Long-buried Vatican files reveal a new and shocking indictment of World War II’s Pope Pius XII: that in pursuit of absolute power he helped Adolf Hitler destroy German Catholic political opposition, betrayed the Jews of Europe, and sealed a deeply cynical pact with a 20th-century devil.

One evening several years ago when I was having dinner with a group of students, the topic of the papacy was broached, and the discussion quickly boiled over. A young woman asserted that Eugenio Pacelli, Pope Pius XII, the Pope during World War II, had brought lasting shame on the Catholic Church by failing to denounce the Final Solution. A young man, a practicing Catholic, insisted that the case had never been proved.

Raised as a Catholic during the papacy of Pius XII—his picture gazed down from the wall of every classroom during my childhood—I was only too familiar with the allegation. It started in 1963 with a play by a young German named Rolf Hochhuth. Der Stellvertreter (The Deputy), which was staged on Broadway in 1964, depicted Pacelli as a ruthless cynic, interested more in the Vatican’s stockholdings than in the fate of the Jews. Most Catholics dismissed Hochhuth’s thesis as implausible, but the play sparked a controversy which has raged to this day.

Disturbed by the anger brought out in that dinner altercation, and convinced, as I had always been, of Pius XII’s innocence, I decided to write a new defense of his reputation for a younger generation. I believed that Pacelli’s evident holiness was proof of his good faith. How could such a saintly pope have betrayed the Jews? But was it possible to find a new and conclusive approach to the issue? The arguments had so far focused mainly on his wartime conduct; however, Pacelli’s Vatican career had started 40 years earlier. It seemed to me that a proper investigation into Pacelli’s record would require a more extensive chronicle than any attempted in the past.

So I applied for access to archival material in the Vatican, reassuring those who had charge of crucial documents that I was on the side of my subject. Six years earlier, in a book entitled A Thief in the Night, I had defended the Vatican against charges that Pope John Paul I had been murdered by his own aides.

Two key officials granted me access to secret material: depositions under oath gathered 30 years ago to support the process for Pacelli’s canonization, and the archive of the Vatican Secretariat of State, the foreign office of the Holy See. I also drew on German sources relating to Pacelli’s activities in Germany during the 1920s and 1930s, including his dealings with Adolf Hitler in 1933. For months on end I ransacked Pacelli’s files, which dated back to 1912, in a windowless dungeon beneath the Borgia Tower in Vatican City. Later I sat for several weeks in a dusty office in the Jesuit headquarters, close to St. Peter’s Square in Rome, mulling over a thousand pages of transcribed testimony given under oath by those who had known Pacelli well during his lifetime, including his critics.

By the middle of 1997, I was in a state of moral shock. The material I had gathered amounted not to an exoneration but to an indictment more scandalous than Hochhuth’s. The evidence was explosive. It showed for the first time that Pacelli was patently, and by the proof of his own words, anti-Jewish. It revealed that he had helped Hitler to power and at the same time undermined potential Catholic resistance in Germany. It showed that he had implicitly denied and trivialized the Holocaust, despite having reliable knowledge of its true extent. And, worse, that he was a hypocrite, for after the war he had retrospectively taken undue credit for speaking out boldly against the Nazis’ persecution of the Jews.