The Balkan geography, whose northern borders were formed by the Danube River and surrounded by the Black Sea, Aegean and Adriatic Sea, was at a very strategically important point with its location in the center of the vast Roman Empire. Attacks on this region have always threatened both capitals of the Empire. During the early Byzantine period, the most intense attacks came from the north. The Germanic, Hun, Bulgarian, Avar and Slavic attacks were both severe and had permanent consequences for the Bulgarians and the Slavs. For this reason, the Empire always gave importance to the Danube borders in order to protect the Balkans and tried to keep the fortifications in that region strong. The general administration policy of the empire was directly implemented in the Balkans, but some new regulations were made depending on the course of political events. First of all, with the comprehensive reform movements carried out in the 4th century, new small administrative units were created in the provincial administration. Subsequently, similar arrangements were made in the military administration and the border troops were reorganized. A fixed field army has also been established in the region. The focus of all these changes is to separate military and civilian powers. In the following periods, some minor changes were made to this order. However, it can be said that all these are ineffective in preventing attacks on the Balkans. Maybe that is why new measures were considered. In the middle of the 5th century, some steps were taken towards the reunification of military and civil administration. However, no radical changes were made until the establishment of the Danube Bulgarian State at the end of the 7th century. During this period, Slavic invasions occupied most of the Balkans. Byzantine authority largely disappeared in this region. This study aims to determine the administrative system implemented by the Byzantine Empire in the Balkan geography from the 4th to the 7th century and a general chronology of the changes in this system.