Heads of families, on becoming attached to the soil, naturally had other wants and other customs than those which they had delighted in when they were only the chiefs of wandering adventurers. The strength of their followers was not now so important to them as the security of their castles. Fortresses took the place of armed bodies; and at this time, every one who wished to keep what he had, entrenched himself to the best of his ability at his own residence. The banks of rivers, elevated positions, and all inaccessible heights, were occupied by towers and castles, surrounded by ditches, which served as strongholds to the lords of the soil. (Figs. 10 and 11). These places of defence soon became points for attack. Out of danger at home, many of the nobles kept watch like birds of prey on the surrounding country, and were always ready to fall, not only upon their enemies, but also on their neighbours, in the hope either of robbing them when off their guard, or of obtaining a ransom for any unwary traveller who might fall into their hands. Everywhere society was in ambuscade, and waged civil war--individual against individual--without peace or mercy. Such was the reign of feudalism. It is unnecessary to point out how this system of perpetual petty warfare tended to reduce the power of centralisation, and how royalty itself was weakened towards the end of the second dynasty. When the descendants of Hugh Capet wished to restore their power by giving it a larger basis, they were obliged to attack, one after the other, all these strongholds, and practically to re-annex each fief, city, and province held by these petty monarchs, in order to force their owners to recognise the sovereignty of the King. Centuries of war and negotiations became necessary before the kingdom of France could be, as it were, reformed. [Illustration: Fig. 12.--Knights and Men-at-arms, cased in Mail, in the Reign of Louis le Gros, from a Miniature in a Psalter written towards the End of the Twelfth Century.] The corporations and the citizens had great weight in restoring the monarchical power, as well as in forming French nationality; but by far the best influence brought to bear in the Middle Ages was that of Christianity. The doctrine of one origin and of one final destiny being common to all men of all classes constantly acted as a strong inducement for thinking that all should be equally free. Religious equality paved the way for political equality, and as all Christians were brothers before God, the tendency was for them to become, as citizens, equal also in law.