But the main lines of the war can be reconstructed with accuracy. The Saracen horde under Abu Obeida emerged from the desert in the spring of 634 and captured Bostra, the frontier city of Syria to the east, by the aid of treachery from within. The Romans collected an army to drive them off, but in July it was defeated at Aijnadin [Gabatha] in Ituraea. Thoroughly roused by this disaster Heraclius set all the legions of the East marching, and sixty thousand men crossed the Jordan and advanced to recover Bostra. The Arabs met them at the fords of the Hieromax, an Eastern tributary of the Jordan, and a fierce battle raged all day. The Romans drove the enemy back to the very gates of their camp, but a last charge, headed by the fierce warrior Khaled, broke their firm array when a victory seemed almost assured. All the mailed horsemen of Heraclius, his Armenian and Isaurian archers, his solid phalanx of infantry, were insufficient to resist the wild rush of the Arabs. Urged on by the cry of their general, “Paradise is before you, the devil and hell-fire behind,” the fanatical Orientals threw themselves on regiment after regiment and drove it off the field. All Syria east of Jordan was lost in this fatal battle. Damascus, its great stronghold, resisted desperately but fell early in 635. Most of its population were massacred. This disaster drew Heraclius into the field, though he was now over sixty, and was beginning to fail in health. He could do nothing; Emesa and Heliopolis were sacked before his eyes, and after an inglorious campaign he hurried to Jerusalem, took the “True Cross” from its sanctuary, where he had replaced it in triumph five years before, and retired to Constantinople. Hardly had he reached it when the news arrived that his discontented and demoralized troops had proclaimed a rebel emperor, though the enemy was before them. The rebel—his name was Baanes—was put down, but meanwhile Antioch, Chalcis, and all Northern Syria fell into the hands of the Arabs. Worse yet was to follow. In the next year, 637, Jerusalem fell, after a desperate resistance, protracted for more than twelve months. The inhabitants refused to surrender except to the Caliph in person, and the aged Omar came over the desert, proud to take possession of the city which Mahomet had reckoned the holiest site on earth save Mecca alone. The Patriarch Sophronius was commanded to guide the conqueror around the city, and when he saw the rude Arab standing by the altar of the Church of the Holy Sepulchre, cried aloud, “Now is the Abomination of Desolation, which was spoken of by Daniel the prophet, truly in the Holy Place.” The Caliph did not confiscate any of the great Christian sanctuaries, but he took the site of Solomon’s Temple, and erected on it a magnificent Mosque, known ever since as the Mosque of Omar.