The Serbs, who had no permanent or well-defined frontier in the east, where their neighbours were the Bulgars, or in the south, where they were the Greeks and Albanians, were protected on the north by the river Save and on the west by the Adriatic. They were split up into a number of tribes, each of which was headed by a chief called in Serbian [)z]upan and in Greek arch[=o]n. Whenever any one of these managed, either by skill or by good fortune, to extend his power over a few of the neighbouring districts he was termed veliki (=great) [)z]upan. From the beginning of their history, which is roughly put at A.D. 650, until A.D. 1196, the Serbs were under foreign domination. Their suzerains were nominally always the Greek emperors, who had ‘granted’ them the land they had taken, and whenever the emperor happened to be energetic and powerful, as were Basil I (the Macedonian, 867-86), John Tzimisces (969-76), Basil II (976-1025), and Manuel Comnenus (1143-80), the Greek supremacy was very real. At those times again when Bulgaria was very powerful, under Simeon (893-927), Samuel (977-1014), and John Asen II (1218-41), many of the more easterly and southerly Serbs came under Bulgarian rule, though it is instructive to notice that the Serbs themselves do not recognize the West Bulgarian or Macedonian kingdom of Samuel to have been a Bulgarian state. The Bulgars, however, at no time brought all the Serb lands under their sway.