often the preliminary of great historical movements.  They first expand the geographical horizon, and end in permanent settlements, which involve finally considerable transfers of population, summoned to strengthen the position of the interloper.  Such was the history of the Germanic invasions of Britain, the Scandinavian settlements on the shores of Iceland, Britain, and France, and the incursions of Saharan tribes into the Sudanese states.  Among pastoral nomads war is the rule; the tribe, a mobilized nation, is always on a war footing with its neighbors.  The scant supply of wells and pasturage, inadequate in the dry season, involves rivalry and conflict for their possession as agricultural lands do not.  Failure of water or grass is followed by the decline of the herds, and then by marauding expeditions into the river valleys to supply the temporary want of food.  When population increases beyond the limits of subsistence in the needy steppes, such raids become the rule and end in the conquest of the more favored lands, with resulting amalgamation of race and culture.[154]

[Sidenote:  Primitive war.]

The wars of savage and pastoral peoples affect the whole tribe.  All the able-bodied men are combatants, and all the women and children constitute the spoils of war in case of defeat.  This fact is important, since the purpose of primitive conflicts is to enslave and pillage, rather than to acquire land.  The result is that a whole district may be laid waste, but when the devastators withdraw, it is gradually repopulated by bordering tribes, who make new ethnic combinations.  After the destruction of the Eries by the Iroquois in 1655, Ohio was left practically uninhabited for a hundred and fifty years.  Then the Iroquoian Wyandots extended their settlements into northwestern Ohio from their base in southern Michigan, while the Miami Confederacy along the southern shore of Lake Michigan pushed their borders into the western part.  The Muskingum Valley in the eastern portion was occupied about 1750 by Delawares from eastern Pennsylvania, the Scioto by Shawnees, and the northeast corner of the territory by detachments of Iroquois, chiefly Senecas.[155] The long wars between the Algonquin Indians of the north and the Appalachian tribes of the south kept the district of Kentucky a No Man’s Land, in convenient vacancy for occupation by the white settlers, when they began the westward movement.[156] [Map page 156.]

[Sidenote:  Slavery as form of historical movement.]

This desolation is produced partly by killing, but chiefly by enslavement of prisoners and the flight of the conquered.  Both constitute compulsory migrations of far-reaching effect in the fusion of races and the blending of civilizations.  The thousands of Greek slaves who were brought to ancient Rome contributed to its refinement and polish.  All the nations of the known world, from Briton to Syrian and Jew, were represented in the slave markets of the imperial