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basin of the Euphrates and the Tigris. In Syria it extended its rule toward the interior beyond the mountains. In Egypt it approached the second cataract. In Europe it conquered, not only Thrace, but Dacia beyond the Danube. Accordingly, the mountains of Bastarnia became in this region the strategic point of its frontier against the barbarous Sarmatians. As in the case of the Danube, the empire again crossed the Rhine on the east, and it also made the agri decumates a defense in that quarter.
After Trajan the empire consolidates and completes its Asiatic possessions. In Europe it prolongs the holdings on the Euxine as far as the mouth of the Hypanis and the Borysthenes. The Euxine is thus, like the Mediterranean, transformed into an interior lake and route of communication. On the northwest the frontier is carried as far as the Elbe. From the center to the extremities the great routes, whether military or commercial, run together and complete each other in ramifications that carry out a common internal system of circulation for goods, for men, and for ideas. During all the imperial period the system of routes of communication was completed, not merely in Italy, but through- out the different regions to the remotest extremities. The analogy of their development with that of our railroads is remark- able. Strategic necessities exerted upon their direction an influ- ence at first superior to that of economic needs. Of course, it was necessary in building them to take account of topography and of the situation of the large towns, but these were neglected fre- quently to such an extent that many very important ancient centers found themselves left outside of the great circulating sys- tem ; and it is perhaps more exact to say that the position of the towns was henceforth determined by the routes of communica- tion, than that the latter were located by the position of the towns.
And still, as always, the armed force is pursued by the over- flowing civilization toward the extremities. There were thirty legions under Vespasian in place of twenty-eight in the year 95 A. D., and of twenty-five earlier; but now Dalmatia is stripped of troops. Anterior Spain has only two legions, Africa only one.
