Contact with the Orient has always been an important factor in the history of Europe. Centers of civilization and of political power have shifted with every decisive change in the relations of East and West. Opposition between Greek and barbarian may be regarded as the motif of Greek history, as it is a persistent refrain in Greek literature. The plunder of Asia made Rome an empire whose capital was on the Bosphorus more centuries than it was on the Tiber. Mediæval civilization rose to its height when the Italian cities wrested from Constantinople the mastery of the Levantine trade; and in the sixteenth century, when the main traveled roads to the Far East shifted to the ocean, direction of European affairs passed from Church and Empire to the rising national states on the Atlantic. The history of America is inseparable from these wider relations. The discovery of the New World was the direct result of European interest in the Far East, an incident in the charting of new highways for the world's commerce. In the thirteenth and fourteenth centuries Europeans first gained reliable knowledge of Far Eastern countries, of the routes by which they might be reached, above all of the hoarded-treasure which lay there awaiting the first comer. Columbus, endeavoring to establish direct connections with these countries for trade and exploitation, found America blocking the way. The discovery of the New World was but the sequel to the discovery of the Old. From the ninth to the eleventh century the people of Western Europe had lived in comparative isolation. With half the heritage of the Roman Empire in infidel hands, the followers of the Cross and of the Crescent faced each other, like hostile armies, across the sea. The temporary expansion of the Frankish Empire ceased with the life of Charlemagne, and under his successors formidable enemies closed it in on every hand. Barbarian Slav and Saxon pressed upon the eastern frontier, while the hated Moslem, from the vantage of Spain and Africa, infested the Mediterranean and threatened the Holy City. Even the Greek Empire, natural ally of Christendom, deserted it, going the way of heresy and schism. Danger from without was accompanied by disorganization within. In the tenth century the political edifice so painfully constructed by Charlemagne was in ruins. The organization of the Roman Empire and the Gregorian ideal of a Catholic Church, now little more than a lingering tradition, was replaced by the feudal system. Seigneurs, lay and ecclesiastic, warring among themselves for the shadow of power, had neither time nor inclination for the ways of peace or the life of the spirit. Learning all but disappeared; the useful arts were little cultivated; cities fell into decay and the roads that bound them together were left in unrepair; the life of the time, barren alike in hovel and castle, was supported by the crude labor of a servile class. To be complete within itself, secure from military attack and economically self-supporting, were the essential needs which determined the structure of the great fiefs. The upper classes rarely went far afield, while the "rural population lived in a sort of chrysalis state, in immobility and isolation within each seigneury." But the feudal régime, well suited to a period of confusion, could not withstand the disintegrating effects of even the small measure of peace and prosperity which it secured. Increase in population and the necessities of life liberated those expansive social forces, in politics and industry, in intellectual life, in religious and emotional experience, which produced the civilization of the later Middle Ages; that wonderful thirteenth century which saw the rise of industry and the towns, the foundation of royal power in alliance with a moneyed class, the revival of intellectual activity which created the universities and the scholastic philosophy, the intensification of the religious spirit manifesting itself in such varied and perfect forms,—in the simple life of a St. Francis or the solemn splendor of a Gothic cathedral. Of this new and expanding life, the most striking external expression was embodied in the Crusades. Strangely compounded of religious enthusiasm and political ambition, of the redeless spirit of the knight-errant and the cool calculation of the commercial bandit, these half-military and half-migratory movements of the twelfth and thirteenth centuries mark the beginning of that return of the West upon the East which is so persistent a factor in all modern history. Christendom, so long isolated, now first broke the barriers that had closed it in, and once more extended its frontier into western Asia: Norman nobles, establishing the Kingdom of Jerusalem and the Latin Empire, enabled the Church to guard the Holy Sepulchre, while Italian cities reaped a rich harvest from the plunder of Constantinople and the Levantine trade.