Under the guidance of the Templars they followed the course of the brook Kishon, by the ruins of Endor, to the valley of Jezreel, and traversing the pass through the mountains of Gilboa to Bisan or Scythopolis, they descended into the valley of the Jordan, and pitched their tents on the banks of that sacred river. From Bisan they proceeded up the valley of the Jordan to the lake of Tiberias, skirted its beautiful shores to Bethsaida, passing in front of the strong citadel of Tiberias, and then proceeded across the country to Acre, without meeting an enemy to oppose their progress. The Templars then pressed the christian chieftains to undertake without further loss of time the siege of the important fortress of Mount Thabor, and at the commencement of the autumn the place was regularly invested, but the height and steepness of the mountain rendered the transportation of heavy battering machines and military engines to the summit a tedious and laborious undertaking. The troops suffered from the want of water, their patience was exhausted, and the four kings and their followers, being anxious to return home, speedily found excuses for the abandonment of the siege. The customary scene of disorder and confusion then ensued; a large body of Arab horsemen, which had crossed the Jordan, infested the rear of the retiring crusaders. The disordered pilgrims and foot soldiers were panic-stricken, and fled to the hills; and the retreat would have been disastrous, but for the gallant conduct of the Templars and Hospitallers, who covered the rear and sustained the repeated charges of the Arab cavalry. The two orders sustained immense loss in men and horses, and returned in sorrow and disgust to their quarters at Acre.[102] The Grand Master Philip Duplessies had been unable to take part in the expedition; he was confined to the Temple at Acre by a dangerous illness, of which he died a few days after the return of the Templars from Mount Thabor. Immediately after his decease a general chapter of knights was assembled, and Brother William de Chartres was elevated (A. D. 1217) to the vacant dignity of Grand Master.[103] Shortly after his election he was called upon to take the command of a large fleet fitted out by the order of the Temple against the Egyptians. He set sail from Acre in the month of May, cast anchor in the mouth of the Nile, and proceeded, in conjunction with the crusaders, to lay siege to the wealthy and populous city of Damietta. The Templars pitched their tents in the plain on the left bank of the Nile, opposite the town, and surrounded their position with a ditch and a wall. They covered the river with their galleys, and with floating rafts furnished with military engines, and directed their first attacks against a castle in the midst of the stream, called the castle of Taphnis.