Saint Pius V gave Mary the title: "Help of Christians," after the victory of the Christian fleet over the Turks at Lepanto on October 7, 1571, and he added this invocation to her litany. When Pius VII returned to Rome on May 24, 1814, after spending five years of exile and captivity, he established the Feast of Our Lady, Helper of the Papal States.   The invocation of Mary as Help of Christians is part of the oldest prayer addressed directly to Mary, the "Sub tuum praesidium," which was found on a papyrus dating, at the latest, from the end of the third century. This prayer was composed at a time of great danger for Christians and for the Church. "Praesidium" is translated as "an assistance given in time of war by fresh troops in a strong manner."

Prayer to Our Lady, Help of Christians
Mary, powerful Virgin, You are the mighty and glorious protector of the Church. You are the marvelous help of Christians. You are awe inspiring as an army in battle array. In the midst of our anguish, struggle, and distress, defend us from the power of the enemy, and at the hour of hour death, receive our soul in Heaven. Amen