In the prelude to the Holocaust , Popes Pius XI and Pius XII preached against racism and war in encyclicals such as '' Mit brennender Sorge '' ( 1937 ) and '' Summi Pontificatus '' ( 1939 ) . Pius XI condemned '' Kristallnacht '' and rejected the Nazi claim of racial superiority , saying instead there was only " a single human race " . His successor Pius XII employed diplomacy to aid the Jews , and directed his Church to provide discreet aid . While the overall caution of his approach has been criticised by some , his 1942 Christmas radio address denounced the murder of " hundreds of thousands " of innocent people on the basis of " nationality or race " and he intervened to attempt to block Nazi deportations of Jews in various countries . When the Nazis came for Italy 's Jews , some 4715 of the 5715 Jews of Rome found shelter in 150 Church institutions , 477 in the Vatican itself and he opened his Castel Gandolfo residence , which took in thousands
Kristallnacht
Kristallnacht
Rescue of Jews by Catholics during the Holocaust