Pope Pius V

When Pius V became pope in 1566, the Council of Trent had closed only three years earlier, leaving its sweeping program of reform still largely unenacted across a Latin Church that had spent decades responding piecemeal to the Protestant Reformation. Pius made implementation his central project. In 1566 he issued the Roman Catechism, a summary of doctrine intended for parish priests rather than scholars, meant to standardize what ordinary Catholics were actually taught at a moment when confessional lines across Europe were hardening. He followed it with a reformed Roman Breviary in 1568, consolidating the daily cycle of psalms, readings and prayers that clergy were bound to recite, and then, in 1570, with the Missal that took his name, an attempt to fix the text and rubrics of the Mass itself into a single authorized form for the whole Latin Church, superseding the patchwork of local uses that had multiplied across the medieval centuries.

The Missal's bull of promulgation, Quo Primum, presented the new text not as one option among several but as binding, with only rites that could show at least two centuries of continuous local use permitted to continue alongside it. That form endured, with revisions, until the Second Vatican Council's Missal of Paul VI replaced it four centuries later in 1970, and it survives today as the Tridentine Mass, the older of the Roman Rite's two authorized forms. Pius's own background as a rigorous Dominican theologian and former head of the Roman Inquisition shaped the reforms' character throughout, favoring uniformity and doctrinal precision over the regional variation the medieval Church had tolerated.

Before his election, Ghislieri had risen through the Dominican order and then the Roman Inquisition, becoming its Grand Inquisitor in 1558 and earning, even among contemporaries who admired his personal austerity, a reputation for severity that followed him into the papacy. As pope he continued to treat doctrinal and political uniformity as inseparable concerns.

In 1570 he issued the bull Regnans in Excelsis, excommunicating Elizabeth I of England, declaring her deposed as a heretic, and releasing her subjects from any obligation of allegiance, a step that hardened rather than improved the position of England's Catholics, who now faced suspicion of disloyalty to the crown on top of religious persecution. His most celebrated achievement came against a different adversary.

Alarmed at Ottoman naval expansion in the Mediterranean, Pius assembled the Holy League, an alliance of Spain, Venice and the Papal States among others, whose combined fleet met and destroyed the main Ottoman fleet at the Battle of Lepanto in October 1571, a victory widely regarded at the time as having checked Ottoman naval power in the western Mediterranean for a generation. Pius attributed the outcome to the intercession of the Virgin Mary, invoked through the rosary devotions he had ordered said across Catholic Europe as the fleets engaged, and instituted a feast, Our Lady of Victory, later folded into the feast of the Holy Rosary, to commemorate it. He died the following year and was canonized in 1712, one of relatively few popes to be recognized as a saint.