500 They make themselves independent, under the leadership of Kolaib, who now tries to unite his people in a single confederacy, but the plan is frustrated by his assassination. The tribes now lead a warlike, disorganised existence, encroaching slowly upon the Kahtanee kingdoms. During this period the tribe of Koreish becomes prominent. Tradition assigns their origin to Ishmael, and they have become the guardians of the sacred Kaaba. This gives them pre-eminence over all other Arabian clans, and at the beginning of the seventh century A.D. the tribe of Koreish and its Mustareb allies is the most powerful confederacy in Arabia, the Kahtanee kingdoms having become more or less vassals of the Persian and Byzantine empires. THE KINGDOM OF NABATÆA The Nabatæans are a famous people of ancient Arabia. Secure knowledge of their history goes back only to 312 B.C., when Antigonus failed to take their fortress of Petra. They are described by Diodorus as a pastoral and trading people, preserving their liberty in the arid country of Arabia Petræa. At the fall of the Seleucids they extend their territory over the fertile country east of the Jordan. They occupy the Hauran. Pompey reduces them to vassalage, and in 105 A.D. Trajan takes Petra and breaks up the Nabatæan nation. MOHAMMED AND HIS SUCCESSORS (570-661 A.D.) _ca._ 570 Birth of =Mohammed=, of a noble Koreish family, at Mecca. 605-610 Years of meditation, during which the principles of Mohammedanism are developed. 610 Year of the “call,” Mohammed begins to make converts. Opposition to his doctrines increases among the Meccans until 622 he flees with a body of followers to Medina. The Hegira. Beginning of the Mohammedan era. 623 The first mosque built. Mohammed becomes a warrior. 624 First battle for the faith with the Meccans at Bedr. Victory of Mohammed. 625 Battle of Ohod, and victory of the Meccans. 627 War of the Fosse. The Koreish make terms with Mohammed. 628 War against the Jews of Khaibar. 629 War against the Greek subjects in Arabia. 630 Mohammed moves against Mecca. He conquers it. War with the Hawazin. Rapid spread of Islam. 632 Death of Mohammed. He leaves the entire peninsula, with the exception of a few tribes, under one sceptre and one creed. His father-in-law, =Abu Bekr=, is chosen caliph, or representative. An army under Khalid sets out against the Byzantine Empire. Abu Bekr reduces a revolt in Nejd and Yemen, and defends Medina. 633 Khalid, on the lower Euphrates, is called to Syria. 634 Khalid captures Bosrah and overruns the Hauran. Death of Abu Bekr. =Omar= succeeds. 635 Capture of Damascus. 636 Emesa, Heliopolis, Chalcis, Berœa, and Edessa added to the Mohammedan empire. Battle of the Hieromax (Yermuk). Heraclius abandons Syria to the Moslems.