Pope Leo I

Pope Leo I, also known as Leo the Great, was a Roman aristocrat who served as bishop of Rome from 29 September 440 until his death on 10 November 461. During his reign he contributed significantly to developing ideas of papal authority, founded upon the apostolic succession of the Bishop of Rome from Saint Peter. He is perhaps best known for meeting Attila the Hun in 452 and persuading him to turn back from his invasion of Italy, though scholars debate how large a part his personal authority played. He is also known for his role at the Council of Chalcedon, where he issued the Tome of Leo setting out the hypostatic union of Christ's two natures, divine and human, in one person; for this he was later named a Doctor of the Church.