64 THE AMERICAN JOURNAL OF SOCIOLOGY
could not serve as a frontier. A physical frontier consisting of a river or a mountain is not adequately defended except on the con- dition of being extended. The defensive force of these barriers is insufficient, even from the military point of view without reckon- ing that the social forces tend in addition to extend not merely beyond geographical divisions, but also military limits. Caesar conquered Gaul to guarantee Italy and to assure Spain. Augustus was not content with completing the subjection of the tribes of the Alps, with establishing colonies in Narbonne, and with com- municating regularly through them with the left bank of the Rhine, where he stationed his legions. The Rhine is only a physical frontier. To make it a social frontier, it was necessary to prevent access to it. Accordingly, Augustus advanced upon the right bank, where Varus met with decisive disaster. The advance was pushed into regions which no organized Roman social force had penetrated. The zone had not been prepared for conquest as a sphere of influence. Augustus contented himself, consequently, with annexing Norica, Pannonia, Moesia, and the interior of Dalmatia, and with establishing secure continental communications between the eastern and the western parts of the empire.
Within these limits interior peace is assured the fusion of races and varieties of peoples is complete. Hence all the legions are distributed in the northeast of the empire, upon the banks of the Rhine and of the Danube, in Syria, and in Egypt. All the military forces are at the extremities in proportion to the needs. This is the fusion which took place in the interior as well as in Africa from the year 37 of our era. All the legions are concen- trated in Numidia. Nowhere is the empire any more in arms except against the barbarians; that is to say, against those who are outside the zone of the influence of Roman civilization, or in the zone still partially affected by this influence. The emperor, supreme war-lord, and thus the successor of primitive petty kings, governs directly the frontier countries. He is the head, the front (frons, frontier), armed for attack and defense. The frontiers called geographic are not used except as bases. They are worth- less unless they are combined with a powerful human force to
