Alarm for Thessalonica

During the 6th, or early 7th century AD, the Early Byzantine civilization in the Balkans was being fiercely and constantly attacked by the aggressive Avar-Slav invaders. These particular events prompted Emperor Justinian I to establish the Archdiocese Justiniana First, beyond the limits of the Danube, within the province of Mediterranean Dacia.

These attacks were, most likely, the reason the kings formed a central optical line for signalling information for the attacks, from the Danube to Thessalonica, which possibly led to the expansion, or the establishment, of local provincial signal lines to outlying towns.