It was Khalid who fought the decisive battle (634) with the army of Heraclius upon the banks of the Yarmuk, a tributary of the Jordan. The legions, as ever, were without proper cavalry; for seven centuries the ghost of old Crassus had haunted the east in vain; the imperial armies relied upon Christian Arab auxiliaries, and these deserted to the Moslems as the armies joined issue. A great parade of priests, sacred banners, pictures, and holy relics was made by the Byzantine host, and it was further sustained by the chanting of monks. But there was no magic in the relics and little conviction about the chanting. On the Arab side the Emirs and sheiks harangued the troops, and after the ancient Arab fashion the shrill voices of women in the rear encouraged their men. The Moslem ranks were full of believers before whom shone victory or paradise. The battle was never in doubt after the defection of the irregular cavalry. An attempt to retreat dissolved into a rout and became a massacre. The Byzantine army had fought with its back to the river, which was presently choked with its dead.
Thereafter Heraclius slowly relinquished all Syria, which he had so lately won back from the Persians, to his new antagonists. Damascus soon fell, and a year later the Moslems entered Antioch. For a time they had to abandon it again to a last effort from Constantinople, but they re-entered it for good under Khalid.
Meanwhile on the eastern front, after a swift initial success which gave them Hira, the Persian resistance stiffened. The dynastic struggle had ended at last in the coming of a king of kings, and a general of ability had been found in Rustam. He gave battle at Kadessia (637). His army was just such another composite host as Darius had led into Thrace or Alexander defeated at Issus; it was a medley of levies. He had thirty-three war elephants, and he sat on a golden throne upon a raised platform behind the Persian ranks, surveying the battle, which throne will remind the reader of Herodotus, the Hellespont, and Salamis more than a thousand years before. The battle lasted three days; each day the Arabs attacked and the Persian host held its ground until nightfall called a truce. On the third day the Arabs received reinforcements, and towards the evening the Persians attempted to bring the struggle to an end by a charge of elephants. At first the huge beasts carried all before them; then one was wounded painfully and became uncontrollable, rushing up and down between the armies. Its panic affected the others, and for a time both armies remained dumbfounded in the red light of sunset, watching the frantic efforts of these grey, squealing monsters to escape from the tormenting masses of armed men that hemmed them in. It was by the merest chance that at last they broke through the Persian and not through the Arab array, and that it was the Arabs who were able to charge home upon the resulting confusion. The twilight darkened to night, but this time the armies did not separate. All through the night the Arabs smote in the name of Allah, and pressed upon the shattered and retreating Persians. Dawn broke upon the vestiges of Rustam’s army in flight far beyond the litter of the battlefield. Its path was marked by scattered weapons and war material, abandoned transport, and the dead and dying. The platform and the golden throne were broken down, and Rustam lay dead among a heap of dead men....
Already in 634 Abu Bekr had died and given place to Omar, the Prophet’s brother-in-law, as Caliph; and it was under Omar (634-643) that the main conquests of the Moslems occurred. The Byzantine Empire was pushed out of Syria altogether. But at the Taurus Mountains the Moslem thrust was held. Armenia was overrun, all Mesopotamia was conquered and Persia beyond the rivers. Egypt passed almost passively from Greek to Arab; in a few years the Semitic race, in the name of God and His Prophet, had recovered nearly all the dominions it had lost to the Aryan Persians a thousand years before. Jerusalem fell early, making a treaty without standing siege, and so the True Cross which had been carried off by the Persians a dozen years before, and elaborately restored by Heraclius, passed once more out of the rule of Christians. But it was still in Christian hands; the Christians were to be tolerated, paying only a poll tax; and all the churches and all the relics were left in their possession.
Jerusalem made a peculiar condition for its surrender. The city would give itself only to the Caliph Omar in person. Hitherto he had been in Medina organizing armies and controlling the general campaign. He came to Jerusalem (638), and the manner of his coming shows how swiftly the vigour and simplicity of the first Moslem onset was being sapped by success. He came the six-hundred-mile journey with only one attendant; he was mounted on a camel, and a bag of barley, another of dates, a waterskin, and a wooden platter were his provision for the journey. He was met outside the city by his chief captains, robed splendidly in silks and with richly caparisoned horses. At this amazing sight the old man was overcome with rage. He slipped down from his saddle, scrabbled up dirt and stones with his hands, and pelted these fine gentlemen, shouting abuse. What was this insult? What did this finery mean? Where were his warriors? Where were the desert men? He would not let these popinjays escort him. He went on with his attendant, and the smart Emirs rode afar off—well out of range of his stones. He met the Patriarch of Jerusalem, who had apparently taken over the city from its Byzantine rulers, alone. With the Patriarch he got on very well. They went round the Holy Places together, and Omar, now a little appeased, made sly jokes at the expense of his too magnificent followers.
Equally indicative of the tendencies of the time is Omar’s letter ordering one of his governors who had built himself a palace at Kufa, to demolish it again.
“They tell me,” he wrote, “you would imitate the palace of Chosroes,[326] and that you would even use the gates that once were his. Will you also have guards and porters at those gates, as Chosroes had? Will you keep the faithful afar off and deny audience to the poor? Would you depart from the custom of our Prophet, and be as magnificent as those Persian emperors, and descend to hell even as they have done?”[327]