Chi-Rho

The Chi-Rho is two Greek letters placed one on top of the other: chi (X) and rho (P), the first two letters of the word Christos. It is one of the oldest Christian symbols, older than the cross as a marker of the faith. For most of the 4th century, it was the sign that meant Christianity.

The bridge

On 28 October 312 CE, Constantine defeated Maxentius at the Battle of the Milvian Bridge outside Rome and became sole ruler of the Western Roman Empire. Something happened before the battle that changed the relationship between Roman power and Christian symbolism permanently. The two surviving accounts do not agree on what it was.

Eusebius of Caesarea, writing his Life of Constantine after the emperor’s death in 337, described a vision seen by the entire army: a cross of light in the sky above the sun, with the words In Hoc Signo Vinces, “In This Sign You Will Conquer.” That night, Christ appeared to Constantine in a dream and told him to use the sign as a military standard.

Lactantius, writing around 313 to 315, closer to the event itself, described only a dream the night before the battle. Constantine was told to mark his soldiers’ shields with “the heavenly sign of God.” Lactantius described the mark as the letter X with its top bent over, which matches the Chi-Rho monogram.

Constantine won the battle. He attributed the victory to the Christian God. The Chi-Rho went onto the labarum, the imperial military standard, and from there onto coins, buildings, sarcophagi, and the walls of churches across the empire.

Before and after Constantine

The letter combination itself was not new. Greek scribes used chi-rho as a marginal notation in manuscripts, an abbreviation of chrēston (useful), to mark important passages. The overlaid letters appear on some Ptolemaic coins as abbreviations of royal names. Constantine did not invent the monogram. He gave it a new context by placing it at the head of an army and declaring it the sign of the God who had granted him victory.

After the Milvian Bridge, the Chi-Rho spread through the Roman world at the speed of imperial authority. Coins minted from around 315 onward bore the monogram. Helmets and shields carried it into battle. Sculptors carved it on sarcophagi, including the sarcophagus of Junius Bassus, the Roman prefect who died in 359 and whose tomb in the Vatican Museums is one of the finest examples of early Christian funerary art. Painters and weavers put it on church walls and textiles.

In Coptic Egypt, the Chi-Rho appeared alongside the ankh on church lintels, the old Egyptian sign of life standing next to the new Christian sign of Christ. The coexistence was not a contradiction. Coptic Christians saw continuity between the pharaonic past and the Christian present, and the ankh’s meaning (life, life beyond death) mapped easily onto the new faith.

The sign that gave way

The Chi-Rho dominated Christian visual culture for roughly a century. Through the 4th century, it was the symbol a viewer expected to see on a Christian building or object. The plain cross, which would eventually become the universal marker of the faith, was surprisingly rare in early Christian art. The instrument of execution was slow to become an object of devotion.

The shift happened in the 5th century. The cross appeared more frequently on churches, reliquaries, and manuscript decoration. By the 6th century, images of the crucifixion itself had begun to appear, and the cross had overtaken the Chi-Rho as the primary Christian emblem. The Chi-Rho did not disappear. It survived in liturgical contexts, in the decoration of altars and vestments, and in the illuminated manuscripts of the early medieval period. The Book of Kells, produced around 800 CE in an Irish monastery, contains a famous full-page Chi-Rho illumination of extraordinary complexity.

The monogram remains in use in Catholic, Orthodox, and Anglican churches. It appears on vestments, altar cloths, and architectural ornament. But its period of dominance was the 4th century, when it was the mark of a new religion backed by the power of the state, and when two overlaid Greek letters on a military standard changed the direction of Western civilization.

Related reading

• Ankh. The Egyptian sign of life that coexisted with the Chi-Rho on Coptic church walls.
• Eye of Providence. Another Christian symbol that accumulated layers of meaning across centuries.

Sources

Bibliography. The same list is held in the article’s frontmatter for the citation tools that read it programmatically.

• Eusebius of Caesarea, Vita Constantini (Life of Constantine, c. 337–339 CE) — the vision before the Milvian Bridge
• Lactantius, De Mortibus Persecutorum (On the Deaths of the Persecutors, c. 313–315 CE) — the dream account
• Roman coins bearing the Chi-Rho, minted from c. 315 CE onward (British Museum, Bibliothèque nationale de France)
• Sarcophagus of Junius Bassus (359 CE, Vatican Museums) — early Christian funerary use
• Robin M. Jensen, Understanding Early Christian Art (2000) — survey of early Christian visual culture