.- Pope Pius XII's secret support for the attempted overthrow of Nazi dictator Adolf Hitler is the subject of a recent book that draws on wartime documents and interviews with the American intelligence agent who wrote them.

“This book is the truth – as best I could establish it in a number of years of research – about the Pope’s secret operations in World War II,” historian Mark Riebling told CNA earlier this year.

“Its main premise is that Pius opted to resist Hitler with covert action instead of overt protest. As a result, he became involved in three separate plots by German dissidents to remove Hitler.”

“I thought this idea – that the Church engaged in secret operations during the bloodiest years in history, in the most controversial part of its recent history – was not just a footnote; it was something worth pursuing,” he said.

Riebling tells this story in his book “Church of Spies: The Pope's Secret War Against Hitler,” published by Basic Books in September 2015.

In the late 1990s, debate over whether Pius XII did enough to counter the Nazis reached a high point with the publication of the deeply controversial book, “Hitler's Pope,” by British journalist John Cornwell. The book was highly critical of Pius XII, charging that he was culpably silent – if not an accomplice – in the rise of Nazism.

“If you read the fiercest critics of the Nazi-era Church, the major ones all concede that Pius XII hated Hitler and worked secretly to overthrow him,” Riebling said. “Yet they say this in their books in just a clause, a sentence, or a paragraph. To me, this episode merited more curiosity.”

“If 'Hitler's Pope' wanted to help rid the world of Hitler, what's the story?”

Riebling said there were several sources of inspiration for the book. During his Catholic upbringing, he learned the long history of the Church: in its first centuries, Christianity was an underground organization. In post-Reformation England, the Jesuits were involved in clandestine work.

This history prompted him to ask how a historian would document it and find evidence.

He also drew inspiration from the story of James Jesus Angleton, a famous U.S. intelligence officer who during World War II ran an operation to penetrate the Vatican for the Office of Strategic Services, the Central Intelligence Agency’s predecessor.

During research on his previous book, “Wedge: The Secret War between the FBI and CIA,” Riebling discovered wartime documents from Angleton's Rome section of the Office of Strategic Services.

“There were at least ten documents implicating Pius XII and his closest advisers in not just one, but actually three plots to remove Hitler – stretching from 1939 to 1944. These were typed up by someone using a very distinct nickname.”

That nickname, “Rock,” belonged to Ray Rocca. Rocca served as Angleton's deputy in Rome and for most of his later career. His career included responsibility for the Central Intelligence Agency's records concerning the 1963 assassination of President John F. Kennedy.

“So, here's a guy who had been in the Vatican; who had been charged with penetrating the Vatican; and who knew a thing or two about assassination probes. I thought: here’s an interesting guy to get to know,” Riebling said. Rocca did not violate his oath of secrecy, but his interviews with Riebling are among the book's sources.

According to Riebling, his book does not charge that the Pope “tried to kill Hitler.” Rather, the Pope’s actions were more subtle.

“Pius becomes a key cog in conspiracies to remove a ruler who is a kind of Antichrist, because good people ask for his help, and he searches his conscience, and he agrees to become an intermediary for the plotters – their foreign agent, as it were – and thereby he becomes an accessory to their plots.”

The historian described these actions as “some of the most astonishing events in the history of the papacy.”

Pius XII had connections with three plots against Hitler. The first, from October 1939 to May 1940, involved German military conspirators. From late 1941 to spring of 1943 a series of plots involving the German Jesuits ended when a bomb planted on Hitler’s plane failed to explode.

The third plot again involved German Jesuits and also German military colonel Claus von Stauffenberg. Although the colonel successfully planted a bomb near the Nazi dictator, it failed to kill Hitler. The priests had to flee after the failed attempt. Those unable to escape were executed.

During his research, Riebling discovered that Pius XII secretly recorded the conversations held in his office. Transcripts of the Pope's talks with German cardinals in March 1939 show that he was deeply concerned that German Catholics would choose Hitler instead of the Church.

“The cardinals asked Pius to appease Hitler, so that German Catholics won’t break away and form a state church, as happened in Tudor England,” Riebling said.

“Pius heeded the German episcopate's advice. Instead of protesting openly, he would resist Hitler behind the scenes.”

Pius XII's agents provided the Allies with useful intelligence about Hitler's war plans on three occasions, including Hitler’s planned invasion of Russia. In all three cases, the Allies did not act on the information.

For their part, the Nazis regarded Pius XII with suspicion since his election in 1939.

“He worked hard to allay those suspicions, to minimize persecutions of German Catholics. But the Nazis never dropped their guard,” Riebling said.

At one point Hitler planned to invade the Vatican, kidnap the Pope and bring him to Germany. Leading Nazi Heinrich Himmler “wanted to have the Holy Father publicly executed to celebrate the opening of a new soccer stadium,” Riebling said.

“Pius became aware of these plans, through his secret papal agents; and, in my view, that influenced the Holy Father’s decision to become involved with the anti-Nazi resistance.”

For Riebling, the assassination plots against Hitler were an admission of weakness, “because it’s saying that we can’t solve the problem by some other means.”

“Knowing what I do about Pius XII, and having researched him for many years, I believe he wanted to be a saint. He wanted people in Germany to be saints,” he added.

“When he heard that a priest was arrested for praying for the Jews and sent off to a concentration camp, he said: 'I wish everyone would do that.'”

“But he didn't say it publicly,” the writer acknowledged. The Pope's words were made in secret in a letter to a German bishop.

“So I think what really happened here is: Pius XII wanted to lead a Church of saints. But had to settle for a Church of spies.”

This article was originally published on CNA Feb. 5, 2016.