Leo I., saint, surnamed the Great; was distinguished for his zeal against heretics, presided at two councils, and persuaded Attila to retire from Rome on his invasion of Italy, as he persuaded Genseric four years later to moderate the outrages of his troops in the city; his letters are in evidence of the jurisdiction of the Roman over the universal Church. Festival, Nov. 10.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Leo * Leo III.