Since the early 8th century, Serbia had a relationship of entirely nominal suzerainty with the Byzantine Empire. Serbian rulers were crowned as princes and led entirely independent states linked very precariously to Constantinople. However, beginning at the middle of the 11th century, Serbia waged a series of successive wars against the Byzantines, the end result of which would be Serbia's territorial enlargement and its eventual advancement into a kingdom. The following year, a renewed Byzantine campaign against the Serbs seemed imminent but Vukan managed to negotiate a peace treaty.