Meanwhile the power of Normandy continued to wax greater. Even two centuries after this time it comprised a third part of the wealth and importance of the kingdom, and in the days of our own Fifth Henry no advice more dangerous to France could be given to an English King than to preserve by every means the independence of this Duchy. To the France of the eleventh century, it was a far greater peril still. Sullenly hostile, or actively menacing, it was only by perpetual harassing that Normandy could be kept down at all. At last in 1054 the King roused all the cities of Central Gaul, Burgundian, Gascon, Breton and Auvergnat in one combined onset, and gathered them at Mantes, the natural frontier between Normandy and France. Duke William's strategy and daring were equal to his task. He divided the invaders into two, annihilated one division at Mortemer with very little loss, and watched the other with grim merriment as it vanished from his Duchy, afraid to strike a blow. Four years later France and Anjou came on for another attempt. Again the Duke was ready. He caught their hosts where the river Dive cut the army in twain, and fell suddenly with all his knights and clubmen and a thundershower of arrows on the division that held the lower bank. King Henry had to watch in idleness above, while his rear-guard was being helplessly cut to pieces. By the taking of Le Mans in 1063, William made still further preparation for the greater fight that was to come. Presages of the coming struggle were not long in making their appearance.