Mention is often made of Leo XIII and a famous vision that he saw – that of an attack being made or planned by the devil against the Church. The facts about this vision, however, have been unclear for many decades, for there are different versions of what occurred, and of what was or was not said in that vision. What is fact and what is fiction about this event in modern papal history? To provide clarity about Pope Leo’s vision, Kevin J. Symonds began a historical investigation to arrive at the facts, and to distinguish between rumor or hearsay and the authentic history of the event, as well as to explain its meaning for our time in the light of the teaching of the Church, and in particular of the contemporary Popes. Related to this vision is the well known Prayer to St. Michael and a special prayer of Exorcism. What became known as the Leonine Prayers began to be recited after Masses throughout the world, taking their name from Leo XIII, but their origin came from his predecessor, Blessed Pius IX. Moving into the twentieth century, the author then examines the relationship between Pope Leo’s vision and Fatima, and the decision of Pius XI, after the Vatican’s reconciliation with the Italian government, to continue the Leonine Prayers while adding the conversion of Russia as their intention. Still, the author’s research does not end there, because the events of the second half of the twentieth century have raised even more questions regarding the assaults of the devil, the importance of the message of Fatima, and the tragedy of what Pope Paul VI called the “smoke of Satan” entering the Church. The account goes all the way to the most recent Popes, who were instrumental in the dedication of a new statue of St. Michael inside the Vatican.