We see, then, that Egyptian conditions exist in a modified form. There is, however, another condition present which was also present in Egypt, though in Egypt its effect was masked by the supreme importance of the desert. As the Tigris and Euphrates approach the sea and flow over the flat alluvium, they spread out in swamps and marshes which form a very considerable protection on three sides. Extensive swamps form very effective protection for small communities ; land may be traversed on foot, water may be crossed by boats, but swamps are to a very large extent impassable. Thus within the circle of marshes an early civilization was possible, all the more because the rivers themselves and their many interlacing branches afforded considerable protection, and because beyond the rivers and the swamps there was a belt of land only thinly inhabited and in parts merging into utter desert. As in Egypt, too, the sea kept off enemies; thus on the south-east, the sea, so much greater in extent than now that the Tigris and Euphrates flowed to the sea by separate mouths, was an effective protection.
This land is Babylonia. Again, as in Egypt, we see that it is the place with its conditions that is the im portant fact in its history, for though little is certain of Babylonia for the 4000 years after 7000 B.C., it is known that two races were concerned in the raising of the civilization in the form in which we know it, and that the earlier race had learned many of the arts of life ere they came into contact with the later.
The , geographical protections were sufficient in a primitive age to keep off enemies and allow of develop ment ; they had also a tendency to divide Babylonia into smaller parts. Thus it is that, though a high state of civilization existed in Babylonia as early as, or even earlier than, the corresponding stage was reached in Egypt, yet a thousand years passed from the time Egypt was welded into a single, state, before the first Baby lonian Empire arose under Sargon of Accad, about 3800 B.c. Before that time the Babylonians had passed a peaceful agricultural existence in various small independent states. Secure from savage foes behind their defences, they had very slowly through thousands of years evolved higher ways of living. They had learned how to make bricks, they had built houses and towns, they had made canals earlier than had the Egyptians, but they had not existed under one ruler. Even after Sargon's time, for another thousand years the tendency seems to have been to consider the polity as a loose confederacy of states bound together by common interests, rather than a single state under a common government.
As the conditions of living improved, it was only natural that the Babylonians should have entered into relations with their neighbours, and that a civilization originally based on agriculture should gradually have given way to one in which trade had a considerable part.
This had important consequences. As long as the Babylonians remained within their defences and settled petty squabbles among themselves, the tendency was to progress free from interference from without, but expansion beyond these defences brought out the weak nesses of the position, and the history of the lowlands of the Tigris and Euphrates from 2500 B.c. onwards is the history of the endeavours of surrounding peoples to become possessed of the fertile heart land. The swamps were sufficient to keep off savages in a primitive age, when almost any protection is complete, but they were not impassable, especially after their area had been greatly reduced by the labours of the Babylonians. Beyond the swamps were districts habitable and in habited by races who, after being brought into contact with a higher ideal of living, themselves became half civilized, and looked with envious eyes on the fertile lands within their grasp. Race after race held Baby lonia and ruled the Babylonians, but the native dynasties were few and unimportant. On the mountains to the east bordering the Iranian plateau were the Elamites ; on the continuation northward of the same highlands were the Kassites. Each held the land of Babylonia for a longer or shorter period, and such of them as de scended to the lowlands adopted the civilization they found there, became separated from their kin among the hills, and were gradually lost amid the other peoples of the plain.
Later, a power from the steppeland on the north-west came to the front. Probably founded by the Baby lonians during the period of expansion, A.Esur or Assyria on the Middle Tigris for long was tributary to Babylonia. But separated by a considerable stretch of country, partly steppe, partly even desert, the tendency was for Assyria to become independent and dominate the more productive land under the mountains, so that by the time Babylonia began to be controlled by foreign kings, Assyria was already a force to be reckoned with.
As long as Babylonia was the centre of civilization the history of Mesopotamia was, in the main, peaceful. Its inhabitants depended on agriculture and trade, and there was little necessity or inducement to embark on conquest. Even when the dynasties from the north eastern hills ruled Babylonia, its essential peacefulness asserted itself, but when Assyria had the upper hand the condition of things was changed.