The truce of God, insisted upon by William himself, had helped to the same end. For every male of twelve years old swore to help the Bishop to keep that truce, and by degrees his parishioners combined to organise the safety of their town, "_ex consensu parochianorum_." They used the resources for which all subscribed, and placed them under the control of a "gardien de la Confrerie," or "_fraternarum rerum custos_." While these associations preserved the peace of the towns, the King was responsible for the peace of France. But the feeling of independence and the strength of union grew steadily among the citizens year by year. The rise of commerce, which has been already noticed in Rouen, also contributed to this. As cities grew in wealth, they became more and more desirous of escaping from feudal rapacity and of regulating their own affairs by magistrates chosen by themselves. In 1066 Le Mans had already done this. Ten years afterwards Cambrai followed the example. Noyon, Beauvais, Laon, Soissons, and many more clamoured for the charter of their liberty. In the absence of so many overlords at the Crusades the towns beneath the shadow of their castles seized the opportunity of strengthening their position. The same spirit of revolt began to work in Rouen as soon as the strong hand of the Conqueror was taken from the helm of government. But Rouen did not win her civic liberty until she had changed her own Norman dukes for the kings of France. The descendants of Duke William, feeble as they were, were still too near the feudal overlord to admit of rapid change. Yet the leaven was working already, and the disputes of the Conqueror's children fostered the unruly elements in the town.