Pope Pius XII was pope from 1939 until 1958. He was born Eugenio Maria Giuseppe Giovanni Pacelli. He was ordained in 1899. He worked in the Vatican Secretariat of State and became a cardinal in 1929. He was the papal nuncio in Munich and Berlin during the 1920s, and was appointed as Pope Pius XI's secretary of state in 1930. He was the chief architect and negotiator of the Reich Concordat, the treaty between the Vatican and Hitler, signed in 1933 which helped the Nazis secure their hold on German government unopposed by the powerful Catholic community. This agreement was the primary reason that the Catholic Center Party was disbanded and the community lost all political leverage in the Reich. On March 2, 1939, he was elected to succeed Pius XI as pope.

Controversy surrounds Pius XII's silence during World War II concerning the extermination of the Jews by Nazi Germany. In a recent book, Hitler’s Pope: The Secret History of Pius XII, author John Cornwell portrays Pius XII as an authoritarian who was primarily concerned with increasing papal power. His reticence during the Holocaust was typical of his antipathy towards Jews in general. Cornwell provides convincing evidence of the Pope’s reluctance to encourage opposition among the German Catholics against the National Socialists even when the Nazis repeatedly broke with the terms of the Reich Concordat. The lack of opposition through the 1930s and the Second World War has been credited to the fear of persecution of the Catholic minority by the Nazis. However, even as late as 1942, the Catholic community was successful in protesting the euthanasia programs of the Nazis and these had to be stopped, for the most part, or taken underground. Pius XII also failed to publish the encyclical of Pius XI, Humani generis unitas (The Unity of the Human Race), after the death of Pius XI. The encyclical was the result of Pius XI’s growing concern about the National Socialists and anti-Semitism.