Albanians are a native Balkan people, although their exact origin is unclear. The national ideology insists on an unequivocal ethnic relationship with the ancient Illyrians. As little is known about the Illyrians and there are no historical records referring to the existence of the Albanian people during the first millennium C . E ., it is difficult to affirm or deny the relationship. Albanians entered postclassical recorded history in the second half of the eleventh century, and only in this age can one speak with any degree of certainty about the Albanian people as they are known today. In his History written in 1079–1080, the Byzantine historian Michael Attaleiates was the first to refer to the Albanoi as having taken part in a revolt against Constantinople in 1043 and to the Arbanitai as subjects of the duke of Dyrrachium. Similarly, the historian John Scylitzes refers (ca. 1081) to the Arbanites as forming part of the troops assembled in Durrës by Nicephorus Basilacius. It can be assumed that the Albanians began expanding from their mountain homeland in the eleventh and twelfth centuries, initially taking possession of the northern and central coastline and by the thirteenth century spreading southward toward what are now southern Albania and western Macedonia. In the middle of the fourteenth century, they migrated farther south into Greece, initially into Epirus, Thessaly (1320), Acarnania, and Aetolia. By the middle of the fifteenth century, which marks the end of this process of colonization, the Albanians had settled in over half of Greece in such great numbers that in many regions they constituted the majority of the population. Despite these extensive settlements, the Albanians, largely a herding and nomadic people, do not seem to have created any substantial urban centers. There were no noticeable Albanian communities in the cities of the Albanian coast during the Middle Ages.