In March 1937 Pius XI published two encyclicals five days apart. Mit brennender Sorge, with burning concern, was written in German rather than Latin, smuggled into Germany and read from Catholic pulpits on Palm Sunday before the authorities could stop it. It accused the German government of breaking the concordat of 1933 article by article, and condemned the exaltation of race, people or state above their proper worth as an idolatry that overturns the order made by God. Divini Redemptoris followed, condemning atheistic communism in equally absolute terms and defending the dignity of the person against the collectivity.
The same year he moved further. He commissioned three Jesuits to draft an encyclical on the unity of the human race, later known as Humani Generis Unitas, intended to address racism and antisemitism directly. A text was prepared and reached Rome, but Pius XI died on 10 February 1939 before issuing it, and it was not published by his successor. Historians disagree about the draft's adequacy, since parts of it repeat old theological hostility to Judaism even while rejecting racial theory, but its existence is documented and it is often called the hidden encyclical.
In September 1938, receiving Belgian pilgrims and speaking of the words of the Roman Canon that name Abraham as our patriarch, he broke off and said that antisemitism is a movement in which Christians can have no part, because spiritually we are all Semites. The remark was reported in the Belgian Catholic press but was left out of the Vatican's own newspaper, which is itself part of the historical record of how far the church went and how far it did not.