Leo I the Great

Saint Leo I the Great was Pope from 440 to 461. His pontificate was of paramount importance for the Church and the Roman Empire. He is best known for his decisive role in asserting papal primacy, notably through his doctrine of the 'vicars of Peter'. He actively combated the heresies of his time, such as Monophysitism and Pelagianism, and his 'Tomus ad Flavianum' (Letter to Flavian) was a key document for the Council of Chalcedon (451), defining the doctrine of the two natures of Christ. He is also famous for meeting Attila the Hun in 452, dissuading him from sacking Rome, and for negotiating with Genseric, King of the Vandals, in 455, limiting the destruction of the city. He was proclaimed a Doctor of the Church in 1754.