This particular historical movement, which during the two centuries of its greatest activity involved larger numbers than the Tartar invasion of Russia or the Turkish invasion of Europe, for a long period gave to black Africa the only historical importance which it possessed for the rest of the world.[159] [Sidenote: Fusion by deported and military colonies.] In higher stages of political development, war aiming at the subjugation of large territories finds another means to fuse the subject peoples and assimilate them to a common standard of civilization.

The purpose is unification and the obliteration of local differences.

These are also the unconscious ends of evolution by historical movement.

With this object, conquerors the world over have used a system of tribal and racial exchanges.

It was the policy of the Incas of ancient Peru to remove conquered tribes to distant parts of the realm, and supply their places with colonists from other districts who had long been subjected and were more or less assimilated.[160] In 722 B.C.the Assyrian king, Sargon, overran Samaria, carried away the Ten Tribes of Israel beyond the Tigris and scattered them among the cities of Media, where they probably merged with the local population.