Can a Battle Standard Change a Religion? One Emperor Said So

The standard was a military one in form, consisting of a long spear crossed by a horizontal bar from which hung a rich cloth banner, with a wreath at the top enclosing a monogram formed from the first two letters of the Greek word for Christ, which combine into a shape resembling a capital P superimposed on an X. Portraits of the emperor and his sons were attached below. It was carried by a dedicated detachment and functioned exactly as other Roman standards did, as a rallying point, a mark of the unit and an object of reverence, with the religious content substituted rather than added.

Two contemporary accounts differ in ways that matter:

• •Lactantius, writing soon after, describes a dream the night before battle
• •In that version Constantine marks a sign on his soldiers' shields
• •Eusebius, writing decades later, describes a vision in the sky
• •In that version a cross of light appears with words about conquering
• •Eusebius says he heard it from the emperor himself, under oath
• •The standard as an object is described in detail only by Eusebius

The episode is among the most examined in Roman history and the caution has specific grounds. The two accounts disagree about the form of the sign, the timing and the nature of the experience. Eusebius wrote long afterwards, was a partisan of the emperor, and did not mention the vision in an earlier work where it would have been relevant. Constantine's coinage continued to carry the sun god for years after the battle, which sits awkwardly with an immediate conversion. And the monogram itself was in use as an abbreviation before this, so its appearance is not necessarily a declaration. The consensus is that something happened and that the accounts of it were shaped considerably afterwards.

The monogram has its own history running alongside the standard and outlasting it by a long way. Formed from the Greek letters chi and rho, the first two of the word for Christ, it was already in use as a scribal abbreviation for the name before any of these events, which is part of why its appearance is hard to read as a declaration. After Constantine it spread rapidly onto coins, military equipment, sarcophagi, mosaics and domestic objects across the empire, and it is one of the commonest finds identifying a late Roman context as Christian. It remains in use on vestments and church furnishings, where it is frequently mistaken for the letters P and X.

Whatever occurred, the consequences were enormous and fairly rapid. Constantine won the battle at the Milvian Bridge outside Rome in October 312 and took the western empire. An agreement the following year ended the persecution of Christians and restored confiscated property across the empire. Imperial patronage followed on a large scale, funding basilicas and endowing churches. The emperor convened and presided over a council at Nicaea in 325 to settle a doctrinal dispute, which set a precedent for imperial involvement in church matters that lasted for centuries. The standard itself remained in use by later emperors, and the monogram became a standard Christian symbol that is still in use.

A Roman standard carrying the first two letters of the Greek word for Christ substituted a new religious content into an existing military form. The two contemporary accounts disagree about whether it followed a dream or a vision, Eusebius wrote decades later and omitted it from an earlier work, and the emperor's coinage kept the sun god for years. The battle was won, persecution ended in 313, and imperial patronage transformed the church.