The Victory at Lepanto
Before the decisive battle between the Christian coalition and the Ottoman Empire, Pope Pius V called all of Europe to prayer.
The Holy League — the Papal States, Spain, Venice, Genoa and the Knights of Malta — was an alliance of powers that had spent the preceding decades at odds with one another. The Pope asked that, while the fleets sailed, churches across Europe keep the Rosary and that the faithful fast and pray for the outcome.
The victory at Lepanto on 7 October 1571 halted the Ottoman advance into the Mediterranean heart of Europe and was widely perceived as an answer to the united prayers of Christians across the continent. The date was afterwards kept as a day of thanksgiving, and the memory of a Europe that prayed together before it acted together outlived the alliance itself.