By 1571 the Ottoman Empire under Sultan Selim II had taken Cyprus and stood at the threshold of Italy. Pope St. Pius V — himself a Dominican, an order founded on the preaching of the Rosary — assembled a fragile Holy League of Spain, Venice, the Papal States, Genoa, Malta, and several smaller Italian states. He called for Rosary processions in every parish of Christendom on the day of battle and asked the confraternities of the Rosary to pray without ceasing.
On October 7, 1571, the Holy League fleet of some 200 galleys, commanded by Don John of Austria, met the larger Ottoman fleet of roughly 270 ships in the Gulf of Patras off Lepanto, in western Greece. Against every expectation, the Holy League won decisively, sinking or capturing about 200 Ottoman vessels and freeing approximately 12,000 Christian galley-slaves.
Pope Pius V, then in Rome and several hundred miles from the battle, is said to have suddenly stopped a meeting with cardinals, walked to the window, and announced: 'It is not the time for business; let us go and thank God for the victory He has just given to the Christian arms.' Word of the actual battle did not reach Rome for two weeks.
In thanksgiving, Pius V instituted the feast of Our Lady of Victory, soon renamed Our Lady of the Rosary, which the Church still celebrates on October 7.