along with the majority of his forces in the great walled park of Mirabello outside the city walls, placing them between Leyva's garrison and the approaching relief army. On 4 February an attack on the park was repelled by the French. Skirmishes and sallies by the garrison continued through the month of February. Medici was seriously wounded and withdrew to Piacenza to recuperate, forcing Francis to recall much of the Milan garrison to offset the departure of the Black Band. On 21 February, imperial troops were repelled by the French when they attempted to storm the gates of the park. Albany's advance towards Naples After the failure of a peace mission proposed by Pope Clement VII, Francis and the pope negotiated an alliance in secret. Negotiations were concluded on 12 December 1524, and a secret treaty was signed by the pope on 5 January. Clement pledged not to assist Charles in exchange for Francis's assistance with the conquest of Naples by giving Albany free passage through his lands. In return, Francis promised to cede lands and maintain Medici rule in Florence. The pope tried to stop Francis from acting immediately, because of the dangers inherent in fighting during the winter months. Against the pope's advice, and the counsel of his own senior commanders, Francis almost immediately detached a portion of his forces under the Duke of Albany, sending 5,000 infantry and 500 cavalry south to aid the pope in the invasion of Naples. The size of the army grew when it was joined by Papal States recruits, and French infantry led by the Italian condottiero (Italian mercenary captain), Renzo da Ceri. Francis's ploy failed to achieve his aim of leading the Spaniards to abandon northern Italy, as the Imperial commanders ultimately decided not to attack Albany but to concentrate on relieving Pavia. Lannoy attempted to intercept the expedition near Fiorenzuola, but suffered heavy casualties and was forced to return to Lodi by the intervention of the Black Bands of Giovanni de' Medici, which had just entered French service. Battle of Pavia On the night of 23 February, Imperial artillery began a bombardment to distract the French, whilst the remainder of the Imperial army moved from their camp to flank the brook that separated the two armies. Ahead of them were sappers, who dismantled part of the park wall as quietly as possible, in an operation that took most of the