The situation looked exceedingly serious for Ferdinand II. On the one side he was being pressed hard by the Turks, and on the other he was beset so closely by the Bohemian rebels that even the very city of Vienna was in danger of falling into their hands. His opponent Frederick V. could rely upon the forces of the /Union/ in the campaign, and besides, as the son-in-law of James I. of England and the nephew of Maurice of Orange the successful leader of the Dutch and the sworn ally of the French Huguenots, Frederick had little difficulty in persuading himself that at last Europe was to be freed from the domination of the House of Habsburg. He marched into Bohemia, and was crowned solemnly at Prague in 1619. But if Frederick could count upon support from many quarters so, too, could Ferdinand. Maximilian II. of Bavaria was active on his side, as were indeed the whole forces of the /League/. Saxony, too, which was devoted to Lutheranism and detested the Calvinist tendencies of Frederick, fearing that a victory for him might mean a victory for Calvinism, ranged itself under the banner of the Emperor. The Pope sent generous subsidies, as did also Spain. Finally, during the course of the campaign Ferdinand was fortunate in having the service of two of the ablest generals of their time, Tilly,[4] who commanded the forces of the /League/, and Wallenstein[5] who had charge of the imperial troops. Maximilian of Bavaria marched into Austria at the head of the army of the /League/ and drove the rebels back into Bohemia, whither he followed them, and inflicted upon them a severe defeat in the battle of the White Mountain (1620). Frederick was obliged to save himself by flight after a reign of a few months. The leaders of the rebellion were arrested and put to death. In return for the services he had rendered Maximilian of Bavaria became ruler of the Palatinate, from which Frederick had been deposed. But though Frederick was defeated the struggle was by no means finished. The Count of Mansfeld, acting on behalf of the /Union/, espoused the cause of the Palgrave and was supported by an army led by Christian IV. of Denmark, Frederick's brother-in-law, who marched into Germany to the aid of his friends. James I. of England, though unwilling to despatch an army, helped by grants of money. The war was renewed with great vigour, but the allies had little chance of success against two such experienced generals as Tilly and Wallenstein. Christian IV. suffered a terrible defeat at the Barenberg near Lutter (1626), and three years later he was forced to agree to the Peace of Lubeck (1629), by which he promised to withdraw from Germany and never again to mix himself up in its domestic affairs.