Unfortunately Charles V., whose presence in Germany might have exercised a restraining influence, was so engrossed in the life and death struggle with France that he had no time to follow the progress of the religious revolt. To complicate the issue still more, Clement VII., who had been friendly to the Emperor for some time after his election, alarmed lest the freedom of the Papal States and of the Holy See might be endangered were the French driven completely from the peninsula, took sides openly against Charles V. and formed an alliance with his opponent. The good fortune that had smiled on the French arms suddenly deserted them. In 1525 Francis I. was defeated at Pavia and taken as prisoner to Spain, where he was forced to accept the terms dictated to him by his victorious rival. On his release in 1526 he refused to abide by the terms of the Treaty, and a new alliance, consisting of the Pope, France, England, Venice, Florence, Milan, and Switzerland was formed against Charles V. Disturbances, fomented by the Italian supporters of the Emperor, broke out in the Papal States, and a German army led by the Prince of Bourbon marched on Rome without the knowledge of Charles, captured the city, plundered its treasures, and for several days wreaked a terrible vengeance on the citizens. Charles, who was in Spain at the time, was deeply grieved when the news was brought to him of the havoc that had been wrought by his subordinates. A temporary peace was concluded immediately between the Emperor and the Pope, and the peace of Barcelona in 1529 put an end to this unholy strife. About the same time the hostilities between Charles and Francis I. were brought to a conclusion by the Peace of Cambrai, and the Emperor, having been crowned by the Pope at Bologna (1530), was free at last to turn his attention to the religious revolution in Germany.[27] During the struggle between Charles V. and the Pope the Lutheran princes had a free hand to do as they pleased, and, indeed, at one time they were not without hope that Charles might be induced to place himself at their head. Besides, owing to the fact that the Turks were advancing on Hungary and were likely to overrun the hereditary dominions of the House of Habsburg, they felt confident that no attempt could be made to suppress Lutheranism by force. At the Diet of Speier, in 1526, John Duke of Saxony, and Philip of Hesse adopted so violent and unconciliatory an attitude that Germany was on the brink of civil war, had not the Archduke Ferdinand, alarmed by the success of the Turks, used all his powers to prevent a division. It was agreed that both sides should unite against the Turks, that a Council should be called within a year to discuss the religious difficulties, and that in the meantime individual rulers were free to enforce or disregard the decree of Worms as they wished.