held out in expectation of aid from Heraclius.
Heraclius did not intend to disappoint them. He mustered from the vicinity of Antioch and Aleppo an army of some fifty thousand, mostly Armenian and Arab mer- cenaries, and again put it under the command of his brother Theodoras. Realizing the numerical superiority of this army, the Arabian generals immediately abandoned Horns, Damascus and other cities to concentrate about 2500 men on the Yarmuk river east of Lake Tiberias. After a period of skirmishing, the desert tribesmen on August 20, 636, forced a showdown during a dust storm which gave them a decisive advantage. Before the Moslem onslaught the Armenian and Syro-Arab mercenaries could not hold their own. Some were slaughtered then and there; others were driven relentlessly into the river; still others deserted and were caught and annihilated on the other side. Theodorus was one of the victims. The fate of Syria was sealed, as even Heraclius reluctantly admitted.
Damascus and the other cities previously occupied now received the conqueror with open arms. 'We like your rule and justice', declared the natives of Horns, 'far better than the state of tyranny and oppression under which we have been living.' Farther north Aleppo and Antioch were soon reduced. Only the Taurus mountains, natural boundary of Syria, finally halted the uninterrupted advance of Arabian arms. Along the coast Acre, Tyre, Sidon, Beirut, Byblus and Tripoli were taken. Jerusalem held out until 638 and Caesarea, reinforced and supplied by sea, until 640. In seven years (633-640) the entire country was subdued.
This easy conquest of a strategic province of the Byzantine empire is not difficult to explain. The military structure of that empire had been as effectively undermined by the Persian incursions of the early seventh century as the spiritual unity of its society had been disrupted by the Monophysite schism of the middle fifth. Last-minute efforts to effect a
