The Second Vatican Council represents a departure from tradition so severe that Yves Congar, an influential figure among the architects of the revolt, once boastfully described it thus: "The Church has had, peacefully, its October Revolution." In addition to being an assault against tradition in the most general sense, however, Vatican II was also in many ways an offensive against the legacy of Pope Pius XI in particular, beginning with the events leading up to its calling. Writing in the inaugural encyclical of his pontificate, Ubi Arcano Dei Consilio, Pope Pius XI touched briefly on the possibility of reconvening the...