Hitler's Pope: The Secret History of Pius XII by John Cornwell

Backed by a wealth of new research, John Cornwell tells for the first time the story of the World War II career of Eugenio Pacelli, the man who was Pope Pius XII, arguably the most dangerous churchman in modern history. In the first decade of the century, as a brilliant young Vatican lawyer, Pacelli helped shape a new ideology of unprecedented papal power in Germany. In 1933 Hitler became his negotiating partner, an agreement was arranged that granted religious and financial payments to the Catholic Church in exchange for their withdrawal from social and political privilege, ensuring the rise of Nazism.