This treaty was hardly signed, when the ill consequences of his conduct became evident. The Earl of Marche and Arthur immediately renewed their claims and hostilities under the protection of the King of France, who made a strong diversion by invading Normandy. At the commencement of these motions, John, by virtue of a prerogative hitherto undisputed, summoned his English barons to attend him into France; but instead of a compliance with his orders, he was surprised with a solemn demand of their ancient liberties. It is astonishing that the barons should at that time have ventured on a resolution of such dangerous importance, as they had provided no sort of means to support them. But the history of those times furnishes many instances of the like want of design in the most momentous affairs, and shows that it is in vain to look for political causes for the actions of men, who were most commonly directed by a brute caprice, and were for the greater part destitute of any fixed principles of obedience or resistance. The king, sensible of the weakness of his barons, fell upon some of their castles with such timely vigor, and treated those whom he had reduced with so much severity, that the rest immediately and abjectly submitted. He levied a severe tax upon their fiefs; and thinking himself more strengthened by this treasure than the forced service of his barons, he excused the personal attendance of most of them, and, passing into Normandy, he raised an army there. He found that his enemies had united their forces, and invested the castle of Mirebeau, a place of importance, in which his mother, from whom he derived his right to Guienne, was besieged. He flew to the relief of this place with the spirit of a greater character, and the success was answerable. The Breton and Poitevin army was defeated, his mother was freed, and the young Duke of Brittany and his sister were made prisoners. The latter he sent into England, to be confined in the castle of Bristol; the former he carried with him to Rouen. The good fortune of John now seemed to be at its highest point; but it was exalted on a precipice; and this great victory proved the occasion of all the evils which afflicted his life. [Sidenote: A.D. 1203.]