Truly is St. Leo remembered as "the Great," for we remember him for his work as the Bishop of Rome, turning aside the invading forces of Attila the Hun, and, also by sparing the city greater damage by his intervention with Genseric, king of the Vandals; but even greater work did he do in defense of the Faith of Christ's Church. He withstood the heresies of Nestorius, Eutyches, Appolinarius, and the Manicheans, holding forth the true faith, the faith once-for-all delivered to the saints. 2 Timothy 4:1