This book takes its cue from the concept of “byzantine Commonwealth” originally formulated by Dimitri Obolensky and Garth Fowden to describe the Byzantine political and cultural system in Late Antiquity and the Middle Ages. The term was first proposed by Obolensky in a relatively narrow sense to describe the unique mode of “Byzantium's relations with the peoples of Eastern Europe” during the Middle Ages. According to Obolensky, the Byzantine Commonwealth was based on a sense of cultural commonality between the empire and a number of neighboring East European countries, whose “ruling and educated classes were led to adopt many features of Byzantine civilization, with the result that they were able to share in, and eventually to contribute to, a common cultural tradition.” In Obolensky's opinion, this cultural commonality ran sufficiently deep “to justify the view that, in some respects, [these countries] formed a single international community.” Although politically independent, the members of the commonwealth shared a common cultural identity which provided them with a sense of unity above and beyond political borders.

Fowden has significantly broadened Obolensky's definition by projecting it back into the period between the late fifth and the seventh centuries, and suggesting that during that time an “empire,” a geopolitical entity that dominated earlier Near Eastern history, evolved into a “commonwealth.” The commonwealth represented a new “politico-cultural entity,” in which groups that were more or less politically independent formed a common identity on the basis of shared cultural and religious values.