The whole empire was now obedient to the will of one man, but the ordeal from which it had recently escaped showed how loosely the elements of it were bound together, and with what facility they could be disintegrated. The system of government in force hitherto was that introduced into Assyria by Tiglath-pileser III., which had proved so eminently successful in the time of Sargon and his descendants; Babylon and Ecbatana had inherited it from Nineveh, and Persepolis had in turn adopted it from Ecbatana and Babylon. It had always been open to objections, of which by no means the least was the great amount of power and independence accorded by it to the provincial governors; but this inconvenience had been little felt when the empire was of moderate dimensions, and when no province permanently annexed to the empire lay at any very great distance from the capital for the time being. But this was no longer the case, now that Persian rule extended over nearly the whole of Asia, from the Indus to the Thracian Bosphorus, and over a portion of Africa also. It must have seemed far from prudent to set governors invested with almost regal powers over countries so distant that a decree despatched from the palace might take several weeks to reach its destination. The heterogeneity of the elements in each province was a guarantee of peace in the eyes of the sovereign, and Darius carefully abstained from any attempt at unification: not only did he allow vassal republics, and tributary kingdoms and nations to subsist side by side, but he took care that each should preserve its own local dynasty, language, writing, customs, religion, and peculiar legislation, besides the right to coin money stamped with the name of its chief or its civic symbol. The Greek cities of the coast maintained their own peculiar constitutions which they had enjoyed under the Mernmadas; Darius merely required that the chief authority among them should rest in the hands of the aristocratic party, or in those of an elective or hereditary tyrant whose personal interest secured his fidelity. The Carians,* Lycians,** Pamphylians, and Cilicians*** continued under the rule of their native princes, subject only to the usual obligations. of the _corvee_, taxation, and military service as in past days; the majority of the barbarous tribes which inhabited the Taurus and the mountainous regions in the centre of Asia Minor were even exempted from all definite taxes, and were merely required to respect the couriers, caravans, and armies which passed through their territory. * Herodotus cites among the commanders of the Persian fleet three Carian dynasts, Histiseus, Pigres, and Damasithymus, besides the famous Artemisia of Halicarnassus.