While serving as archdeacon under Pope Celestine I, Leo was already recognized as a skilled man in Church affairs. He was elected pope in the year 440 and governed the Roman See for twenty-one years. His long pontificate was marked by political wisdom, strong relations with the Eastern Churches, clear and mature judgment in matters of faith and discipline, his role in shaping the Church’s worship, and his gifts as a preacher. All of this makes Leo I the most important Roman pontiff of the fifth century.
His teaching on the two natures of Jesus Christ was decisive at the Council of Chalcedon. Attila, king of the Huns, felt honored when the pope himself came to meet him at Mantua and persuaded him to withdraw his army. Leo was not so fortunate, however, with Genseric the Vandal.
The pope died on November 10, 461. This is also the date recorded in the Hieronymian Martyrology. In earlier times Rome celebrated his feast on June 28, because on that day in the year 688 Pope Sergius I had his body moved from the atrium into the interior of Saint Peter’s Basilica. Martyrologies from the eighth century placed his feast on April 11, and this remained the date in the Roman liturgy from the twelfth century until the most recent reform of the calendar. The Eastern Churches celebrate him on February 17 (or 18).
