He usurped the throne of the young emperor of Nicaea, John IV, for whom he had been regent. He then recovered Constantinople and returned the Byzantine capital there, and was crowned Byzantine emperor. He attempted to reconcile the two branches of the church at Constantinople and Rome, though a voluntary union between them agreed at the Council of Lyons (1274) was for immediate political purposes and only lasted until 1289. His great rival was Charles I of Anjou and Naples; after the Sicilian Vespers (1282) Angevin power was reduced and Michael’s successor, Andronicus, withdrew from the union with Rome, no longer needing the pope as an ally.