Humanities › History & Culture Who Was Constantine the Great? His legacy included spreading Christianity throughout the Roman Empire Share Flipboard Email Print Constantine. Hulton Archive/Getty Images History & Culture Ancient History and Culture Rome Figures & Events Ancient Languages Greece Egypt Asia Mythology & Religion American History African American History African History Asian History European History Genealogy Inventions Latin American History Medieval & Renaissance History Military History The 20th Century Women's History View More By N.S. Gill Ancient History and Latin Expert M.A., Linguistics, University of Minnesota B.A., Latin, University of Minnesota N.S. Gill is a Latinist, writer, and teacher of ancient history and Latin. She has been featured by NPR and National Geographic for her ancient history expertise. our editorial process N.S. Gill Updated August 10, 2018 The Roman Emperor Constantine (c 280 - 337 A.D.) was one of the most influential personages in ancient history. By adopting Christianity as the religion of the vast Roman Empire, he elevated a once illegal cult to the law of the land. At the Council of Nicea, Constantine the Great settled Christian doctrine for the ages. And by establishing a capital at Byzantium, which became Constantinople and then Istanbul, he set into motion events that would break the empire, split the Christian church, and influence European history for a millennium. Early Life Flavius Valerius Constantinus was born in Naissus, in the province of Moesia Superior, present-day Serbia. Constantine's mother, Helena, was a barmaid and his father a military officer named Constantius. His father would rise to become the Emperor Constantius I and Constantine's mother would be canonized as St. Helena, who was thought to have found a portion of Jesus' cross. By the time Constantius became governor of Dalmatia, he required a wife of pedigree and found one in Theodora, a daughter of Emperor Maximian. Constantine and Helena were shuffled off to the eastern emperor, Diocletian, in Nicomedia. The Fight to Become Emperor Upon his father's death on July 25, 306 A.D., Constantine's troops proclaimed him Caesar. Constantine wasn't the only claimant. In 285, Emperor Diocletian had established the Tetrarchy, which gave four men rule over a quadrant each of the Roman Empire, with two senior emperors and two non-hereditary juniors. Constantius had been one of the senior emperors. Constantine's most powerful rivals for his father's position were Maximian and his son, Maxentius, who had assumed power in Italy, controlling Africa, Sardinia, and Corsica as well. Constantine raised an army from Britain that included Germans and Celts, which the Byzantine historian Zosimus said included 90,000 foot soldiers and 8,000 cavalry. Maxentius raised an army of 170,000 foot soldiers and 18,000 horsemen. On October 28, 312, Constantine marched on Rome and met Maxentius at the Milvian Bridge. The story goes that Constantine had a vision of the words in hoc signo vinces ("in this sign you will conquer") upon a cross, and he swore that, should he triumph against great odds, he would pledge himself to Christianity. (Constantine actually resisted baptism until he was on his deathbed.) Wearing a sign of a cross, Constantine won, and the following year he made Christianity legal throughout the Empire with the Edict of Milan. After Maxentius' defeat, Constantine and his brother-in-law, Licinius, split the empire between them. Constantine ruled the West, Licinius the East. The two remained rivals over a decade of uneasy truces before their animosity culminated in the Battle of Chrysopolis, in 324. Licinius was routed and Constantine became sole Emperor of Rome. To celebrate his victory, Constantine created Constantinople on the site of Byzantium, which had been Licinius' stronghold. He enlarged the city, adding fortifications, a vast hippodrome for chariot racing, and a number of temples. He also established a second Senate. When Rome fell, Constantinople became the de facto seat of the empire. Death of Constantine By 336, Constantine the Great had reclaimed most of the province of Dacia, lost to Rome in 271. He planned a great campaign against the Sassanid rulers of Persia but fell ill in 337. Unable to complete his dream of being baptized in the Jordan River, as was Jesus, he was baptized by Eusebius of Nicomedia on his deathbed. He had ruled for 31 years, longer than any emperor since Augustus. Constantine and Christianity Much controversy exists over the relationship between Constantine and Christianity. Some historians argue that he was never a Christian, but rather an opportunist; others maintain that he was a Christian before the death of his father. But his work for the faith of Jesus was enduring. The Church of the Holy Sepulchre in Jerusalem was built on his orders and became the holiest site in Christendom. For centuries, Catholic popes traced their power to a decree called the Donation of Constantine (later proved a forgery). Eastern Orthodox Christians, Anglicans, and Byzantine Catholics venerate him as a saint. His convocation of the First Council at Nicea produced the Nicene Creed, an article of faith among Christians worldwide.