About the year 570 Mohammed was born in Arabia, and in 610 he declared to the world that he had been commissioned by the angel Gabriel to preach the unity of god. He appears to have been a very remarkable religious enthusiast, who believed himself in his divine mission, and was eminently successful in his arduous undertaking. Idolatry was quickly abolished among the Arabs, and replaced by the religion of Mohammed. On the death of the prophet his successors as vigorously pursued the course he had entered upon. Ali, the general of Khalif Omar’s army, in A.D. 637, captured Jerusalem and conquered Syria in the name of the one true god and his prophet Mohammed. The Khalif rode from Medina to Jerusalem upon a red camel, and, as he entered the conquered city, issued the following proclamation: “In the name of the most merciful God. From Omar Ebno’l Alchitâb to the inhabitants of Œlia. They shall be protected and secured, both in their lives and their fortunes; and their churches shall neither be pulled down nor made use of by any but themselves.” Sophronius, the chief Christian priest, having invited the conqueror to pray in a Christian church, received a polite refusal, Omar contenting himself with kneeling on the steps outside, so that his followers might not have any excuse for seizing the edifice or otherwise annoying the conquered Christians. The Khalif and his followers then pressed northwards, conquered the Roman Emperor Heraclius, sent a fleet to the Hellespont, defeated the Roman fleet, and laid siege to Constantinople, then called Byzantium. Egypt was next conquered, the remnants of the Serapion destroyed, and the whole of North Africa added to the dominions of the Khalif. Spain was then seized upon, and the entire country, as far north as the Loire, annexed to the growing empire. In 732 Charles Martel succeeded in stopping the Saracen foe at Poictiers and driving him back to Spain, thus relieving the anxiety of the Church, which was now becoming intense. In 846 a Mussulman fleet sailed up the Tiber, menaced Rome, and carried away St. Peter’s altar to Africa, the Christian empire being saved from further trouble only by the Mohammedan power being divided into three Khalifates.