Scarcely ten years after Mahomet's death the fairest lands in the north of Arabia and the northwest of Africa acknowledged the supremacy of the Arabs who, with the sword in one hand and the Koran in the other, swept across the borders of Arabia with the cry: "There is no God but Allah, and Mahomet is his prophet." Although there was no distinguished man at the head of the Arab troops, they conquered the world with far greater speed than the hosts of Alexander of Macedon. The kingdom of Persia, weakened by old age and dissension, succumbed to the first blow, and the Byzantine provinces, Palestine, Syria, and Egypt, whose inhabitants had but little sympathy with the intriguing court of Constantinople, did not offer the slightest resistance to the Arabs. Medina, an oasis in the great desert, a spot unknown to the different nations, became the lawgiver for millions, just as Rome had been in olden times. The various peoples that had been conquered, had no choice but to recognize Mahomet as a prophet and be converted to Islam, or to pay tribute. The Emperor Heraclius had taken Palestine from the Persians only ten years before it was again lost. Jews and Samaritans both helped the Arabs to capture the land, in order that they might be freed from the heavy yoke of the malignant Byzantine rule. A Jew put into the hands of the Mussulmans the strongly-fortified town of Cæsarea, the political capital of the kingdom, which is said to have contained 700,000 fighting men, amongst whom were 20,000 Jews. He showed them a subterranean passage, which led the besiegers into the heart of the town. The Holy City, too, after a short siege, had to yield to the Mahometan arms. The second successor of Mahomet, the Caliph Omar, took personal possession of Jerusalem (about 638), and laid the foundation-stone of a mosque on the site of the Temple. Bishop Sophronius, who had handed over the keys of Jerusalem to Omar, untaught by the change of fate which he had himself experienced, is said to have made arrangements with the Caliph, in capitulating, that the Jews be forbidden to settle in the Holy City. It is true that Jerusalem was looked upon by the Mussulmans as a holy place, and pilgrimages were made thither by them. It was also called the Holy City (Alkuds) by them, but it was to remain inaccessible to its sons. Omar is said to have driven out both Jews and Christians from Tiberias. Thus ceased the literary activity of the school of that place. They, however, received permission to settle there again under the succeeding Caliphs.