Bonnivet appeared in Italy. Colonna was no longer supported by Pescara, but he had at his disposition Giovanni de' Medici, the celebrated leader of the Black Italian Bands, and Antonio de Ley va. The imperial leaders abandoned the western part of the duchy to the French and retired on Milan. If Bonnivet had pressed on he would have found the capital unready for defence. But his delay gave time to improvise protection: and when he arrived an assault appeared impracticable. He determined to endeavour to reduce the city by famine.
Besides Milan, Colonna still held Pavia, Lodi, and Cremona, and wisely confined his efforts to the retention of these important posts. Bonnivet divided his forces and sent Bayard to attack Lodi and Cremona. Lodi fell, but Cremona held out, and Bayard had to be recalled. The election of Clement VII on November 19 gave for the moment strength to the imperial side. Money was sent and the Marquis of Mantua brought aid. Bonnivet was forced to abandon the siege of Milan, and retire upon the Ticino. On December 28 Prospero Colonna died, but Charles de Lannoy, the viceroy of Naples, with the Marquis of Pescara, arrived to take his place, bringing with him a small supply of money and troops. Reinforcements came from Germany, and the Imperialists, now supported more effectively by Venice, were able to take the offensive. They drove Bonnivet from Abbiate-Grasso, then from Vigevano to Novara. The reinforcements which he was eagerly expecting from the Grisons at length arrived at Chiavenna, but found neither men nor money to meet them. Giovanni de' Medici hung upon their flanks and drove the Grisons levies back over the mountains. At length Bonnivet was forced to leave Novara and endeavour to effect a junction with a force of 8000 Swiss, whom he met upon the Sesia. But this relief was too late. The moral of the army was destroyed. The remnants could only be saved by retreat. Bonnivet himself was wounded at this juncture, and the task of conducting the wearied and dispirited troops across the mountains fell upon Bayard. Bayard took command of the rear-guard, and, in protecting the movements of his comrades, fell mortally wounded by the ball of an arquebus (April 30, 1524). With him perished the finest flower of the French professional army in that age, the knight who had raised the ideal of a warrior's life to the highest point. But his last task was successfully accomplished. The Swiss effected their retreat by Aosta, the French by Susa and Briançon. The last garrison of the French in Lombardy capitulated.
Adrian's successor, Giulio de' Medici, Clement VII, had been supported in his election by the imperial influence, in spite of Charles' promises to Wolsey. Giulio had long controlled the papal policy under Leo, and it was assumed that he would tread the same path. But Clement had all the defects of his qualities. Supremely subtle and acute, he had not the constancy to follow up what he had once come to regard as a mistake. He relied upon his own ingenuity and duplicity,
