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