stward
extension of the German Empire; while their common religions, both
Protestant and Roman Catholic, would help obliterate the old political
fissure. Thus the borderland of a country, so markedly differentiated
from its interior, performs a certain historical function, and becomes,
as it were, an organ of the living, growing race or state.

[Sidenote: Tendency toward defection along political frontiers.]

Location on a frontier involves remoteness from the center of national,
cultural, and political activities; these reach their greatest intensity
in the core of the nation and exercise only an attenuated influence on
the far-away borders, unless excellent means of communication keep up a
circulation of men, commodities, and ideas between center and periphery.
For the frontier, therefore, the centripetal force is weakened; the
centrifugal is strengthened often by the attraction of some neighboring
state or tribe, which has established bonds of marriage, trade, and
friendly intercourse with the outlying community. Moreover, the mere
infusion of foreign blood, customs, and ideas, especially a foreign
religion, which is characteristic of a border zone, invades the national
solidarity. Hence we find that a tendency to political defection
constantly manifests itself along the periphery. A long reach weakens
the arm of authority, especially where serious geographical barriers
intervene; hence border uprisings are usually successful, at least for a
time. When accomplished, they involve that shrinkage of the frontiers
which we have found to be the unmistakable symptom of national decline.

This defection shows itself most promptly in conquered border tribes of
different blood, who lack the bond of ethnic affinity, and whose
remoteness emboldens them to throw off the political yoke. The decay of
the Roman Empire, after its last display of energy under Trajan, was
registered in the revolt of its peripheral districts beyond the
Euphrates, Danube, and Rhine, as also in the rapid Teutonization of
eastern Gaul, which here prepared the way for the assertion of
independence. The border satraps of the ancient Persian Empire were
constantly revolting, as the history of Asia Minor shows. Aragon, Old
Castile, and Portugal were the first kingdoms in the Iberian Peninsula
to throw off Saracen dominion. Mountain ranges and weary stretches of
desert roads enabled the rebellions in Chinese Turkestan and the border
districts of Sungaria in