John Palaiologos's envoys, who urged him to desert his Frankish allies. The Byzantine historian, George Pachymeres, asserts that the Epirote–Frankish coalition split after Achaean knights disrespected the beautiful Vlach wife of Michael II's bastard son, John Doukas, because William refused to discipline them. Outraged by William's rude remarks about his illegitimate birth, John Doukas deserted to the Nicaeans and convinced his father to abandon the campaign. John's unexpected attack from the rear caused panic and the Franks' retreat quickly turned into a flight. Historian Kenneth Setton considers this whole episode, not reported by the more contemporary Akropolites, doubtful. Akropolites credits the allies' defeat to Michael II's inability to resist the archers' attack. After his flight from the battlefield, the Epirotes either followed his suit or deserted to the Nicaean. As the Nicaean victory seemed inevitable, William fled towards Kastoria. Akropolites writes that William hid under a haystack, but a soldier recognized him by his large protruding teeth. He was shackled and sent to Nicaea together with Anseau of Toucy, Geoffrey of Briel and other Achaean aristocrats. Michael VIII demanded the entire Achaean principality for William's release. William refused, stating that Achaea was "a land acquired by force of arms, held by right of conquest" by the conquerors' descendants, and that he could not surrender his vassals' territory. During his prolonged but comfortable captivity, Guy I of Athens assumed the regency for him in Achaea. The Nicaeans failed to conquer Thessaly and Epirus after their victory at Pelagonia, but their hold of Thessalonica was secured. As the Latin Empire was in ruins and exhausted, Michael VIII decided to re-conquer Constantinople from the Latins. He concluded an alliance with Genoa to secure naval support for the siege, but his general, Alexios Strategopoulos, seized Constantinople without Genoese assistance, taking advantage of the absence of the Latin garrison on 25 July 1261. Michael VIII was again crowned emperor in the Hagia Sophia and quickly deposed his underage co-emperor, John IV. After the fall of the Latin Empire, new negotiations began between Michael VIII and William about the conditions of William's release. They reached a compromise when William agreed to cede Mistra, Grand Magne and Monemvasia. As they had been built or conquered by William, their transfer did not violate Achaean customary law, but he could not cede frontier castles "without the counsel and consent of his liegemen". To legalize the transfer of the three