The Slavs took advantage of the desolation left by the nomadic tribes and in the 6th century settled the Balkan Peninsula "(See also: South Slavs)". Aided by the Avars and the Bulgars, the Slavic tribes started in the 6th century a gradual invasion into the lands of Byzantium. They invaded Macedonia and reached as far south as Thessaly and the Peloponnese, settling in isolated regions that were called by the Byzantines "Sclavinias", until they were gradually pacified. Many Slavs came to serve as soldiers in Byzantine armies and settled in other parts of the empire. Many among the Romanised and Hellenised Paeonian, Illyrian and Thracian population of Macedonia were assimilated by the Slavs, but pockets of tribes that fled to the mountains remained independent. A number of scholars today consider that present-day Aromanians (Vlachs), Sarakatsani and Albanians originate from these mountainous populations. The interaction between Romanised and non-Romanised indigenous peoples and the Slavs resulted in linguistic similarities which are reflected in modern Bulgarian, Albanian, Romanian and Macedonian, all of them members of the Balkan language area. The Slavs also occupied the hinterland of Thessaloniki launching consecutive attacks on the city in 584, 586, 609, 620, and 622 AD, however never taking it. The Slavs were often joined in their onslaughts by detachments of Avars, but the Avars did not form any lasting settlements in the region. A branch of the Bulgars led by khan Kuber, however, settled western Macedonia and eastern Albania around 680 AD and also engaged in attacks on Byzantium together with the Slavs. By this time, the whole Macedonia region was inhabited by several different ethnicities, with South Slavs being the overall majority in the northern fringes of Macedonia while Greeks dominated the highlands of western Macedonia, the central plains, and the coastline.