During these years, Peter IV of Aragon had sought an alliance with Philip VI of France to prevent a new war with Castile. In 1370 he negotiated a marriage for his heir; John, Duke of Girona with Jeanne of France, daughter of Philip VI but the project failed when the princess died on her journey to Barcelona in 1371. Moreover, Henry II of Castile became an ally necessary to Charles V of France (who had helped get the Castilian throne), as demonstrated with the triumph of his army against the English at the Battle of La Rochelle (June 1372).