Reigned from 847 to 855. Born and died in Rome. A cardinal-priest. As pope he fortified Rome against the Saracens, enclosed the Vatican Hill with a wall (called after him the Leonine City), and rebuilt Saint Peter's after the Saracen raid of 846. In an important synod, held at Rome (835) various decrees were passed to further ecclesiastical discipline and learning. He rebuked Saint Ignatius of Constantinople for deposing bishops without his knowledge. He crowned Louis II joint Emperor with his father, Lothair I in 850; and Alfred, King of England in 853. Feast, Roman Calendar, July 17,.