At the beginning of the seventh century the administration of the empire, both civil and military, was essentially what had emerged from the reforms of Diocletian and Constantine in the late third and early fourth centuries. By the end of the eighth century quite different forms of administration were in place. Although we have a fairly clear picture of early seventhcentury Byzantine administration, for the late eighth century the picture is less clear; and because the evidence is both sparse and open to diverse interpretations, the nature and pace of administrative change in this period is still a matter of debate. However, in general terms the change can be described as follows: at the beginning of the seventh century the empire was divided into provinces ruled by civil governors who, though appointed by the emperor, were responsible to the relevant praetorian prefect (the provinces being grouped into four prefectures), and the army was organised quite separately; at the end of the eighth century the empire was divided into districts called themes (themata), which were governed by a military commander (strat¯egos) who was responsible for both the civil and military administration of the province, and directly responsible to the emperor. Let us now look at the changes involved in more detail.