Constantine the Great

Constantine I (27 February 272 – 22 May 337), known as Constantine the Great, ruled as Roman emperor from 306 to 337 and was the first to embrace Christianity. He significantly boosted Christianity’s standing in the empire; the Edict of Milan ended the persecution of Christians and made the faith legal, marking a crucial shift toward the Christianisation of Rome. He also established Constantinople (modern-day Istanbul) as the empire’s new capital, a role it held for over a thousand years.

Born in Naissus (in present-day Niš, Serbia), Constantine was the son of Flavius Constantius, a Roman officer from the same region who later became one of the Tetrarchy’s four emperors. His mother, Helena, was a Greek woman of humble origins, likely from Bithynia. Later canonised, she is sometimes credited with converting her son, though other accounts say Constantine converted her. He served with distinction under emperors Diocletian and Galerius, first campaigning in the east against the Persians, then being recalled west in 305 to fight alongside his father in Britannia. When his father died in 306, Constantine’s army proclaimed him augustus at Eboracum (York, England). He eventually defeated rivals Maxentius and Licinius in the civil wars of the Tetrarchy, becoming sole ruler by 324.

As emperor, Constantine introduced wide-ranging reforms. He restructured government, separating civil and military authority. To curb inflation, he created the solidus, a gold coin that became the standard for Byzantine and European currencies for over a millennium. He disbanded the Praetorian Guard, which had backed Maxentius. The army was reorganised into mobile units, often stationed near the emperor for campaigns against external enemies or rebels, and frontier garrison troops, capable of handling barbarian raids but less effective against full-scale invasions. He campaigned against tribes like the Franks, Alemanni, Goths, and Sarmatians, and repopulated territories abandoned during the Crisis of the Third Century with Roman citizens.

Though Constantine lived much of his life as a pagan, he became a catechumen after favouring Christianity from 312 onward, and was eventually baptised by Eusebius of Nicomedia, an Arian bishop. He helped issue the Edict of Milan in 313, legalising Christianity. He convened the First Council of Nicaea in 325, which produced the Nicene Creed. On his orders, the Church of the Holy Sepulchre was built on the site believed to be Jesus’s tomb in Jerusalem, becoming Christendom’s holiest site. Often called the “First Christian Emperor,” he certainly favoured the Church, though modern scholars debate his personal beliefs and understanding of Christianity. He is venerated as a saint in Eastern Christianity and parts of Western Christianity, and he did much to integrate Christianity into mainstream Roman culture.

Constantine’s reign marked a distinct era in Roman history and a pivotal shift from classical antiquity to the Middle Ages. He built a new imperial residence at Byzantium, officially named New Rome but soon called Constantinople in his honour. It remained the empire’s capital for over a thousand years—the Eastern Roman Empire later being retrospectively termed the Byzantine Empire. By leaving the empire to his sons and other members of the Constantinian dynasty, he replaced Diocletian’s Tetrarchy with dynastic succession. His memory was highly esteemed during his children’s lifetimes and for centuries after. The medieval church saw him as a model of virtue, while secular rulers invoked him as a symbol of legitimate rule. The rediscovery of critical sources in the early Renaissance led to more balanced appraisals, and modern scholarship often tries to navigate between earlier extremes.

Sources about Constantine are abundant but controversial. No contemporary histories or biographies survive; the closest is Eusebius’s *Vita Constantini*, a eulogy and hagiography written between 335 and 339 to praise Constantine’s moral and religious virtues. Its reliability is often questioned. The anonymous *Origo Constantini* offers a secular account focused on military and political events, neglecting cultural and religious matters. Lactantius’s *De mortibus persecutorum* provides valuable but biased detail on Constantine’s predecessors and early life. The ecclesiastical histories of Socrates, Sozomen, and Theodoret, written a century later under Theodosius II, describe the church disputes of Constantine’s later reign.