conduct peace negotiations with William early in 1259, but he became embroiled in a new conflict between Epirus and Nicaea before the negotiations began. The Nicaean emperor, Theodore II Laskaris, was succeeded by an underage son, John IV Lascaris, in August 1258. An ambitious Nicaean aristocrat overthrew the child emperor's guardians and had himself crowned co-emperor as Michael VIII Palaiologos. The ruler of Epirus, Michael II Komnenos Doukas, wanted to take advantage of the Nicaean power struggles by fostering a wide anti-Nicaean coalition. He offered the hands of his daughters Helena and Anna to the Hohenstaufen ruler of Sicily, Manfred, and William respectively. He promised a generous dowry to William—80,000 , the castle of Liconia and nearby lands in southern Thessaly. Since their possession could strengthen his hold on Oreus, William quickly accepted the offer. He married Anna in Patras late in the summer of 1258. Before the end of the year, he and his father-in-law met in Patras and concluded a formal alliance. According to the Chronicle of the Morea, Michael acknowledged William's claim to a revived Kingdom of Thessalonica. Michael VIII dispatched his brother, John Palaiologos, with fresh troops to Thessalonica. He sent envoys to Epirus, Sicily and Achaea to start peace negotiations, but Michael II, Manfred and William refused. Enforced by newly hired mercenary troops, John Palaiologos launched a full-scale invasion of Epirus. Unable to resist alone, Michael II called for his allies' assistance in the spring of 1259. William assembled the bulk of the Achaean army. The Aragonese version of the Chronicle of the Morea, in this respect a source of dubious reliability, estimates that "eight thousand first-class men-at-arms and twelve thousand men on foot" gathered for the campaign. William led the Achaean army across the Gulf of Corinth and joined his father-in-law at Arta. They marched to southern Thessaly, where reinforcements from Athens, Salona, Negroponte, Naxos and other Aegean islands joined them. After the Frankish and Epirote commanders decided to fight a pitched battle instead of attacking fortified towns, the allies marched to Macedonia as far as the plain of Pelagonia to meet the enemy force in June 1259. Although the combined number of the Epirote–Frankish soldiery outnumbered the Nicaean troops, their command remained divided. John Palaiologos avoided battle, but his Cuman and Turkish archers continuously harassed the enemy camp. As their constant attacks exhausted the Franks and Epirotes, Michael II entered into negotiations with