In 1531 the Blessed Virgin Mary appeared to St. Juan Diego, and her image became miraculously imprinted on his tilma, a cloak of cactus fiber. She revealed herself as Our Lady of Guadalupe and devotion to her spread throughout South America, as well as in Europe.
According to Brother John M. Samaha for the University of Dayton, "Throughout Europe copies of the holy image had been circulated. One of the first copies was given to Admiral Giovanni Andrea Doria, grandnephew of the renowned Admiral Andrea Doria. The young admiral took the picture aboard his flagship when he assumed command of a flotilla of ships sailing from Genoa to the Gulf of Lepanto."
The Battle of Lepanto was fought on October 7, 1571, and it is said that during the battle, "Doria went to his cabin and knelt in prayer before the image of Our Lady of Guadalupe."
Prior to the battle, Pope Pius V had encouraged everyone to pray the Rosary, and many of the sailors prayed the Rosary the night before.
Miraculously, the Christian fleet was victorious and many believed it was due to the protection of the Virgin Mary.