The weakness of Charlemagne’s successors helped the growth in power of the individual nobles. The feudal system developed without check. Families made themselves great by their fighting strength. Dukes and counts held sway without hindrance in their own dominions. Much as this added to their importance it was a disadvantage to them when there was need for concerted action against an enemy. Once Charlemagne saw the piratical crafts of the Northmen enter one of his harbors and he prophesied that they would bring misfortune to his people when he was no longer living to guard them. His prophecy came true, and when the sea robbers penetrated into the country by way of the big northern rivers and attacked the cities on the Seine and the Loire, sacking the churches and carrying away the riches of the monasteries, there was no concerted action among the nobles, and destruction and loss went on little hindered by the inadequate efforts of this or that feudal lord. Paris itself was pillaged more than once, and the abbeys of Saint Denis and Saint Germain-des-Prés paid unwilling tribute to the boldness of the invaders. Charlemagne’s grandsons were not of the mettle to deal sharply with the Northmen. Charles the Bald preferred diplomacy to fighting. His nephew, Charles the Fat, once more united the great king’s possessions, but he was no warrior and when the terrible foes appeared in the Seine he was not ashamed to buy them off. Again and again they came, each time ravaging more fiercely, each time approaching nearer and nearer to Paris which they now threatened to destroy. It was in 885 that Rollo or Rolf, called the Ganger or Walker, because he was so huge that no horse could carry him, led a persistent band before whom the Parisians abandoned their suburbs and withdrew behind the walls of the Cité. They fortified the bridges leading to the northern and southern banks, and under their protection sustained a siege of a year and a half. Abbo, one of the monks of the monastery of Saint Germain-des-Prés, has told us about it in a narrative poem of some 1,200 lines. It all sounds as if the days of Cæsar had come again. The Northmen used machines for hurling weapons and fireballs into the city, and floated fireboats down the river to destroy the bridges. The Parisians retaliated from the wall and the towers. The leaders were Eudes, count of Paris and of the district around the city, and Gozlin, bishop of Paris, both of whom fought manfully, and also took intelligent care to foster the courage of their people. Not a day passed without fighting, and although success usually rested with the practised Northmen the Parisians did not become discouraged or demoralized. The most dramatic episode of the siege came at a time when the swollen Seine swept away the Petit Pont leading to the southern bank, and cut off from their friends the defenders of the Petit Châtelet on the mainland. The garrison numbered but a dozen men