The empire which this comparatively insignificant force was destined to attack and overthrow was the greatest which the world had as yet seen, and had already subsisted for two hundred years. It had been founded by Cyrus the Great, and extended by his successors till it embraced all Asia from the shores of the Aegean and the Levant to the regions of the Jaxartes and the Indus. It was divided by the great belt of desert, which stretches almost continuously from the Persian Gulf to the Sea of Aral, into two great sections which differed widely both in their physical aspect and the character of their inhabitants. The eastern tribes living amid mountains and deserts were rude, but distinguished for their hardihood, their love of independence, and their martial prowess. The western Asiatics, on the other hand, who inhabited those fair and fertile countries which had been the earliest seats of civilisation, were singularly deficient in these qualities. Enervated by ease and the affluence of luxuries, they offered but a feeble resistance to Alexander, and bent their necks submissively to his yoke. He had quite a different experience when he came into conflict with the tribes of the Oxus, Jaxartes, and Indus. They resisted him with the utmost spirit and determination, rose against him even after defeat, and succeeded in inflicting a signal disaster on his arms. The system by which the vast empire was governed may be described as a rigid monarchy. It was divided by Darius Hystaspes into twenty provinces, a number which was afterwards much augmented probably by the subdivision of the larger ones. The government of each was committed to a satrap[8] whose powers were almost despotic. He collected the revenues, from which, besides defraying the expenses of his own administration, he was obliged to remit a fixed amount of annual tribute to the royal treasury. The Indian satrapy, which probably included Baktria and was limited to the regions west of the Indus, paid the largest tribute, which, as we learn from Herodotos, amounted to the immense sum of 360 talents of gold dust.