Leo I
391 — 461
A Roman aristocrat who became Pope in 440 while on a diplomatic mission to Gaul, Leo shaped the theology and authority of the Roman see more than any pope before him. He wrote the Tome to Flavian in 449, whose definition of Christ's two natures in one person was acclaimed at the Council of Chalcedon. In 452 he rode out to the Mincio River to meet Attila the Hun, who turned back without sacking Rome — an outcome historians debate but tradition credits to Leo's personal authority.