in Viterbo, after the cardinals had not reached a decision for months, Charles's troops took control of the town. On 22February 1281 his staunchest supporter, Simon of Brie, was elected pope. Pope Martin IV dismissed his predecessor's relatives and made Charles the senator of Rome again. Guido I da Montefeltro rose up against the Pope, but Charles's troops under Jean d'Eppe stopped the spread of the rebellion at Forlì. Charles also sent an army to Piedmont, but Thomas I, Marquess of Saluzzo, annihilated it at Borgo San Dalmazzo in May. End of the Church union Pope Martin excommunicated Emperor Michael VIII on 10April 1281 because the Emperor had not imposed the Church union in his empire. The Pope soon authorised Charles to invade the empire. Charles's vicar in Albania, Hugh of Sully, had already laid siege to the Byzantine fortress of Berat. A Byzantine army of relief under Michael Tarchaneiotes and John Synadenos arrived in March 1281. Sully was ambushed and captured, his army put to flight and the interior of Albania was lost to the Byzantines. On 3July 1281 Charles and his son-in-law, Philip of Courtenay, the titular Latin emperor, made an alliance with Venice "for the restoration of the Roman Empire". They decided to start a full-scale campaign early the next year. Margaret of Provence called Robert and Otto of Burgundy and other lords who held fiefs in the Kingdom of Arles to a meeting at Troyes in the autumn of 1281. They were willing to unite their troops to prevent Charles's army from taking possession of the kingdom, but Philip III of France strongly opposed his mother's plan and Edward I of England would not promise any assistance to them. Charles acknowledged that his wife held the County of Tonnerre and her other inherited estates as a Burgundian fief, which appeased Robert of Burgundy. Charles's ships started to assemble at Marseilles to sail up the Rhone in the spring of 1282. Another fleet was gathering at Messina to start the crusade against the Byzantine Empire. The empire's collapse Sicilian Vespers Always in need of funds, Charles could not cancel the , although it was the most unpopular tax in the Regno. Instead he granted exemptions to individuals and communities, especially to the French and Provençal colonists, which increased the burden on those who did not enjoy such privileges. The yearly, or occasionally more frequent, obligatory exchange of