At the time, the Bulgarians and the Byzantine Empire were at peace by treaty, and although the Byzantine Emperor was overlord of the Serb lands, he was unable to aid the Serbs in a potential war. Presian I of Bulgaria eventually invaded Serbia, resulting in a three-year-war, in which the Bulgar army was devastated and driven out. Vlastimir then turned to the west, expanding well into the hinterland of Dalmatia. He is the eponymous founder of the Vlastimirović dynasty, the first Serbian dynasty.