Moreover, what actually constituted a people ("gens") in the Middle Ages has been rigorously debated. There is no clear evidence that peoples known as Serbs or Croats migrated "en masse" as coherent nations. Rather, some sort of group identity began to form within the Balkans from the late 7th century as Slavic notables formed a system of alliances. This coincides with the final demise of Avar hegemony over the western Balkans. At the same time, the Byzantines had begun to re-establish some control in parts of the Balkans after the 7th-century collapse of imperial control. The establishment of the Byzantine theme of Dyrrhachium facilitated diplomatic contacts between the East Romans and the Adriatic "Sclaviniae". Both Florin Curta and John Fine, among other medievalists, have argued that ethnonyms such as Serb or Croat were primarily political labels referring to a "dux" and his retinue of nobles, while on a lower level it also referred the mass of commoners who inhabited the territory under the (often nominal and transient) rule of such leaders. There is little evidence that a modern notion of nation-type ethnicity, and the values associated with it, existed in medieval societies. Rather, for the general masses, identity was rooted primarily with one's own clan, village and region. As Fine states, "In this large region settled by Slavs, all of whom spoke the same language, certain political entities emerged, and that is all that they were, political entities". Duklja was one such polity, and its subsequent history was closely intertwined with that of Serbia/Rascia and the Byzantine Empire, and as well as Rome and 'western' powers. Duklja is seen as one of the medieval Serb states and was the political and cultural predecessor of modern Montenegro. Little is known about Duklja prior to the 11th century. The main source on the history of early South Slavic states is "De Administrando Imperio" by Emperor Constantine VII (compiled before 952). The work mentions virtually nothing about Duklja apart from that it was settled by Slavs and was ruled by the Byzantine Emperors. It probably did not exist as an established, independent polity before the late 10th century. The Byzantines ruled over coastal cities such as Doclea, Bar, Kotor and the hinterland surrounding these. Archaeological evidence (a personal seal belonging to "Peter of Diokleia") suggests that local officials governed this small region in the name of the Emperor.