The start of the pontificate of Pius XII occurred at the time of the Second World War and the Nazi Holocaust, which saw the industrialized mass murder of millions of Jews and others by Adolf Hitler‘s Germany. Pius employed diplomacy to aid the victims of the Nazis during the war and, through directing his Church to provide discreet aid to Jews and others, saved hundreds of thousands of lives. …
Some post-war critics have accused Pius of either being overly cautious, or of “not doing enough,” or even of “silence” in the face of the Holocaust. Yet, by the writings of Jewish men and women and mainly the Israeli State archives, it is well established that Pope Pius XII supervised a secret rescue network which saved approximately 800,000 Jewish lives. …
Certainly the Catholic Church could have done much more to distance themselves from Adolf Hitler and the NAZIs.
Rick McCharles 
Why did Pius XII not condemn the holocaust during the war? Because his priests were not saying to him that these concentration camps were extermination centers. Why did they not inform him of these terrible “death” camps? Because these camps were work and transit camps as the forensic examinations since the fall of Communism have shown.