Sclaveni raided and settled the western Balkans in the 6th and 7th century. The Serbs are mentioned in "De Administrando Imperio" as having settled the Balkans during the reign of Byzantine Emperor Heraclius (r. 610–641), however, research does not support that the Serbian tribe was part of this later migration (as held by historiography) rather than migrating with the rest of Early Slavs. Through linguistical studies, it is concluded that the Early South Slavs were made up of a western and eastern branch, of parallel streams, roughly divided in the Timok–Osogovo–Šar line. Parts of northwestern Kosovo were part of the Serbian Principality. In the late 9th century the region was seized by the First Bulgarian Empire, while the region switched hands between the Byzantines and Bulgarians until the Byzantine restoration of 1018–19. In 1040–41 a massive Bulgarian rebellion broke out, which included Kosovo. Another rebellion broke out in 1072, in which Serbian prince Constantine Bodin was crowned Emperor of Bulgaria at Prizren, however, despite some initial success, Bodin was eventually captured in southern Kosovo and the rebellion was suppressed. Vukan I, the new independent Serbian Grand Prince, began raiding Byzantine territories, first in Kosovo, advancing into Macedonia (1091–95). He broke several peace treaties which he personally negotiated with the Byzantine Emperor at Zvečan and Lipljan, until finally submitting in 1106.