The Italian physician John of Procida acted on behalf of Peter in Sicily. John had fled to Aragon after Charles' success at the Battle of Tagliacozzo. John travelled to Sicily to stir up the discontents in favour of Peter and thence to Constantinople to procure the support of Michael VIII Palaiologos. Michael refused to aid the Aragonese king without papal approval, and so John voyaged to Rome and there gained the consent of Pope Nicholas III, who feared the ascent of Charles in the Mezzogiorno. John then returned to Barcelona but the Pope died, to be replaced by Pope Martin IV, a Frenchman and a staunch ally of Charles and the Anjou dynasty. This set the stage for the upcoming conflict.