The feast was introduced by Pope St. Pius V (1504-1572) in the year 1571 to commemorate the miraculous victory of the Christian forces in the Battle of Lepanto on October 7, 1571. The pope attributed more to the “arms” of the Rosary than the power of cannons and the valor of the soldiers who fought there.
Legend tells us that the Rosary as a form of prayer was given to St. Dominic (1170-1221) by Mary, the Mother of Our Lord, who entrusted it to him as an aid in the conflicts with the Albigensians. The Dominican pope, St. Pius V, did much to further the spread of the Rosary and it thereafter became one of the most popular devotions in Christendom. It was the same Pope St. Pius V, who in 1569 officially approved the Rosary in its present form with the Papal Bull, Consueverunt Romani Pontifices. It had been completed by the addition of the second half of the “Hail Mary” and the “Glory be to the Father” at the conclusion of each mystery.