When the Byzantines were not fighting in their eastern territories, they were able to slowly regain imperial control. This was achieved through its theme system, referring to an administrative province on which an army corps was centered, under the control of a "strategos" ("general"). The theme system first appeared in the early 7th century, during the reign of the Emperor Heraclius, and as the Byzantine Empire recovered, it was imposed on all areas that came under Byzantine control. The first Balkan theme created was that in Thrace, in 680 AD. By 695, a second theme, that of "Hellas" (or "Helladikoi"), was established, probably in eastern central Greece. Subduing the Slavs in these themes was simply a matter of accommodating the needs of the Slavic elites and providing them with incentives for their inclusion into the imperial administration.