Background and Sicilian Vespers
Soon after the Vespers itself, the Sicilians turned to Peter of Aragon to deliver them from French dominion. An Aragonese fleet under Peter himself had landed at Collo, now in eastern Algeria, and to those troops the Sicilians sent envoys. Peter was offered the throne of Sicily and accepted. Pope Martin had meanwhile refused to help the Sicilian communes and the rebels were excommunicated, as was the Byzantine emperor and the Ghibellines of northern Italy.
Charles gathered his forces, abandoning Crusading hopes, in Calabria and made a landing near Messina and began a siege. Five months after the Vespers, on 30 August, Peter landed at Trapani. He quickly marched into Palermo and, on 4 September, received the homage of the Sicilians and confirmed their ancient privileges. Only the vacancy of the Palermitan archdiocese prevented a coronation. Charles was still besieging Messina when Peter's forces first met him. Charles was forced to vacate the isle by the end of October and was thenceforth restricted to the mainland. The pope then excommunicated the Aragonese king and deprived him of his kingdom (18 November).
Peter pressed his advantage and by February 1283 he had taken most of the Calabrian coastline. Charles, perhaps feeling desperate, sent letters to Peter demanding they resolve the conflict by personal combat. The invader accepted and Charles returned to France to arrange the duel. Both kings chose six knights to settle matters of places and dates. A duel was scheduled for 1 June at Bordeaux. A hundred knights would accompany each side and Edward I of England would adjudge the contest; the English king, heeding the pope, refused to take part.

Aragonese invasion of Italy

Main article: Aragonese Crusade Sicily against Naples and Aragon