fferentiated historical
development. Their threshold location, by reason of which they first
catch any outward migration from the core of the continent, and their
fertility, which serves as a perennial lure to new comers, whether
peaceful or warlike, combine to give them intense historical activity.
They catch the come and go between their wide hinterland and the
projection of land beyond, the stimulus of new arrivals and fresh blood.
But tragedy too is theirs. The Po Valley has been called "the cockpit of
Europe." Even the little Eider, which marks the base of Jutland, has
been the scene of war between Danes and Germans since the tenth
century.[790] The Indus Valley has again and again felt the shock of
conflict with invading hordes from the central highlands, and witnessed
the establishment of a succession of empires. Peace at the gates of the
Balkan Peninsula has never been of long duration, and the postern door
of Korea has been stormed often enough.

[Sidenote: Peninsular extremities as areas of isolation.]

In contrast to these continental sections which stand in contact with
the solid land-mass behind, the extremities of the peninsulas are areas
of isolation and therefore generally of ethnic unity. They often
represent the last stand of displaced people pressed outward into these
narrow quarters by expanding races in their rear. The vast triangle of
the Deccan, which forms the essentially peninsular part of India, is
occupied, except in the more exposed northwest corner, by the Dravidian
race which once occupied all India, and afterward was pushed southward
by the influx of more energetic peoples.[791] Here they have preserved
their speech and nationality unmixed and live in almost primitive
simplicity.[792] In the peninsular parts of Great Britain, in northern
Scotland. Wales and Cornwall, we find people of Celtic speech brought to
bay on these remote spurs of the land, affiliating little with the
varied folk which occupied the continental side of the island, and
resisting conquest to the last.[793] The mountainous peninsula of western
Connaught in Ireland has been the rocky nucleus of the largest
Celtic-speaking community in the island.[794] Brittany, with a similar
location, became the last refuge of Celtic speech on the mainland of
Europe,[795] the seat of resistance to Norman and later to English
conquest, finally the stronghold of conservatism in the French
Revolution.

[Sidenote: Ethnic unity of peninsu