust had become clear and on December 17, 1942 the Allies issued a statement that the Jews were being transported to Poland and killed. The US State Department was aware of the use and the location of the gas chambers of extermination camps, but refused pleas to bomb them out of operation. On May 12, 1943, Polish government-in-exile and Bund leader Szmul Zygielbojm committed suicide in London to protest the inaction of the world with regard to the Holocaust, stating in part in his suicide letter:
I cannot continue to live and to be silent while the remnants of Polish Jewry, whose representative I am, are being killed. My comrades in the Warsaw ghetto fell with arms in their hands in the last heroic battle. I was not permitted to fall like them, together with them, but I belong with them, to their mass grave.
By my death, I wish to give expression to my most profound protest against the inaction in which the world watches and permits the destruction of the Jewish people.
Debate also continues on how much average Germans knew about the Holocaust. Recent historical work suggests that the majority of Germans knew that Jews were being indiscriminately killed and persecuted, even if they did not know of the specifics of the death camps. Robert Gellately, a historian at Oxford University, conducted a widely-respected survey of the German media before and during the war, concluding that there was "substantial consent and active participation of large numbers of ordinary Germans" in aspects of the Holocaust, and documenting that the sight of columns of slave laborers were common, and that the basics of the concentration camps, if not the extermination camps, were widely known[32].
http://en.wikipedia.org/wiki/Holocaust#Who_knew_about_the_killings.3F