Old Church Slavonic

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

Old Church Slavonic exists because two brothers from Thessalonica were sent on a diplomatic mission and decided the mission needed its own alphabet first. In 863, the Byzantine missionaries Constantine, later known by his monastic name Cyril, and his brother Methodius were invited by Rostislav, the ruler of Great Moravia, to establish a Slavic speaking church hierarchy in his territory, partly as a way to counterbalance the political and religious influence of Bavarian Frankish clergy already active there. Before the brothers traveled, Constantine devised the Glagolitic alphabet, an entirely new set of characters adapted from Greek letterforms with additional signs invented for Slavic sounds Greek had no way to write, and used it to translate the Gospels and core liturgical texts into the Slavic dialect of their native Thessalonica, the language now called Old Church Slavonic. This made Old Church Slavonic the first Slavic language ever committed to writing and the liturgy the brothers built around it the first Christian service conducted in a Slavic vernacular rather than in Greek or Latin. Constantine died in Rome in February 869, only six years into the mission, but Methodius continued the work for another sixteen years, and Old Church Slavonic went on to become the base literary language for Slavic Orthodox Christianity across Eastern Europe, later written in the Cyrillic script credited to the brothers' own students rather than Glagolitic itself, which fell out of everyday use but survived in a handful of Croatian churches for centuries afterward.

This article records tradition as it has been passed down and reported. Its sources are not yet part of the atlas's verified catalogue.

Not everyone welcomed a Christian liturgy conducted in Slavic. When Cyril and Methodius traveled to Venice in 867, on their way to Rome to resolve a jurisdictional dispute with the Latin rite clergy already working in Great Moravia, they were confronted by Frankish churchmen who argued that only three languages, Hebrew, Greek and Latin, the languages named on the inscription over the cross at the crucifixion, could properly be used to worship God. Constantine, who had not yet taken his monastic name of Cyril, answered the challenge directly, citing scripture, including Paul's first letter to the Corinthians on speaking so that a congregation can understand, to argue that no language was intrinsically unfit for praising God. Later writers gave the Frankish position a name, the trilingual heresy, sometimes called the Pilate heresy after the multilingual sign Pilate ordered placed on the cross. The dispute might have ended the brothers' work entirely, but Pope Hadrian II sided with them once they reached Rome, formally approving the Slavic liturgy and reportedly taking part in a service conducted in it himself, a significant endorsement from the one authority the Frankish clergy could not simply override. That papal support did not end the hostility on the ground. After Methodius died in 885, his Frankish rivals moved quickly against his disciples, and many of the Slavic speaking clergy he had trained were driven out of Great Moravia entirely, carrying the Glagolitic alphabet and the Slavic liturgy with them into Bulgaria, where the tradition took root and eventually gave rise to the Cyrillic script that still bears Cyril's name.