St. Pius V, who was born in 1504, joined the Dominicans at the age of fourteen; he was sixty-two when he was elected Pope.
His reign, though short, was one of the most fruitful of the sixteenth century. To Protestantism, which had proclaimed the Reformation, St. Pius replied by applying the decrees of the Council of Trent for the reform of the Church. He played a great part in the return of the clergy to ecclesiastical discipline. We also owe to St. Pius the reformation of the liturgical books of the Roman rite.
Against Islam, which threatened the West, he succeeded in forming a coalition of Christian forces: and by public prayers, organized everywhere at his request, he was instrumental in obtaining the decisive victory of Lepanto in 1571. He died the following year on May 1.