The overthrow of the Western Roman Empire, in the fifth century, was the beginning of a new era in the world's history. For the time it seemed like a retrogression. The civilization of the ancient world had been overthrown, and the new and higher civilization was far in the future. The central figure in the history of Western Europe during this period is the colossal institution of feudalism. The influence of feudalism was both towards, and away from, centralization. The sub-infeudation of the land was constantly tending towards the creation of new and minute powers, but the pryamiding feature of the system led to the growth of the theory that this should be continued one step higher; and that under the true organization of society there would be found a common world-wide superior sovereign, from whom the kings of the various countries would hold, as the vassals-in-chief in each country held from the king. The memory of the supremacy of the empire of Rome strengthened this view, as did also the claims of the Pope.

For a long period the center of the stage in European history is taken up with the contest between the Pope and the Emperor of the so-called Holy Roman Empire, for this position of suprema'cy. The long contest of the Guelfs and Ghibbelines, however, instead of establishing the supremacy of the leader of either faction, shattered the strength of both and resulted in the splitting up of a large portion of Western Europe into a vast number of minute states.

Medieval history, as generally written, is little more than an account of an endless series of military contests between the different European powers. One great advance, however, is to be noticed over the state of international relations in earlier times. Whatever the practice may be, it had at least come to be recognized in theory, and sometimes followed, that nations owed certain obligations one to another, and that there should be some set of principles governing matters of international intercourse. Two great influences were working towards this end during this period - religion and commerce.