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.