Thessalonica (theme) in the context of "Old Church Slavonic"

Old Church Slavonic (OCS) or Old Slavonic (/sləˈvɒnɪk, slæˈvɒn-/ slə-VON-ik, slav-ON-) is the first Slavic literary language and the oldest extant written Slavonic language attested in literary sources. It belongs to the South Slavic subgroup of the Balto-Slavic branch of the Indo-European language family and remains the liturgical language of many Christian Orthodox churches.

Historians credit the 9th-century Byzantine missionaries Saints Cyril and Methodius with standardizing the language and undertaking the task of translating the Gospels and necessary liturgical books into it as part of the Christianization of the Slavs. It is thought to have been based primarily on the dialect of the 9th-century Byzantine Slavs living in the Province of Thessalonica (in present-day Greece).

Nikephoros III Botaneiates (Greek: Νικηφόρος Βοτανειάτης, romanized: Nikēphóros Botaneiatēs; 1002–1081), Latinized as Nicephorus III Botaniates, was Byzantine Emperor from 7 January 1078 to 1 April 1081. He became a general during the reign of Byzantine Emperor Constantine IX Monomachos, serving with distinction during the Pecheneg revolt of 1048–1053. In 1057 he aided Isaac I Komnenos in overthrowing Emperor Michael VI Bringas, leading forces at the decisive Battle of Petroe. Under the Emperor Constantine X Doukas Nikephoros was made doux, first of Thessalonica and subsequently of Antioch. In the latter position he repelled numerous incursions from the Emirate of Aleppo. Constantine X died in 1067 and Empress Eudokia Makrembolitissa married Romanos IV Diogenes; Nikephoros, who had also been a candidate for Eudokia's hand and the position of emperor, was exiled and remained in retirement until Emperor Michael VII summoned him to serve as kouropalates and governor of the Anatolic Theme.

Having insulted Emperor Michael with overly frank appeals for help against the Seljuk Turks in Byzantine Anatolia, Nikephoros decided to protect himself from reprisals by seizing the throne. His military acumen and family renown won him strong support, and he took power in 1078 with the approval of the Byzantine Senate and the citizens of Constantinople. As emperor he faced numerous revolts, including those of Nikephoros Bryennios, Nikephoros Basilakes, and Constantine Doukas, as well as an attempted assassination by the Varangian Guard. Nikephoros performed many acts to increase his legitimacy and support, spending large amounts on donatives for the army and his supporters, forgiving all debt in arrears, and instituting minor legal reforms. Diplomatically, he secured the submission of Theodore Gabras and Philaretos Brachamios, governors of Trebizond and Antioch, respectively, who had become de facto independent of the Byzantine Empire.