In 1092, Grand Prince Vukan defeated an army sent by Byzantine Emperor Alexios I Komnenos. Alexios I responded by sending a much larger army, but it was stopped by Serbian envoys wanting to negotiate. Peace was concluded, and Alexios returned to tackle the plundering Cumans. Vukan however, immediately violated the treaty, launching an operation in the Vardar region, conquering the cities of Vranje, Skopje and Tetovo, with much loot. Vukan then sent messengers to Skopje, attempting to justify his actions as a consequence of unjust administration by the Byzantines. Alexios once again accepted peace, this time with the promise of Serbian hostages (a sign of definite peace), he returned to Constantinople and tasked the local leaders to repair the damaged structures on the border. Vukan did not send the hostages as promised, prompting Alexios to send John Komnenos, his nephew and commander of Dyrrhachium, towards Serbia. Vukan bought time by once again promising peace and hostages, only to simultaneously prepare an attack against them. In the night the Byzantine camp was surprise-attacked, with the majority of Byzantine soldiers being killed. Vukan went on to loot Skopje, Gornji- and Donji Polog, then ravaging Vranje and finally returning to Serbia. Alexios sent a last army, entering Lipljan without resistance, Vukan's messengers offered a conclusive peace and the previously promised hostages, and as Alexios had more problems in other places of the Empire, peace was agreed in 1094, and Vukan surrendered twenty hostages.