History makes one fact very plain: a people who dwell by the sea, and to whom nature applies some lash to drive them out upon the deep, command opportunity for practically unlimited expansion. In this way small and apparently ill-favored strips of the earth's surface have become the seats of wide maritime supremacy and colonial empire. The scattered but extensive seaboard possession of little Venice and Genoa in the latter centuries of the Middle Ages are paralleled in modern times by the large oversea dominions of the English and Dutch. Seaward expansions of peoples are always of great moment and generally of vast extent, whether they are the coastward movements of inland peoples to get a foothold upon the great oceanic highway of trade and civilization, as has been the case with the Russians notably since the early eighteenth century, and with numerous interior tribes of West Africa since the opening of the slave trade; or whether they represent the more rapid and extensive coastwise and oversea expansions of maritime nations like the English, Dutch, and Portuguese. In either event they give rise to widespread displacements of peoples and a bizarre arrangement of race elements along the coast. When these two contrary movements meet, the shock of battle follows, as the recent history of the Russians and Japanese in Manchuria and Korea illustrates, the wars of Swedes and Russians for the possession of the eastern Baltic littoral, and the numerous minor conflicts that have occurred in Upper Guinea between European commercial powers and the would-be trading tribes of the bordering hinterland. [Sidenote: Ethnic contrast between coast and interior peoples.] A coast region is a peculiar habitat, inasmuch as it is more or less dominated by the sea. It is exposed to inundation by tidal wave and to occupation by immigrant fleets. It may be the base for out-going maritime enterprise or the goal of some oversea movement, the dispenser or the recipient of colonists. The contrast between coast-dwellers and the nearby inland people which exists so widely can be traced not only to a difference of environment, but often to a fundamental difference of race or tribe caused by immigration to accessible shores. The Greeks, crowded in their narrow peninsula of limited fertility, wove an Hellenic border on the skirts of the Black Sea and eastern Mediterranean lands, just as the Carthaginians added a fringe of aliens to North Africa, where the Punic people of the coast presented a marked contrast to the Berbers of the interior. [See map page 251.]