The boundaries of each historical period are established by convention and are usually directly related to events that changed the course of history. Such an event occurred in the year 324, when Constantine the Great became sole emperor of the Roman Empire and decided to move the state capital to Constantinople. Thus, the year 324 marks the beginning of Byzantine history.

The term 'Byzantine' results from Constantine the Great's decision to transform the ancient Greek colony of Byzantis into the capital of the new Empire and to change its name to Constantinople, Constantine's city. Introduced in the 16th century and established as a scientific term in the 17th, the term 'Byzantine' refers to approximately eleven centuries of history.

The figures of Constantine the Great and Justinian dominate the period 324-610. While they had assimilated the Roman tradition, these emperors sought to provide the basis for subsequent developments and for the formation of the Byzantine Empire. The early centuries of Byzantine history were characterized, on the one hand, by efforts to secure the borders of the Empire and to reclaim territories that had belonged to the Roman Empire, and, on the other hand, by the establishment of a definitive Orthodox doctrine and by the series of conflicts that resulted from heretical movements within the Empire.