Roman Emperor Frederick I Barbarossa, leaving Vézelay with his army on 4 July 1190. At first, the French and English crusaders travelled together, but the armies split at Lyon after Richard decided to go by sea from Marseille, whereas Philip took the overland route through the Alps to Genoa. The French and English armies were reunited in Messina, where they wintered together. On 30 March 1191, the French set sail for the Holy Land and on 20 April Philip arrived at Acre, which was already under siege by a lesser contingent of crusaders, and he started to construct siege equipment before Richard arrived on 8 June. By the time Acre surrendered on 12 July, Philip was severely ill with dysentery, which reduced his zeal. Ties with Richard were further strained after the latter acted in a haughty manner after Acre fell to the crusaders. More importantly, the siege of Acre resulted in the death of Philip, Count of Flanders, who held the county of Vermandois proper. His death threatened to derail the Treaty of Gisors that Philip had orchestrated to isolate the powerful Blois-Champagne faction. Philip decided to return to France to settle the issue of succession in Flanders, a decision that displeased Richard, who said, "It is a shame and a disgrace on my lord if he goes away without having finished the business that brought him hither. But still, if he finds himself in bad health, or is afraid lest he should die here, his will be done." On 31 July 1191, the French army of 10,000 men (along with 5,000 silver marks to pay the soldiers) remained in Outremer under the command of Duke Hugh III of Burgundy. Philip and his cousin Peter of Courtenay, Count of Nevers, made their way to Rome, where Philip protested to Pope Celestine III (to no avail) of Richard's abusive manner, and from there returned to France. The decision to return was also fuelled by the realization that with Richard campaigning in the Holy Land, English possessions in northern France would be open to attack. After Richard's delayed return home, the war between England and France would ensue over the possession of English-controlled territories. Conflict with England, Flanders and the Holy Roman Empire Conflict with King Richard the Lionheart, 1191–1199 The immediate cause of Philip's conflict with Richard the Lionheart stemmed from Richard's decision to break his betrothal with Philip's sister