27th October 312: Constantine the Great receives his Vision of the Cross that starts his conversion

Constantine was one of the co-emperors of the Tetrarchy who were engaged in civil wars for dominance of the Roman Empire. By 312 he and Maxentius, who was treated as a usurper by the senior emperor Galerius, were engaged in open hostility with one another. Constantine’s 40,000 troops had managed to dominate northern Italy, and on 27 October were encamped near the Milvian Bridge over the River Tiber outside Rome.

While the exact details vary in historical accounts, the core narrative of what happened that evening remains consistent. While preparing for the decisive battle against his rival, Constantine reportedly witnessed a Christian cross which may have been accompanied by a Latin inscription which roughly translates as ‘In this sign, you will conquer.’ This vision is often referred to as the ‘Vision of the Cross’ and had a profound impact on Constantine.

The popular account says that Constantine interpreted the vision as a divine message, and ordered his soldiers to paint their shields with the Christian Chi-Rho symbol. This monogram combines the Greek letters for ‘Χ’ (Chi) and ‘Ρ’ (Rho), to represent the Greek word Christos, or Christ.

The Battle of the Milvian Bridge was fought the next day. Constantine’s forces secured a decisive victory and Maxentius perished, giving Constantine undisputed control of the western half of the Roman Empire. His conversion to Christianity marked a turning point in the history of the Roman Empire and played a vital role in the faith’s rise to prominence.