Though the situation had stabilized temporarily by the time of Constantine, waves of non-Roman peoples, most prominently the Thervings, Greuthungs and Huns, began to cross into the territory, first (in the case of the Thervingi) as refugees with imperial permission to take shelter from their foes the Huns, then later as invaders. Turning on their hosts after decades of servitude and simmering hostility, Thervingi under Fritigern and later Visigoths under Alaric I eventually conquered and laid waste the entire Balkan region before moving westward to invade Italy itself.