In 1348, taking advantage of the civil war between the Byzantine emperors John V Palaiologos and John VI Kantakouzenos, the Serbian king Stefan Uroš IV Dušan conquered Epirus, with a number of Albanian mercenaries assisting him. The Byzantine authorities in Constantinople soon re-established a measure of control by making the Despotate of Epirus a vassal state, but meanwhile Albanian clans invaded and seized most of the region. The Albanian Losha and Zenevisi clans founded two short-lived principalities, centered in Arta (1358–1416) and Gjirokastër (1386–1411) respectively. Only the city of Ioannina remained under Greek control during this time. Although Albanian clans gained control of most of the region by 1366/7, their continued division into rival clans meant that they could not establish a single central authority.