Anjou appointed Hugo de Sully as Captain and Vicar-General of Albania, Durrës, Vlorë, Sopot, Butrint and Corfu. In the following months a great Angevin counteroffensive was prepared. A lot of materials and men including Saracen archers and siege engineers were sent to de Sully, who had captured Spinarizza from Byzantine forces making it his headquarters. The first goal of the expedition was the recapture of the city of Berat, which had been under Byzantine control since 1274. However, Charles' preparations were restrained by Pope Nicholas III who had forbidden Charles from attacking the Byzantine Empire. However, Pope Nicholas III died on August 1280 and for more than six months the Pope's seat was vacant. This gave Charles an opportunity to move on. During Autumn 1280 he gave the order to Hugo de Sully to move on. In December 1280 Angevin forces captured the surroundings of Berat and besieged its castle. Byzantine counteroffensive The Byzantine Emperor was hoping for the Pope to stop his Latin adversaries. In fact after the death in 1276 of Pope Gregory X, the main supporter of the union of the churches, his successors maintained the same course and this restricted Charles' movements. However, in February 1281 Charles of Anjou achieved a diplomatic victory by imposing a French Pope, as the head of the Catholic Church. The Byzantine Emperor Michael VIII was excommunicated by the new Pope and Charles' expedition against him blessed as a new crusade. The situation was very complicated for Michael VIII; however, he sent help to the besieged garrison. The Byzantine army which also included Turkish mercenaries arrived near Berat in March 1281. They were under orders to avoid pitched battle and to focus on ambushes and raids. They managed to defeat Angevin forces by capturing first their commander Hugo de Sully in an ambush. This spread panic throughout his army, routing them from the battlefield. The Angevin army lost the major part of its forces and only a small part found refuge in the Kaninë castle, which was in Angevin hands. The Byzantine army continued its advance further into the territory. They besieged the Angevin bases of Vlorë, Kaninë, and Durrës but could not capture them. The Albanian nobles in the region of Krujë allied themselves with the Byzantine Emperor and he granted them a charter of privileges for their city and bishopric. Charles' preparations and Sicilian Vespers Treaty of Orvieto The