Saint Leo the Great was born in Rome. He received a great education, which opened many paths for him to pursue a very good secular career. However, he desired more of a spiritual life and became an archdeacon of pope Sixtus III. After Sixtus' death, Leo was elected the pope of Church in Rome in September 440.
It was a challenging time for the Church, when heretics assaulted Orthodoxy with their false teachings. Leo knew how to combine pastoral solicitude and goodness, while remaining steadfast in his confession of the true Faith. It was Leo who became the main defender of the Faith against the heresies of Eutyches and Dioscorus, who taught that there was only one nature in the Lord Jesus Christ.
He was able to bring to the Church, which was troubled by the heresies, to peace. Through his letters to emperor Theodosius and Marcian, Leo was able to convince them to convene Fourth Ecumenical Council in Chalcedon in 451 to condemn the heresy of Eutyches and Dioscorus. 630 bishops attended the Council, however, Leo was not one of them. But his letter to the patriarch of Constantinople Flavian was read before all those gathered.
In the letter, Leo presented the Orthodox teaching about the two natures [the divine and the human] in the Lord Jesus Christ. All the bishops of the Council were in agreement with this teaching, and so the heretics Eutyches and Dioscorus were excommunicated from the Church.
Leo was also the defender of his native land from the invasion of the barbarians. In 452 he was able to persuade Attila the Hun from ravaging Italy. And in 455, when the leader of the Vandals (a Germanic tribe), Henzerich, set his sights on Rome, Leo talked him out of destroying the city.
St Leo lived to old age. He knew the time of his death beforehand, and prepared himself, with forty days of fasting and prayer, to pass from this world into eternity. He died in 461 and was buried in Rome. His literary and theological legacy consists of 96 sermons and 143 letters, of which the best known is his Epistle to Saint Flavian.
You were the Church’s instrument in strengthening the teaching of true doctrine; you shone forth from the West like a sun dispelling the errors of the heretics. O righteous Leo, entreat Christ God to grant us His great mercy.
Seated upon the throne of the priesthood, O glorious Leo, you shut the mouths of the spiritual lions. With divinely inspired teachings of the honored Trinity, you shed the light of the knowledge of God upon your flock. Therefore, you are glorified as a divine initiate of the grace of God.
May the example of St Leo inspire us to be faithful defenders of Christianity and of our homeland. Notice that St Leo did not use violence, even when trying to negotiate with barbarians. He put his trust in the Lord and faced the danger as a mere mortal. In the same way, when defending the Faith from the heresies, he did not get personal and offensive. His great knowledge and strong faith helped him. Therefore, do not argue over things you don't know. And learn the Orthodox Christian faith because you never know when you might be tested to defend it.
Through the prayers of Saint Leo, O Lord Jesus Christ our God, have mercy on us. Amen.
Yours in Christ,