Certain to reopen the debate on the political, diplomatic, and, most importantly, moral failure of the Catholic Church in the face of fascism and the Holocaust. Historians have long known that Pius XI--who had sought accommodation with Mussolini's regime in 1929 hut later became convinced that diplomatic methods were futile with both Nazi Germany and Fascist Italy--commissioned an encyclical in June 1938 that was to have been a detailed condemnation of fascism, racism, and anti-Semitism. But Pius XI died in early 1939. His successor was Eugenio Pacelli, the late pope's secretary of state and former papal nuncio in Nazi Germany, who took the name Plus XII. Pacelli was a fanatical anti-communist, convinced that Europe would fare better under Nazi domination than Soviet hegemony. Pius XII never spoke out publicly against Nazi atrocities, not even when the Jews of Rome were rounded up by the SS. The encyclical (titled ""The Unity of the Human Race"") disappeared into the Vatican archives, never to be published. For decades, the Vatican even denied its existence, until it was discovered by a Jesuit seminarian in the late 1960s. Passelecq (a Belgian monk and former member of the anti-fascist Resistance) and historian Suchecky accurately re-create the historical context of the document and trace its fate. Of immense value to historians is the text (over 100 pages) of the encyclical, published in its entirety for the first time in English. It is an extraordinary work, combining a traditional and conservative defense of the family and the faith, along with a detailed critique of modernism and the atomization of contemporary civilization. It insists that the plurality of human ideas and beliefs does not deny an unassailable truth--the unity of the human race. Garry Wills contributes a foreword to this work, which, at a time when the Catholic Church is considering the canonization of Plus XII, may force Catholics and others to reassess his moral failure in a time of crisis.