John V Palaiologos
Some historians consider that the goal of Emperor Dušan was to establish a new, Serbian-Greek Empire, replacing the Byzantine Empire. Ćirković considered his initial ideology as that of the previous Bulgarian emperors, who had envisioned co-rulership. However, starting in 1347, relations with John VI Kantakouzenos worsened, Dušan allied himself with rival John V Palaiologos.