Francis swore upon the Gospels and upon his knightly word that he would fulfill these conditions, but in his own and contemporary opinion the compulsion exercised upon him absolved him from his oath. No sooner was he back in France than he declared the treaty null and void and proceeded to form alliances with all the Italian powers that had become alarmed by the sudden strengthening of the emperor's position in the peninsula,--the pope, Venice, Florence, and even the Sforza who owed everything to Charles. Upon the resumption of hostilities the league displayed the same want of agreement and energy which characterized every coalition of Italian city-states; and soon the Imperialists were able to possess themselves of much of the country. In 1527 occurred a famous episode--the sack of Rome. It was not displeasing to the emperor that the pope should be punished for giving aid to France, although Charles cannot be held altogether responsible for what befell. His army in Italy, composed largely of Spaniards and Germans, being short of food and money, and without orders, mutinied and marched upon the Eternal City, which was soon at their mercy. About four thousand people perished in the capture. The pillage lasted nine months, and the brigands were halted only by a frightful pestilence which decimated their numbers. Convents were forced, altars stripped, tombs profaned, the library of the Vatican sacked, and works of art torn down as monuments of idolatry. Pope Clement VII (1523-1534), a nephew of the other Medici pope, Leo X, had taken refuge in the impregnable castle of St. Angelo and was now obliged to make peace with the emperor. [Sidenote: Peace of Cambrai, 1529] The sack of Rome aroused bitter feelings throughout Catholic Europe, and Henry VIII of England, at that time still loyal to the pope, ostentatiously sent aid to Francis. But although the emperor made little headway against Francis, the French king, on account of strategic blunders and the disunion of the league, was unable to maintain a sure foothold in Italy. The peace of Cambrai (1529) provided that Francis should abandon Naples, Milan, and the Netherlands, but the cession of Burgundy was no longer insisted upon. Francis proceeded to celebrate his marriage with the emperor's sister. [Sidenote: Habsburg Predominance in Italy] Eight years of warfare had left Charles V and the Habsburg family unquestionable masters of Italy. Naples was under Charles's direct government. For Milan he received the homage of Sforza. The Medici pope, whose family he had restored in Florence, was now his ally. Charles visited Italy for the first time in 1529 to view his territories, and at Bologna (1530) received from the pope's hands the ancient iron crown of Lombard Italy and the imperial crown of Rome. It was the last papal coronation of a ruler of the Holy Roman Empire.