The first effect of this striking change in the nature of landed property and of public office was to substitute for the centralised state of the Carolingians a lax federal system, in which each unit was a group of men attached to the person of a hereditary superior. This nascent feudalism was often brutal, always summary and short-sighted, in its methods of government. The feudal group was engaged in a perpetual struggle for existence with neighbouring groups. Feudal policy was aggressive; for every lord had his war-band, whom he could only hold together by providing them with adventure and rich plunder; nor could any lord regard himself as safe while a neighbour of equal resources remained unconquered. Furthermore, as though the disintegration of society had not gone far enough, every great fief was in constant danger of civil war and partition. As the lord had treated the King, so he in turn was treated by his vassals. He endowed them with lands, he allowed them to found families, he gave them positions of authority; and then they defied him. In the eleventh century the great fief bristled with castles held by chief vassals of the lord; in the small county of Maine alone we hear of thirty-five such strongholds; generally speaking they were centres of rebellion and indiscriminate rapine. Such feudalism was not a system of government; it was a symptom of anarchy. Yet feudalism had not always been a mere tyranny of the military class over the unarmed population. Like the Roman Empire, that of the Franks had forfeited respect and popularity by misgovernment, by feeble government, by insupportable demands on the personal service of the subject. The land-owner was a less exacting master than the Empire; often he could defend his tenants from imperial exactions. During the invasions of the Northmen and Hungarians, he was impelled by his own interest to guard his estates to the best of his ability. Therefore common men looked to their landlord, or looked about them for a landlord, to whom they could commend themselves. The great estate was the ark of refuge from the general flood of social evils. In the eleventh century the situation changed. The Hungarian tide of invasion was rolled back by a Henry the Fowler and an Otto the Great; the Northmen enrolled themselves as members of the European commonwealth. The petty feudal despot was no longer needed. From a protector he had degenerated into a pest of society. The great political problem of the age was to make him innocuous. It was taken in hand, and it was settled, by a variety of means.