Who he was
Leo, a Tuscan, son of Quintianus according to the Liber Pontificalis, was already well known as a deacon of Rome under Celestine I. He was in Gaul on a peace mission for the emperor when Sixtus III died, and was chosen to succeed him; he was consecrated on 29 September 440 and reigned for twenty-one years as the Western Empire crumbled.
What he is remembered for
His great letter to Flavian of Constantinople, written against the error of Eutyches, set out the Church's faith in the Person of Christ and was accepted by the Council of Chalcedon in 451. In 452 he met Attila the Hun near Mantua and persuaded him to withdraw from Italy, and in 455 he won from the Vandal Genseric a promise to spare the lives of the people of Rome. Ninety-six of his sermons survive, and in 1754 Benedict XIV declared him a Doctor of the Church.
He is honoured by the Church as Saint. Read his page in the dictionary of saints.
Sources
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