Two brothers from Thessaloniki gave the Slavs their first written language
In 862 or 863 a Moravian duke asked Byzantium for a Slavonic liturgy, and the missionaries Cyril and Methodius delivered astonishingly fast: a brand-new alphabet and translated scriptures. So fast, in fact, that scholars suspect the work had already been under way for a planned mission to Bulgaria. Orthodox churches still sing in its descendant today.
Old Church Slavonic is the earliest Slavic literary language and the oldest one preserved in writing, which makes it vital evidence for reconstructing Proto-Slavic, the shared ancestor of every Slavic tongue. The brothers are thought to have based it on the Slavic dialect spoken around their home city of Thessaloniki. Its speakers simply called it Slavic, a word that survives in the native names for Slovak and Slovene. Because several nations claim it, it has also been labelled Old Bulgarian, Old Macedonian and more, but English-language scholarship settles on Old Church Slavonic.
The mission went to Great Moravia, covering today's eastern Czech Republic and western Slovakia, at the request of Duke Rastislav. There the brothers devised the Glagolitic alphabet and rendered key texts such as the Psalter and the Acts of the Apostles. The language served government and church in Great Moravia from 863 to 885. Then Pope Stephen V banned it in favour of Latin in 885, and King Svatopluk I expelled the Byzantine missionaries the following year.
Exile turned into triumph. The brothers' students carried their alphabet to the First Bulgarian Empire, where Boris I welcomed them and founded literary schools at Preslav and Ohrid. At Preslav a new script, Cyrillic, emerged and replaced Glagolitic as Bulgaria's official alphabet in 893. Even so, about two-thirds of the surviving canon of Old Church Slavonic texts is written in Glagolitic, and an angular form of that script lived on in Croatia.
From Bulgaria the language spread to Serbia, Croatia, Bohemia, Lesser Poland and the principalities of Kievan Rus'. By the mid-11th century it had split into regional varieties, collectively called Church Slavonic. For centuries it played a role in the Slavic East much like Latin in the West, with the advantage of staying much closer to everyday speech. It was even an official language in Wallachia and Moldavia until Romanian displaced it during the 16th to 17th centuries.
Source: Old Church Slavonic
