The Pius War (or Pius Wars) refer to debates over the legacy of Pope Pius XII and his actions during the Holocaust. The phrase was first coined in a 2004 book of the same name.

World War II Pius XII was crowned Pope of the Catholic Church on 2 March 1939, and was thus leader of the Church and the sovereign of Vatican City, which maintained an official policy of neutrality, during all of World War II. During Pius's reign, and for several years after his death in 1958, he was praised by some political leaders, civilians, and members of the press. However, Pius's generalized public statements about genocide while most of Europe's Jews were being killed off never specifically mentioned Jewry and were considered inadequate by the Allies and by the Polish government-in-exile.

1960s In 1963, a play entitled The Deputy which portrayed Pius XII as a sycophantic aide to Hitler, was produced on the German stage. This event began the first serious public discussion of Pius's record."Serious criticism of Pius only began to be aired a generation after the war following the staging of the anti-Pius play “The Deputy” in 1963 (the playwright, Rolf Hochhuth, is a noted friend and defender of Holocaust denier David Irving)."

"Pius Wars" books and articles published during the 1960s include:

The Deputy: A Christian Tragedy” (original title: “Der Stellvertreter. Ein christliches Trauerspiel") signaled the beginnings of the Pius Wars. It was first staged in Germany in 1963, but was subsequently translated into multiple languages, staged in several countries, and given much publicity. Its author, Rolf Hochhuth, also published a book based on the play, which purported to give evidence that his portrayal of the Pope was accurate. The controversy the play raised received much attention for several years, but became muted for a time after Hochhuth published a second play, The Soldiers, also denigrating Winston Churchill, which was roundly condemned.

Irish Catholic journalist Desmond Fisher attempted to rebut Hochhuth's charges in Pope Pius XII and the Jews: An Answer to Hochhuth’s Play, Der Stellvertreter, a pamphlet also published in 1963, when the play was first staged.

An American professor of political science, Guenter Lewy, published The Catholic Church and Nazi Germany in 1964, soon after “The Deputy” was staged but said in his preface that research for the book began in 1960. Lewy relied primarily on “large quantities of German State and Party documents and the opening of some Church archives". He opined that the "often fierce reaction to Hochhuth's play" was due to its having touched a "raw nerve" and says that the relationship between the Catholic Church and Nazi Germany is "a subject which for many years has been obscured by what may justifiably be called an extensive mythology."

Lewy used Nazi Party, German State, and German Catholic diocesan archives that were seized by the Allies to reconstruct Nazi-Vatican relations prior to and during World War II.

In 1965 Carlo Falconi attempted to support Hochhuth's thesis in a more scholarly way, with Il Silenzio di Pio XII. (The Silence of Pius XII, an English translation, was published in 1970.) In 1967, Falconi published The Popes of the Twentieth Century, in which he again criticized Pius for "failing to speak out" – "[Pius XII] was also guilty of inadmissable silence about the millions of civilian victims of Nazism – Jews, Poles, Serbs, Russians, gypsies, and others."

In 1966 Saul Friedländer, an Israeli historian, used primary documents to support Hochhuth's thesis in Pius XII and the Third Reich: A Documentation. (The book was first published in 1964, in Paris, under the title, Pie XII et le IIIe Reich, Documents.) Friedländer suggested the Vatican should open its record archives, and in 1964, Pope Paul VI commissioned a group of Jesuit scholars to edit and publish the Vatican's records. These were published in eleven volumes between 1965 and 1981.

In Three Popes and the Jews, Israeli journalist and former DELASEM member Pinchas Lapide in 1967 defended Pius, claiming that the Pope, through the Catholic hierarchy, was responsible for saving from 700,000 to 860,000 Jewish lives. The passage in his book in which Lapide presents and explains how he arrived at this figure reads as follows. (The passage doesn't include any references or citations.)The Catholic Church, under the pontificate of Pius XII was instrumental in saving at least 700,000, but probably as many as 860,000, Jews from certain death at Nazi hands. (The total number of Jews who survived Hitler in ex-Nazi-occupied Europe, excluding Russia, thanks, in part at least, to Christian help, is approximately 945,000. To these must be added the 85,000-odd whom Christians helped escape during the war to Turkey, Spain, Portugal, Andorra and Latin America. Of the resultant total, exceeding one million Jewish survivors, I deducted all reasonable claims of rescue made by the Protestant Churches - mainly in France, Italy, Hungary, Finland, Denmark and Norway; the Eastern Churches - mainly in Roumania, Bulgaria and Greece - as well as those saved by Communist, self-declared agnostics and other non-Christian Gentiles. The final number of Jewish lives in whose rescue the Catholic Church had been instrumental is thus at least 700,000 souls, but in all probability is much closer to the maximum of 860,000.) In Death in Rome, the first of his books on Pius XII's record in regard to Rome's Jewish population, Robert Katz in 1967 accused the Pope of having had foreknowledge of the Ardeatine Caves massacre.

In Black Sabbath: A Journey Through a Crime Against Humanity, his second book on Pius XII, Katz accused him of failing to protect Rome's Jews, and of having done nothing to prevent the deportation of Jews from the Roman ghetto.

In 1969 University of Lucerne professor of history defended Pius XII's record in Pius XII and Nazi Germany in Historical Perspective (Historical Studies: Papers Read before the Irish Conference of Historians, VII) and in many other writings. He called the attacks on Pius "spurious."

1970s and 1980s

British historian Anthony Rhodes defended both Pius XI and Pius XII in his 1973 book titled The Vatican in the Age of the Dictators, 1922 – 1945, asserting that the Popes' primary concern was pastoral.

According to journalist William Doino, Jr., "By the late 1960s, the attack on Pius XII seemed to have been turned back with the discrediting of The Deputy. One of the few books to appear in the next generation of scholarship was John F. Morley's Vatican Diplomacy and the Jews During the Holocaust, 1939 – 1943. Father Morley's 1980 book was one of the first to take into account the Vatican's Actes et Documents (though his book ends with the events of 1943 and was published before the last two volumes of the Actes were available). Morley used these and other primary Vatican documents to find fault with the Vatican for not confronting the Nazis in regards to the persecution of the Jews. He also blames the Vatican for primarily concentrating on helping Jews who had been baptized into the Catholic Church.

At the end of his book, Morley writes:It must be concluded that Vatican diplomacy failed the Jews during the Holocaust by not doing all that it was possible for it to do on their behalf. It also failed itself because in neglecting the needs of the Jews, and pursuing a goal of reserve rather than humanitarian concern, it betrayed the ideals that it had set for itself. The nuncios, the secretary of state, and, most of all, the Pope share the responsibility for this dual failure.Father Michael O'Carroll used Vatican archival documents, Nuremberg Trial transcripts, and other primary documents to argue against Father Morley's Vatican Diplomacy in another 1980 book, Pius XII: Greatness Dishonored – A Documented Study.

1990s After Father Morley's book and the response to it, the controversy died down until 1997, when ex-priest James Carroll wrote an article for The New Yorker titled The Silence, which once again brought up the question of Pius’s “silence.” The article was followed by a large number of anti-Pius articles and books as well as a flurry of rebuttals. Carroll drew parallels in his article between the reign of Pope John Paul II and that of Pius XII. He claimed that, despite John Paul's attempts, Catholic-Jewish relations would never improve until the Church admitted that Pius XII did wrong in not speaking out against the Nazi regime. The reason, he said, that the Church refused to admit its wrongdoing was that it could not break the tenet of papal infallibility.

A Catholic sister of the order Religious Teachers Filippini, Dr. Margherita Marchione collected oral histories from Italian Jews and Catholics to make the case that in her 1997 Yours Is a Precious Witness: Memoirs of Jews and Catholics in Wartime Italy that "No longer can one speak of [Pius XII's] silence.... His was a language of action.

Father , one of the four Jesuit priests who edited the Vatican's multi-volume Actes et Documents (purporting to contain the Vatican's most salient wartime documents), in 1999 wrote Pius XII and the Second World War According to the Archives of the Vatican to summarize the findings of the Actes. His opinion was that Pius XII would be vindicated once the Vatican Archives were fully opened (which they were in 2020).

In Hitler’s Pope, English journalist and ex-Catholic seminarian John Cornwell made the case that Pius aided Hitler's rise to power by encouraging German Catholic Center Party and German Catholic Bishops to support him. The book was both praised and condemned. Kenneth L. Woodward, then religion editor at Newsweek and later a writer in residence at University of Chicago's Lumen Christi Institute, called the book "a classic example of what happens with an ill-equipped journalist assumes the air of sober scholarship.... Most of his sources are secondary and written by Pacelli's harshest critics. Errors of fact and ignorance of context appear on almost every page.... This is bogus scholarship, filled with nonexistent secrets, aimed to shock." Columbia University History Professor V.R. Berghahn in The New York Times, by contrast, wrote, "By combining the painstaking research of other scholars with his own new documentation on Pius's knowledge and behavior during World War II, John Cornwell, a British journalist and research associate of Jesus College, Cambridge, makes a case in ''Hitler's Pope' that is very difficult to refute." In a 2004 interview, Cornwell said that “Pius XII had so little scope of action that it is impossible to judge the motives for his silence during the war." Four years later, on the other hand, in a new preface to his book, he wrote that "I have found no reason to alter my verdict on Pius XII's scandalous silence on the known facts of the Holocaust in 1942 or his paltry Christmas broadcast of that year, [but] information revealed subsequent to the publication of Hitler's Pope has encouraged me to qualify my opinion on one point regarding Pacelli's inaction following the roundup of Jews from the Roman ghetto in early September 1943. While his failure to act seemed to me undeniably culpable at the time of writing the book, I am now inclined to believe, in the light of new evidence about Hitler's plan to invade the Vatican and kidnap Pius, that the circumstances and the conflicting pressures were sufficiently complex to allow Pacelli a measure of benefit of the doubt." (Other historians have cast substantial doubt on the plausibility of the alleged plot to kidnap Pius.)

2000s Liberal Catholic Garry Wills denigrated Pius XII and other Popes in Papal Sin: Structures of Deceit, a 2000 argument against papal power and in favor of Church reform.