The story of the development of Christendom, specifically Byzantium’s portion of it (the Byzantine commonwealth, or oikoumene), is a familiar one; it unfolds across Pontic-Caspian Eurasia. But like all great historical trajectories, it had an inchoate period subject to great debates. These discussions typically hinge on the question: how should we interpret the imperial relationship with the populations of Pontic-Caspian Eurasia throughout their respective ninth- to tenth-century monotheisations? Obolensky supposed the process of establishing the Orthodox commonwealth to have begun in about the sixth century, but was it exclusively Orthodox? And did it actually begin c. 500 as Obolensky supposed, or could it be argued that it began instead with ninth- to tenth-century Byzantine Christianisation? This has major implications for our discussions of both ethnicity and sovereignty in the framework of top-down adoptions of monotheism – in this case, of Byzantine Christianity.

Yet the successful Rus’ Christianisation was possible because of the failure of political détente between Byzantium and Khazaria following the latter’s attempted Judaisation, since tenth- to eleventh-century Byzantine policy was able to expand its ecclesiastical administration in Pontic-Caspian Eurasia only by abandoning the attempts at Christianising Khazaria. Along with the Almušids’ Islamisation, the late-tenth-century Rjurikids’ increasing embrace of Byzantine Orthodox Christianity contributed to Khazaria’s isolation and decline, which is demonstrated in emperor Konstantinos VII Porphyrogennetos’ mid-tenth-century DAI. Because Khazaria’s disappearance was central to the monotheistic foundations of several other dynasties (Rjurikids, Almušids, Piasts, etc.), the topic is the last major debate about Khazaria concerning the larger themes of ethnicity and sovereignty amid the monotheisation of Pontic-Caspian Eurasia.

Khazaria’s Decline and Disappearance

The word ‘decline’ is frequently, if contentiously used by historians. My advisor at the University of Birmingham was not fond of the word. Despite wide disagreement about the word’s usage, it fulfils the vague function of defining certain periods, even if the word choice is seldom explained.