Rastislav of Moravia in the context of "Glagolitic alphabet"

The Glagolitic script (/ˌɡlæɡəˈlɪtɪk/ GLAG-ə-LIT-ik, ⰳⰾⰰⰳⱁⰾⰻⱌⰰ, glagolitsa) is the oldest known Slavic alphabet. It is generally agreed that it was created in the 9th century for the purpose of translating liturgical texts into Old Church Slavonic by Saint Cyril, a monk from Thessalonica. He and his brother Saint Methodius were sent by the Byzantine Emperor Michael III in 863 to Great Moravia after an invitation from Rastislav of Moravia to spread Christianity there. After the deaths of Cyril and Methodius, their disciples were expelled from Moravia, and they moved to the First Bulgarian Empire instead. The Early Cyrillic alphabet, which was developed gradually in the Preslav Literary School by scribes who incorporated some Glagolitic letters when writing in the Greek alphabet, gradually replaced Glagolitic in that region. Glagolitic remained in use alongside the Latin script in the Kingdom of Croatia and alongside Cyrillic until the 14th century in the Second Bulgarian Empire and the Serbian Empire; in later periods, it was used mainly for cryptographic purposes.

Glagolitic also spread to the Kievan Rus' and the Kingdom of Bohemia. Although its use declined there in the 12th century, some manuscripts in the territory of the former retained Glagolitic inclusions for centuries. It had also spread to Duklja and Zachlumia in the Western Balkans, from where it reached the March of Verona. There, the Investiture Controversy afforded it refuge from the opposition of Latinizing prelates and allowed it to entrench itself in Istria, from which place it spread to nearby lands. It survived there and as far south as Dalmatia without interruption into the 20th century for Church Slavonic in addition to its use as a secular script in parts of its range, which at times extended into Bosnia, Slavonia, and Carniola, in addition to 14th–15th century exclaves in Prague and Kraków, and a 16th-century exclave in Putna.