John Cornwell, the author of the “Hitler’s Pope,” has backed away from some of the more sensational assertions he made in his best-selling book about Pius XII. But, then, his money has already arrived safely at his bank, and he’s also locked that presumably lucrative gig at Vanity Fair as a – gasp – Vatican correspondent. Predictably, his qualifiers and recantations, unlike his accusations, have been underreported.

If Rabbi David Dalin’s new book (Regnery, 161 pages, $27.95) does nothing more than call attention to the poor quality of scholarship supporting so much of the criticism of Pius XII, it will have accomplished a great deal. But what may be most breathtaking is Pius’s steep and sudden fall in reputation, from universally praised humanitarian at the end of World War II to the “Pope of Silence,” who, at best, ignored the plight of Europe’s Jews or, at worst, was a useful tool for the Nazis.

Rabbi Dalin traces the decline to a highly controversial 1963 play, “The Deputy,” written by Rolf Hochhuth, a former Hitler Youth turned left-wing activist. The Hochhuth play is a polemical screed and offers no historical evidence, but it was a highly effective detonator. Was it also Soviet agitprop? The author briefly references a possible connection, but more information would be helpful. Even before the end of the war, the Soviet machine was cranking overtime on a pontiff whose anti-communist bona fides were unquestioned and sure to get in the way of Moscow’s plans for postwar Italy.

The author helpfully notes Pius’s many early accolades and expressions of gratitude from prominent Jewish leaders, including Albert Einstein and Golda Meir. The testimony of the people with firsthand evidence – Italian Jews who survived – is carefully and persuasively presented. The author also takes note of early and later historical accounts of the period that praise the pope’s efforts to relieve suffering and save lives throughout Nazi-occupied Europe; one Israeli scholar he mentions keeps a folder on his desk under the heading, “Calumnies Against Pius XII.”

What is not in dispute is that 85% of Italy’s Jews survived the Holocaust, many of them hidden in churches, convents, monasteries, at the pope’s palace at Castel Gandolfo, and inside the Vatican itself. What is also not in dispute is that the pope never publicly excommunicated Hitler – a baptized, but apostate, Roman Catholic.

And as is so often the case in historical disputes, the argument remains heated because the stakes remain high. What people think of Good Pius or Bad Pius depends to no small degree on what the disputants think about today’s Catholic Church, today’s papacy, priestly celibacy, women priests, Vatican II, John Paul II, and, perhaps most important, the nature of guilt itself.

Rabbi Dalin is not shy about what he thinks: The Nazis and the people who cooperated with them are to blame for the Holocaust. This includes a huge cast of characters; some professed religion, most did not. He strongly believes that the Hochhuths of the world would like to spread the blame in part to dilute it. Pope Pius XII is certainly not culpable in any way and should be honored rather than defamed for his efforts during the war.

Some of his most devastating evidence for his argument comes from the Nazis themselves, who had referred to Pius as a “Jew-loving cardinal” prior to his accession to the papal throne (possibly because he helped draft his predecessor’s anti-Nazi encyclical, “Mit brennender Sorge” – “With Burning Anxiety”). He also documents Hitler’s aborted plot to kidnap the pope, an odd plan if Pius already “belonged” to him.

On the question of the pope’s much discussed “silence,” the author provides considerable evidence that he spoke up frequently in public and private. If his performance in this area was more restrained than some of his critics, inside and outside the church, would have liked, this might have been prudential judgment. When the Dutch bishops blasted the Nazis for deporting Dutch Jews, the operation became even more savage overnight.

Furthermore, in the long history of popes excommunicating errant rulers there has been only one notable success – bringing Henry IV to Canossa in 1077 – and many failures, the most spectacular being with Elizabeth I of England, who promptly executed hundreds of Roman Catholics and finalized the split from Rome.

This will not, by any means, be the last word on Pius XII. Opponents of Catholic orthodoxy, like the ex-priest James Carroll (author of the papal bashing “Constantine’s Sword”), have too much invested personally and professionally to abandon the fight.

We can only hope that Rabbi Dalin hangs in there, reminding everybody who will listen that real anti-Semitism is very much alive and a deadly threat to us all. As he duly notes, the notorious “Protocols of the Elders of Zion” and “Mein Kampf” are readily and widely available throughout the Middle East.

Mr. Willcox last wrote in these pages on Ronald Reagan.