During the 900s CE, disciples of St. Cyril and St. Methodius constructed a new Slavic script in South Slavic regions (Bulgaria, Macedonia) based on capital Greek letters with additions. Confusingly, this later script became known as 'Cyrillic' despite Cyril having created Glagolitic. This new script was simpler than Glagolitic and more closely resembled Greek capital letters, making it easier for Greek-educated clergy to learn. The Cyrillic script spread through Orthodox missionary work throughout Eastern Europe, becoming the standard writing system for Slavic languages in Orthodox regions.

Cyrillic script enabled massive expansion of Slavic Christian literature, including religious poetry, biblical translations, and liturgical texts. This script became foundational for Old Russian literature, Bulgarian medieval poetry, and later Serbian and Ukrainian literary traditions. The script's adoption facilitated translation of Greek Christian poetry into Slavic languages, creating rich traditions of religious verse that influenced later Slavic poets including those of the Russian Orthodox tradition.