There have been thirteen Popes named Leo; five of them are canonized saints: Saint Leo I, Saint Leo II, Saint Leo III, Saint Leo IV and Saint Leo IX. Saint Leo I, called Saint Leo the Great, was a Pope and Doctor of the Church. He reigned for twenty-one years and fought all manner of heretics. He was “the soul of the Council of Chalcedon,” in 451, which condemned the Monophysites, those heretics who held that the human nature of Jesus was absorbed into the Divine, and no longer exists. This heresy would leave Mary, the Mother of God, without a Child. Saint Leo the Great, by his personal power and fearlessness, kept Attila and the Huns from invading the city of Rome in the year 452.