The alliance, however, between Ferdinand and Maximilian was by no means close. Ferdinand by his marriage with Isabella had united the kingdoms of Castile and Arragon; but after Isabella's death he had no claim to the Crown of Castile, which passed to his daughter Juana. Already Juana's husband, the Archduke Philip, had claimed the regency of Castile, and Ferdinand was only saved by Philip's death from the peril of seeing much of his work undone. The claim to Castile had now passed to the young Charles, and Ferdinand was afraid lest Maximilian should at any time revive it in behalf of his grandson. He was unwilling to help in any way to increase Maximilian's power, and rejoiced that in the results of the League of Cambrai little profit fell to Maximilian's share. The Pope gained all that he wished; Ferdinand acquired without a blow the Venetian possessions in the Neapolitan kingdom; the French arms were triumphant in North Italy; but Venice continued to offer a stubborn resistance to Maximilian. In vain Maximilian implored Ferdinand's help. He was unmoved till the successes of the French awakened in his mind serious alarm. The authors of the League of Cambrai began to be afraid of the catastrophe which they had caused. They did not wish to see the French supreme in Italy, but their combination had gone far to ensure the French supremacy. Pope Julius II. felt himself most directly threatened by the growth of the French power. He resolved to break up the League of Cambrai, and so undo his own work. He tried to gain support from the Swiss and from England. He released Venice from her excommunication, and showed himself steadfastly opposed to France. He did his utmost to induce Ferdinand and Maximilian to renounce the League. Ferdinand was cautious, and only gave his secret countenance to the Pope's designs. Maximilian, anxious to make good his claims against Venice, wavered between an alliance with France and a rupture. Louis XII. of France was embarrassed by the hostility of the Pope, whom he tried to terrify into submission. His troops advanced against Bologna, where Julius II. was residing. The Pope fled, but the French forces did not pursue him. Louis was not prepared to treat the Pope as merely a temporal sovereign, and Rome was spared a siege. But Louis was so ill-judging as to attack the Pope on his spiritual side. He raised the old cry of a General Council for the reform of the Church, and drew to his side a few disaffected cardinals, who summoned a Council to assemble at Pisa.