From this holy devotion of the Rosary countless benefits have been showered the length and breadth of Christendom. Among these most certainly can be reckoned that famous victory which the Christian princes, aroused by the plea of Pope St Pius V, won over the vastly superior power of the Turks at Lepanto.
THE VICTORY OF LEPANTO
As this victory was won on the very day on which the confraternities of the most holy Rosary throughout the world were offering up their rosaries, as they had been asked to do, there can be no doubt that this victory was an answer to their prayers.
So convinced of this was Gregory XIII that he proclaimed that for so singular a blessing there should be offered everywhere on earth perpetual thanks to the blessed Virgin, under the title of the Rosary. He decreed also that in every church where an altar of the Rosary had been erected, its office should be celebrated in perpetuity under the rite of a double major. Other pontiffs also have granted almost innumerable indulgences to the recitation of the Rosary and to Rosary Confraternities.
– From: An Approved English Translation of the Breviarium Romanum, Burns & Oates, London, 1964