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forces. Hence the great role played in the formation of the modern powers by the boundary zones, as we shall see particularly in what follows. The historic civilizations, prior to the Graeco- Roman civilization, have left for us little trustworthy informa- tion on this subject, but quite permit the supposition that the practices were then analogous to those of later epochs. When toward the middle of the Twelfth Dynasty, in about 3000 B. C, Ostirtesen III established his frontier at the rapids of Semneh, he fortified them. He had veritable boundary zones for the less stable parts of the empire, since later acquisitions, such as the boundary zone of Nubia and the eastern boundary zone, Ethiopia, were the most precarious conquest and were maintained solely by military force, which became at a certain moment the center of a new Egyptian empire and the means of a reorganization of Egyp- tian unity; just as in our day Piedmont and previously Branden- burg have been the centers of the formation of Italian unity and German unity, as well as a general military unity. The boundary zones are the true frontiers of attack and defense where the antagonistic efforts of groups which tend to encroach upon each other are manifested. When the boundary zones themselves happen to be transformed into intermediate regions separating two hostile powers, they continue their work as barriers, at the same time acquiring a function already in part peaceful. These are then what are called state buffers, such as at present exist in Asia between England and Russia, and in all the European zone which extends between France and Germany from the North Sea to the Mediterranean. The whole eastern coast of the Mediter- ranean constituted a zone of this kind, serving as a closed field for the empires of the Nile, Tigris, and Euphrates, and favoring in an intermittent fashion peaceful and commercial relations.
The rivers and creeks served to no greater extent as frontiers for the Chaldean empire than for Egypt. They penetrated the center of it. At the east there were mountains limits which are always crossed, and at the west the desert of Arabia, the most powerful obstacle to expansion. The evolution was analogous to that of Egypt. The first Chaldean cities were established along the lower course of the Euphrates or along the navigable streams
