The Battle of Lepanto was a famous naval victory. On October 7, 1571, the Turks (or Moslems) attempted to invade Christian Europe. The site of the invasion was Lepanto, on the coast of Greece. The Pope asked Catholics to pray the rosary with the intent that the Turks would be defeated.
Though the Christians were outnumber 3-to-1, the Christians were victorious. Estimates vary as to the loses, but they were significant to the Ottomans.There is a feast to Our Lady of the Rosary that is celebrated on October 7th in remembrance of this victory.
Prior to the actual date of the battle, on September 17, 1569, Pope Pius V asked that all Christendom, all the towns and villages, recite the rosary. He requested 40 hours of devotions. On October 7, 1571, like our Lord Jesus, he spent the whole night in prayer.
Later, the Venetian Senate stated, “It was not generals nor battalions nor arms that brought us victory; but it was Our Lady of the Rosary.”
Don John of Austria led the fleet of the Holy League of Europe. This was the Christian fleet that met the Ottoman naval force off of western Greece. Over 100,000 men and over 400 ships were involved in the battle.
Along with massive losses of ships and men on the Ottoman side, 15,000 Christian slaves who used to row Ottoman ships were freed.
Convinced that Europe had been saved from an Islamic invasion, Pope Pius V instituted the Feast of Our Lady of the Rosary (originally known as the Feast of Our Lady of Victory). Initially, this was a local feast. In 1671, this was celebrated in all of Spain.