Below is a statement by United Nation (What the Allied Powers called themselves) following a report that they received from the Polish Government-in-Exile ion December of 1942.

"The above-mentioned Governments and the French National Committee condemn in the strongest possible terms this bestial policy of cold-blooded extermination. They declare that such events can only strengthen the resolve of all freedom- loving peoples to overthrow the barbarous Hitler tyranny. They re-affirm their solemn resolution to ensure that those responsible for these crimes shall not escape retribution, and to press on with the necessary practical measures to this end."

A number of things can be determined from this statement. First, by 1942 there was ample evidence to either lead to the statement or force the statement. Next, the response to the atrocities was NOT to save the victims, but to prosecute the war in order to bring the responsible parties to justice. Finally, the statement demonstrates that there was already some idea regarding some form of war crimes trials.

While the statement does not mention camps, the timing of the report by the Polish Government-in-Exile suggests that the statement is in reference to Aktion Reinhardt, a plan which instituted the first extermination camps and was responsible for the extermination of most of the remaining Polish Jews.

There is also ample evidence that the world knew of anti-Jewish policies of the Nazis during the years before WWII. Newspapers consistently reported on such policies as early as March of 1933, only slightly over a month after Hitler took office. One US newspaper quoted Secretary of State Cordell Hull as stating, "that following so far-reaching a political readjustment as has recently taken place, some time must elapse before a state of equilibrium could be reestablished. In the opinion of the Embassy such a stabilization appears to have been reached in the field of personal mistreatment [of Jews], and there are indications that in other phases the situation is improving.” Clearly much was known by the US government prior to the war.

In response to Reichskristallnacht (Night of the Broken Glass), a pogrom organized by the SA in 1938, the United Press stated, “Germany’s extreme anti-Jewish measures again monopolized the attention last night of European diplomats. But most of them are keeping discreetly silent, so-far as the public is concerned. They are fearful that any comment may disturb the delicate balance of European diplomacy at a time when general appeasement is hoped for.” In both this case and that of Cordell Hull's statement, we can see that the US government took the approach that the persecution of the Jews was secondary to stability in Europe. During the war, the extermination of the Jews was secondary to victory in Europe.

Source

“Conference at Geneva is Again Opened,” Plattsburgh Daily Press, September 26, 1933.

United Press, “British, French Press Bare Public Indignation of Nazi Attacks Upon the Jews,” Plattsburgh Daily Republican, November 14, 1938, accessed June 9, 2014.

Polish Ministry of Foreign Affairs. The Mass Extermination of Jews in German Occupied Poland. London: Hutchinson & Co., 1942.