expansion to the west by
the strong powers of central Europe, stretched its dominion eastward to
the Pacific and for a short time over to Alaska. The chief expansion of
the German people and the German Empire in historical times has also
been from west to east; but this eastward advance is probably only
retracing the steps taken by many primitive Teutonic tribes as they
drifted Rhineward from an earlier habitat along the Vistula.

[Sidenote: Return movements.]

Since the world is small, it frequently happens that a people after an
interval of generations, armed with a higher civilization, will reenter
a region which it once left when too crude and untutored to develop the
possibilities of the land, but which its better equipment later enables
it to exploit. Thus we find a backward expansion of the Chinese westward
to the foot of the Pamir, and an internal colonization of the empire to
the Ili feeder of Lake Balkash. The expansion of the Japanese into Korea
and Saghalin is undoubtedly such a return current, after an interval
long enough to work a complete transformation in the primitive
Mongolians who found their way to that island home. Sometimes the return
represents the ebbing of the tide, rather than the back water of a
stream in flood. Such was the retreat of the Moors from Spain to the
Berber districts of North Africa, whither they carried echoes of the
brilliant Saracen civilization in the Iberian Peninsula. Such has been
the gradual withdrawal of the Turks from Europe back to their native
Asia, and slow expulsion of the Tartar tribes from Russia to the barren
Asiatic limits of their former territory. [See map page 225.]

[Sidenote: Regions of attraction and repulsion.]

Voluntary historical movements, seeking congenial or choice regions of
the earth, have left its less favored spots undisturbed. Paucity of
resources and isolation have generally insured to a region a peaceful
history; natural wealth has always brought the conqueror. In ancient
Greece the fruitful plains of Thessaly, Boeotia, Elis and Laconia had a
fatal attraction for every migrating horde; Attica's rugged surface,
poor soil, and side-tracked location off the main line of travel
between Hellas and the Peloponnesus saved it from many a rough
visitant,[210] and hence left the Athenians, according to Thucydides, an
indigenous race. The fertility of the Rhine Valley has always attracted
invasion, the barren Black Forest range has repelled and obstr