In December of 1565, Pope Pius IV died, his one monumental achievement the resumption and successful conclusion of the Council of Trent. The man chosen to succeed Pius IV and upon whose shoulders rested the responsibility for carrying out the decrees of the council was Michael Ghislieri, a Dominican friar. It was the late pontiff's nephew St. Charles Borromeo who had been the driving force in the election of the new pope, for he recognized that a remarkable leader would be needed if the decrees of the council were to bear fruit.
Michael Ghislieri was a poor shepherd boy who entered the Dominicans at the age of fourteen, became a lecturer in philosophy and theology at Pavia, and very early became involved in the reform movement in the Church. His reforming labors brought him to the attention of other members of the reform movement, and he was given important positions in Como, Bergamo, and Rome. In 1556, he was consecrated bishop of Sutri and Nepi, and then to the diocese of Mondevi, lately ravaged by war. In a very short time, the diocese was flourishing and prosperous. His views on reform were often asked by the Holy Father, and he was noted for his boldness in expressing his views.
His holiness and austerity of life were notable, and he succeeded in bringing simplicity even into the papal household. He refused to wear the flowing garments of previous popes and insisted upon wearing his white Dominican habit even as head of the Church. To this day, the pope wears white, a custom begun by this Dominican pontiff.
The announced intention of St. Pius V was the carrying out of the decrees of the Council of Trent. He insisted that bishops reside in their diocese under pain of losing their revenues; he made a systematic reform of religious orders, established seminaries, held diocesan synods, and reformed the Breviary and Missal. He brought unity into divine worship, published catechisms, ordered a revision of the Latin Vulgate and revitalized the study of theology and canon law. During his pontificate, the Turks were definitively defeated at the battle of Lepanto, due, it was said, to the prayers of the pope.
Pius V died in 1572, at the age of sixty-eight, deeply grieved by the troubles besieging the whole Church. He was canonized by Pope Clement XI in 1712.
~from Catholic Culture