Between the years 1100 and 1500 A.D. the state-system of Europe passed through changes amounting in their sum-total to a revolution. But the changes which endured, whether they affected political boundaries or constitutions, came about by slow instalments. At no stage of the development was there any general cataclysm such as had followed the dissolution of the Frankish Empire, and was to follow the advent of Napoleon. New ideas matured slowly in the medieval mind; by the twelfth century the forces making for social stability had grown until they balanced those of disruption; and it was only in the age of the Renaissance that the equilibrium was again destroyed. In the interim the vested interests of property and privilege, of religious and secular authority, presented a firm front to the anarchists and radicals. The Jacquerie in France and Wat Tyler's followers in England, the Albigeois of Languedoc and the Hussites of Bohemia, were overwhelmed by armies of conservatives spontaneously banded together in defence of the established order;--while this spirit prevailed among the ruling classes, there was little fear that a revolution of any kind would be effected by a sudden stroke. As in domestic politics, so too in international relations, these solidly established states were habitually inert, strong in defence, but irresolute and sluggish in attack. The age produced no conqueror to sweep through Europe like a whirlwind, because the implements of conquest on the grand scale had either been destroyed or had not yet come into existence. The peoples of Europe had emerged from the nomadic stage of culture, and they were not yet organised as so many armed camps. The feudal host was hard to mobilise, harder still to keep in the field, and at the best an unmanageable weapon; a standing army of mercenary soldiers would have called for taxation heavier and more regular than any ruler dared to demand, or any people could afford to pay. The wars of the Middle Ages have therefore, with few exceptions, a stamp of futility and pettiness. Ambitious enterprises were foredoomed to failure, and powers apparently annihilated by an invading host recovered strength as soon as it had rolled away. In short, on the European and on the national stage alike, medieval politics meant the eternal recurrence of the same problems and disputes, the eternal repetition of the same palliatives and the same plan of campaign. It is true that political science made more progress than the art of war. But substantial reforms of institutions were effected only in a few exceptional communities--in Sicily under the Normans and Frederic II, in England under Henry II and Edward I, in France under Philip Augustus and his successors. Even in these cases the progress usually consists in elaborating some primitive expedient, in developing some accepted principal to the logical conclusion. The more audacious innovators, a Montfort, an Artevelde, a Frederic II, were