Babylonia suffered less than Assyria by defeat in battle; its natural resources gave it great recuperative powers, and the native population was ever so intensely patriotic that centuries of alien sway could not obliterate their national aspirations. A conqueror of Babylon had to become a Babylonian. The Amorites and Kassites had in turn to adopt the modes of life and modes of thought of the native population. Like the Egyptians, the Babylonians ever achieved the intellectual conquest of their conquerors. The Assyrian Empire, on the other hand, collapsed like a house of cards when its army of mercenaries suffered a succession of disasters. The kings, as we have indicated, depended on the tribute of subject States to pay their soldiers and maintain the priesthood; they were faced with national bankruptcy when their vassals successfully revolted against them. The history of Assyria as a world power is divided into three periods: (1) the Old Empire; (2) the Middle Empire; (3) the New or Last Empire. We have followed the rise and growth of the Old Empire from the days of Ashur-uballit until the reign of Tukulti-Ninip, when it flourished in great splendour and suddenly went to pieces. Thereafter, until the second period of the Old Empire, Assyria comprised but a few city States which had agricultural resources and were trading centres. Of these the most enterprising was Asshur. When a ruler of Asshur was able, by conserving his revenues, to command sufficient capital with purpose to raise a strong army of mercenaries as a business speculation, he set forth to build up a new empire on the ruins of the old. In its early stages, of course, this process was slow and difficult. It necessitated the adoption of a military career by native Assyrians, who officered the troops, and these troops had to be trained and disciplined by engaging in brigandage, which also brought them rich rewards for their services. Babylonia became powerful by developing the arts of peace; Assyria became powerful by developing the science of warfare. CHAPTER XVI. RACE MOVEMENTS THAT SHATTERED EMPIRES