When the Roman Empire divided into east and west in 395, the territories of modern Albania became part of the Byzantine Empire. As in the Roman Empire, some Illyrians rose to positions of eminence in the new empire. Three of the emperors who shaped the early history of Byzantium (reigning from 491 to 565) were of Illyrian origin: Anastasius I, Justin I, and--the most celebrated of Byzantine emperors--Justinian I. In the first decades under Byzantine rule (until 461), Illyria suffered the devastation of raids by Visigoths, Huns, and Ostrogoths. Not long after these barbarian invaders swept through the Balkans, the Slavs appeared. Between the 6th and 8th centuries they settled in Illyrian territories and proceeded to assimilate Illyrian tribes in much of what is now Slovenia, Croatia, Bosnia and Herzegovina, and Serbia. The tribes of southern Illyria, however--including modern Albania--averted assimilation and preserved their native tongue. In the course of several centuries, under the impact of Roman, Byzantine, and Slavic cultures, the tribes of southern Illyria underwent a transformation, and a transition occurred from the old Illyrian population to a new Albanian one. As a consequence, from the 8th to the 11th century, the name Illyria gradually gave way to the name, first mentioned in the 2nd century AD by the geographer Ptolemy of Alexandria, of the Albanoi tribe, which inhabited what is now central Albania. From a single tribe the name spread to include the rest of the country as Arbri and, finally, Albania. The genesis of Albanian nationality apparently occurred at this time as the Albanian people became aware that they shared a common territory, name, language, and cultural heritage. (Scholars have not been able to determine the origin of Shqip'ria, the Albanians' own name for their land, which is believed to have supplanted the name Albania during the 16th and 17th centuries. It probably was derived from shqipe, or "eagle," which, modified into shqipria, became "the land of the eagle.") Long before that event, Christianity had become the established religion in Albania, supplanting pagan polytheism and eclipsing for the most part the humanistic world outlook and institutions inherited from the Greek and Roman civilizations. But, though the country was in the fold of Byzantium, Albanian Christians remained under the jurisdiction of the Roman pope until 732. In that year the iconoclast Byzantine emperor Leo III, angered by Albanian archbishops because they had supported Rome in the Iconoclastic Controversy, detached the Albanian church from the Roman pope and placed it under the patriarch of Constantinople. When the Christian church split in 1054 between the East and Rome, southern Albania retained its tie to Constantinople while northern Albania reverted to the jurisdiction of Rome. This split in the Albanian church marked the first significant religious fragmentation of the country.
Medieval culture
In the latter part of the Middle Ages, Albanian urban society reached a high point of development. Foreign commerce flourished to such an extent that leading Albanian merchants had their own agencies in Venice, Ragusa (modern Dubrovnik, Croatia), and Thessalonica (now Thessaloniki, Greece). The prosperity of the cities also stimulated the development of education and the arts. Albanian, however, was not the language used in schools, churches, and official government transactions. Instead, Greek and Latin, which had the powerful support of the state and the church, were the official languages of culture and literature. The new administrative system of the themes, or military provinces created by the Byzantine Empire, contributed to the eventual rise of feudalism in Albania, as peasant soldiers who served military lords became serfs on their landed estates. Among the leading families of the Albanian feudal nobility were the Thopias, Balshas, Shpatas, Muzakas, Aranitis, Dukagjinis, and Kastriotis. The first three of these rose to become rulers of principalities that were practically independent of Byzantium.