Upon the death of Abu Bekr, the chief associates of Mohammed around him proclaimed Omar as chalif, and entitled him Chalif, and Prince of the Faithful. In the ten years of his chalifate, from 634 to 644, Omar made the Mohammedan empire. He had exerted great influence over Mohammed himself; he had been most powerful with Abu Bekr, who pointed him out for a successor. The man who had been of violent temper and bloody battles, now sedulously practised the administration of justice. He gave much, and used little for himself. He wore a patched dress, and fed on barley bread and water; he prayed and preached, and ate and slept upon the steps of the mosque among the pilgrims. There he received the messengers of kings. The severe chalif, a sworn foe to all effeminacy, strove to train a rude host to war. Arts he proscribed, even those of house and ship-building. When the great city of Modain, or Ctesiphon, was taken, he commanded the library of the Persian kings to be thrown into the Tigris. When some of his soldiers had put on silken garments which they had looted in Syria, he rubbed their faces in the mud and tore their garments in pieces. Such was the man under whom half-armed nomad tribes broke the armies of Heraclius, and took one after another the cities of Syria. But on the side of the emperor were divided counsels, distrust, rankling enmities; Nestorian and Eutychean heretics hating each other, and still more the sovereign under whom they should have fought as well for a common country as for a common faith. The fate of Syria was decided in a terrible battle on the banks of the Hieromax, or Yarmuk. There, the Saracen generals, Obeidah and Khaled, “The sword of God,” utterly defeated the Greek army of 80,000 men.(63) Obeidah wrote to the chalif Omar: “In the name of the most merciful God, I must make thee to know that I encamped on the Yarmuk, and Manuel was near us with a force such as the Moslem never had a greater. But God struck down that host, and gave us the victory out of His overflowing grace and goodness. God has given to 4030 Moslim the honour of martyrdom. All that fled into the desert and mountains we have put down; have beset all roads and passes; God has made us lords of their lands and riches and children. Written after the victory from Damaskus where I am, and await thy command for the division of the booty. Farewell, and the blessing and grace of God be over thee and all Moslim.” After this, city upon city surrendered in affright. In the winter of 636, Obeidah lay before Jerusalem, from which Heraclius took away the Holy Cross with himself to Constantinople. At Antioch, in his dismay, he asked the question why those miserable half naked barbarians, the Arabs, not to be compared with the Romans in armour, or art of war, beat them in the field. A veteran answered him that the wrath of God was on the Romans, who despised His commands, were guilty of every excess, allowed themselves intolerable oppression and violence.