Pope Leo I was the bishop of Rome from 440 to 461. He is remembered as one of the greatest popes in the history of the papacy. Born in Tuscany, Western Roman Empire, he grew up in an aristocratic Roman family. Not much information is available about his early life. He served as the archdeacon of the ‘Roman Church’ under Pope Celestine I. Leo had also earned respect from the emperor Valentinian III, who often relied on Leo to settle his political disputes. Pope Sixtus III passed away in 440. Soon after that, Leo was elected as the new pope by a unanimous decision. He was immensely respected. Thus, his election as the pope was not debated. He immediately devoted himself to the service of God and worked hard to call out the heresies that were flourishing under his reign, such as Pelagianism and Manichaeism. He also addressed the issue of Jesus Christ’s existence as both divine and human. He wrote a letter that proclaimed that Jesus was a combined form of humanity and spirituality. This reunited the opposing Christian sects. He was also instrumental in bringing about peace between Rome and Attila the Hun. About 100 of his sermons and 150 letters have been preserved to this day.