When, however, we speak of a Hittite empire we must understand clearly what that means. It was not an empire like that of Rome, where the subject provinces were consolidated together under a central authority, obeying the same laws and the same supreme head. It was not an empire like that of the Persians, or of the Assyrian successors of Tiglath-pileser III., which represented the organised union of numerous states and nations under a single ruler. Such a conception of empire was due to Tiglath-pileser III., and his successor Sargon; it was a new idea in the world, and had never been realised before. The first Assyrian empire, like the foreign empire of Egypt, was of an altogether different character. It depended on the military enterprise and strength of individual monarchs. As long as the Assyrian or Egyptian king could lead his armies into distant territories, and compel their inhabitants to pay him tribute and homage, his empire extended over them. But hardly had he returned home laden with spoil than we find the subject populations throwing off their allegiance and asserting their independence, while the death of the conqueror brought with it almost invariably the general uprising of the tribes and cities his arms had subdued. Before the days of Tiglath-pileser, in fact, empire in Western Asia meant the power of a prince to force a foreign people to submit to his rule. The conquered provinces had to be subdued again and again; but as long as this could be done, as long as the native struggles for freedom could be crushed by a campaign, so long did the empire exist. It was an empire of this sort that the Hittites established in Asia Minor. How long it lasted we cannot say. But so long as the distant races of the West answered the summons to war of the Hittite princes, it remained a reality. The fact that the tribes of the Troad and Lydia are found fighting under the command of the Hittite kings of Kadesh, proves that they acknowledged the supremacy of their Hittite lords, and followed them to battle like the vassals of some feudal chief. If Hittite armies had not marched to the shores of the Ægean, and Hittite princes been able from time to time to exact homage from the nations of the far west, Egypt would not have had to contend against the populations of Asia Minor in its wars with the Hittites, and the figures of Hittite warriors would not have been sculptured on the rocks of Karabel. There was a time when the Hittite name was feared as far as the western extremity of Asia Minor, and when Hittite satraps had their seat in the future capital of Lydia.