Miniature from the Chronicle of Ioannis Skylitzis,
mid-12th mid-13th century
The mid-6th century saw the first appearance on Byzantine territory of hordes of Slav nomads, who followed in the footsteps of the Avars. By the end of the century the Slavs had reached Macedonia; having failed to capture Thessalonike, they went raiding throughout Greek-speaking lands.
Commencing in the mid-7th century, hordes of Slavs settled in Macedonia, Thrace and the Peloponnese forming isolated groups of autonomous alien and foreign-speaking communities, referred to as 'sklaveniai', which initially obstructed the exercise of Byzantine administration.
In the course of the second half of the 7th century, the inhabitants of these 'sklaveniai' revolted against the Byzantine state. In Macedonia the uprisings were countered with Byzantine military operations (aimed chiefly at securing the Constantinople-Thessalonike road network), during which many Slavs were captured, while others were compelled to re-settle in Asia Minor.
The Slavs who stayed behind were gradually assimilated into the Byzantine state and so were absorbed into the more powerful indigenous Greek population.