Chi Rho

The Chi Rho (☧, English pronunciation ˈkaɪ_ˈroʊ; also known as chrismon) is one of the earliest forms of Christogram, formed by superimposing the first two (capital) letters—chi and rho (ΧΡ)—of the Greek word ΧΡΙΣΤΟΣ (Christos) in such a way that the vertical stroke of the rho intersects the center of the chi. The Chi-Rho symbol was used by the Roman Emperor Constantine I (r. 306–337 AD) as part of a military standard (vexillum). Constantine's standard was known as the Labarum. Early symbols similar to the Chi Rho were the Staurogram () and the IX monogram (). In pre-Christian times, the Chi-Rho symbol was also used to mark a particularly valuable or relevant passage in the margin of a page, abbreviating chrēston (good). Some coins of Ptolemy III Euergetes (r. 246–222 BC) were marked with a Chi-Rho. Although formed of Greek characters, the device (or its separate parts) is frequently found serving as an abbreviation in Latin text, with endings added appropriate to a Latin noun, thus XPo, signifying Christo, "to Christ", the dative form of Christus, or χρ̅icola, signifying Christicola, "Christian", in the Latin lyrics of Sumer is icumen in. toc According to Lactantius, a Latin historian of North African origins saved from poverty by the Emperor Constantine the Great (r. 306–337), who made him tutor to his son Crispus, Constantine had dreamt of being ordered to put a "heavenly divine symbol" (coeleste signum dei) on the shields of his soldiers. The description of the actual symbol chosen by Emperor Constantine the next morning, as reported by Lactantius, is not very clear: it closely resembles a Tau-Rho or a staurogram (), a similar Christian symbol. That very day Constantine's army fought the forces of Maxentius and won the Battle of the Milvian Bridge (312), outside Rome. Eusebius of Caesarea (died in 339) gave two different accounts of the events. In his church history, written shortly after the battle, when Eusebius had not yet had contact with Constantine, he does not mention any dream or vision, but compares the defeat of Maxentius (drowned in the Tiber) to that of the biblical pharaoh and credits Constantine's victory to divine protection.