Battle of Versinikia in the context of "Army"

The Bulgars (also Bulghars, Bulgari, Bolgars, Bolghars, Bolgari, Proto-Bulgarians) were Turkic semi-nomadic warrior tribes that flourished in the Pontic–Caspian steppe and the Volga region between the 5th and 7th centuries. They became known as nomadic equestrians in the Volga-Ural region, but some researchers trace Bulgar ethnic roots to Central Asia.

During their westward migration across the Eurasian Steppe, the Bulgar tribes absorbed other tribal groups and cultural influences in a process of ethnogenesis, including Iranic, Uralic, and Hunnic tribes. The Bulgars spoke a Turkic language, the Bulgar language of the Oghuric branch. They preserved the military titles, organization, and customs of Eurasian steppes as well as pagan shamanism and belief in the sky deity Tangra.

Michael I Rangabe (also spelled Rhangabe; Greek: Μιχαὴλ Αʹ Ῥαγκαβές, romanized: Mikhaḗl 1 Rhangkabés; c. 770 – 11 January 844) was Byzantine emperor from 811 to 813. A courtier of Emperor Nikephoros I (r. 802–811), he survived the disastrous campaign against the Bulgars and was preferred as imperial successor over Staurakios (r. 811–811), who was severely injured. He was proclaimed emperor by Patriarch Nicephorus I of Constantinople on 2 October 811.

Michael's policies were generally conciliatory, and he was overwhelmingly influenced by the iconodule clerics Nikephoros and Theodore the Stoudite. He improved relations with the Franks, even to the point of recognising Charlemagne as an emperor – although not "of the Romans" – and requesting papal arbitration in the Moechian controversy. His half-hearted leadership of the campaign against the Bulgars resulted in defeat in the Battle of Versinikia. The stratēgos of the Anatolic Theme, Leo the Armenian, a popular and successful general, abandoned Michael on the battlefield but was proclaimed emperor by the military, in what was the last military overthrow of an emperor in Byzantine history. Michael was pressured to abdicate, and he retired to a monastery. His sons were castrated to prevent the continuation of his dynasty.

Leo V the Armenian (Greek: Λέων ὁ Ἀρμένιος, Léōn ho Arménios; c. 775 – 25 December 820) was the Byzantine emperor from 813 to 820. He is chiefly remembered for ending the decade-long war with the Bulgars, as well as initiating the second period of Byzantine iconoclasm.

A senior general of Armenian origin, Leo distinguished himself under Nikephoros I and Michael I Rhangabe, eventually becoming the stratēgos of the Anatolic Theme. Taking advantage of Michael's defeat at the Battle of Versinikia, he forced the emperor to abdicate in his favour. He was able to withhold the blockade of Constantinople by Krum of Bulgaria and, after Krum's death, concluded a 30-year peace with his successor Omurtag.