Today is the memorial of Pope St. Leo the Great, who reigned 440-461 A.D. Those years were, in the words of the Chinese curse, interesting times.

Within the Church, Leo is best known for his great Tome, the letter that served as a summary of christological doctrine — the final punctuation mark on a century of disputes over Jesus’ person and nature(s). The Tome was accepted and ratified by the Council of Chalcedon in 451. But Leo makes the secular history books because he was able to reach peace with a seemingly implacable military power — and, in doing so, he stanched the flow of blood that had soaked the lands and swelled rivers all across the Europe.

By the year 440, the Empire in the West was a mess. The Emperor might pretend to rule, but except in Italy itself the real rulers were the barbarians who had conquered most of the provinces.

And the city of Rome itself, once mistress of the world, was no longer even mistress of the tattered remnant of the Empire. The capital of the West had moved to Ravenna, a city protected on one side by the sea and on the other sides by swamps. The Emperor could be safe there, even if his people weren’t safe in the rest of Italy. Meanwhile, as Rome and the West decayed into anarchy and poverty, Constantinople and the East continued to prosper.

Where did that leave the pope? When Rome ruled the world, it seemed natural enough that the bishop of Rome should rule the Church. And the see of Rome had been founded by Peter, the chief of the Apostles. But now Rome was a backwater compared to Constantinople, and the bishop of Antioch might fairly point out that Peter had founded his see, too. How could the bishop of Rome claim authority over the whole Church?

Just as the question was beginning to seem most urgent, a pope came along who had exactly the right answer. His name was Leo, and history remembers him as Leo the Great. Leo’s answer was that the pope held his authority as the heir of Peter. Christ had given Peter authority over the other disciples, and the bishop of Rome inherits that authority over the other bishops.

In Roman law, an heir took on all the rights and duties of the deceased. So Peter, the holder of the keys to heaven and the power of binding and loosing, would pass those powers on to his heir, his successor as bishop of Rome; and that successor would pass them on to his heir, and so on down the line. That gave Rome the important edge over Antioch. It was true that Peter had founded both sees. But he had died at Rome, and that made the Bishop of Rome his heir.

Leo was not inventing this inheritance, but explaining it. It is implicit in the appeals of many Fathers to the judgment of the papacy: St. Athanasius, St. Basil of Caesarea, St. Jerome, St. John Chrysostom, St. Augustine, St. Cyril of Alexandria … Theodoret of Cyr put it eloquently: “If Paul, the herald of the Truth, the trumpet of the Holy Ghost, had recourse to the great Peter, in order to obtain a decision from him for those at Antioch who were disputing about living by the Law, much more do we small and humble folk run to the Apostolic See to get healing from you for the sores of the churches. For it is fitting that you should in all things have the pre-eminence, seeing that your See possesses many peculiar privileges.”

Now, in the mid-fifth century, during the reign of Peter’s forty-forth successor, a new horde of barbarians had appeared from the east. The Huns were more terrible than any of the tribes who had come before them. Their chief, Attila, was cruel and brilliant, a master of strategy and one of the most successful generals in history. He built an empire that stretched across Asia and into Europe. He had already ransomed and plundered the eastern provinces of the Roman Empire; now he headed for what was left of the West. At least half a million assorted barbarians came with him. The destruction they left was so complete that the Romans started to call Attila the “Scourge of God.”

In 451, the Huns entered Gaul and did their usual pillaging there. But just as Attila was about to take the city of Orleans, an enormous army of Romans and Visigoths fell on him from behind, taking the Huns completely by surprise. For perhaps the first time, Attila was forced to retreat. But the allied army caught up with him in Champagne, and a terrific battle followed in which more than three hundred thousand men died. It was perhaps the greatest clash of armies Europe had ever seen. (Reliable historians say that a small neighboring stream was swelled to a raging river by the blood spilled on the field.) Attila was defeated and forced to abandon the province.

A year later, in 452, Attila was ready for revenge. This time he swept into Italy. It seemed as though nothing could stop him. The marauding Huns completely depopulated whole sections of Italy. Cities were wiped off the earth, their populations dead or enslaved. With terrifying speed the Huns were approaching Rome itself. The useless Emperor Valentinian was about to abandon all Italy to its fate. Could anyone save Rome from total destruction?

It was time for Pope Leo to step in. If armies could not stop the Huns, then only a greater power would do. Trusting in the protection of God, Pope Leo set out without an army to face the Scourge of God.

Everyone was surprised when Attila received the Pope with honor and hospitality. Something about the great Pope Leo impressed even the unstoppable conqueror. By the time the Pope was through conferring with him, Attila had agreed to leave Italy and make peace with the Empire, in return for an annual tribute. Thus Pope Leo, alone and undefended, accomplished what the best Roman generals and their hundreds of thousands of soldiers hadn’t been able to do. Attila turned around and marched back across the Alps, headed back for his own empire.

He never made it. On the way home, he fell violently ill and died. His empire almost immediately fell apart, with his sons and vassals fighting bloody civil wars.

In spite of all the chaos in the Western Empire, the emperors continued to murder each other on a regular schedule caring more for their own fleeting power than for the safety of the Empire. Maximus murdered Valentinian, and Valentinian’s widow was so distraught that she invited the Vandals, who by now had settled in Africa, to come and avenge the murder. The Vandals took the opportunity to pillage Rome in 455. Pope Leo could do nothing to stop them, but he did at least manage to persuade them not to kill the inhabitants and burn down the buildings.

Leo possessed great power when he ruled on earth. Yet he holds greater power today, as he intercedes before the throne of the Almighty. St. Leo, pope and peacemaker, pray for us, who live in interesting times, and violent times.