the city. Julius now realized that the Bolognese were openly hostile to the Papacy and would not offer any resistance to the French; left with only a detachment of Venetian cavalry, he resorted to excommunicating d'Amboise, who had in the meantime been convinced by the English ambassador to avoid attacking the person of the Pope and had thus withdrawn to Ferrara. In December 1510, a newly assembled Papal army conquered Concordia and besieged the fortress of Mirandola; d'Amboise, marching to relieve the latter, fell ill and died, briefly leaving the French in disarray; the pope took personal command of the siege, and Mirandola fell in January 1511. Alfonso d'Este, meanwhile, confronted and destroyed the Venetian forces on the Po River, leaving Bologna isolated once more; Julius, afraid of being trapped by the French, departed the city for Ravenna. Cardinal Francesco Alidosi, whom he left behind to command the defense of the city, was no better liked by the Bolognese than Julius himself had been; and when, in May 1511, a French army commanded by Gian Giacomo Trivulzio approached, the citizens of Bologna revolted, expelled Alidosi, and opened their gates to the French. Julius blamed this defeat on the Duke of Urbino, who, finding this quite unfair, proceeded to murder Alidosi in full view of the Papal guard. Holy League In October 1511, Julius proclaimed a Holy League against France. The new alliance included not only Spain and the Holy Roman Empire (which abandoned any pretense of adhering to the League of Cambrai in hopes of seizing Navarre from Queen Catherine and Lombardy from Louis), but also Henry VIII of England who, having decided to use the occasion as an excuse to expand his holdings in northern France, concluded the Treaty of Westminster—a pledge of mutual aid against the French—with Ferdinand on 17 November. Louis now appointed his nephew, Gaston de Foix, to command the French forces in Italy. Foix proved more energetic than d'Amboise and Trivulzio had been; having checked the advance of Ramón de Cardona's Spanish troops on Bologna, he returned to Lombardy to sack Brescia, which had rebelled against the French and garrisoned itself with Venetian troops. Aware that much of the French army would be diverted to deal with the impending English invasion, Foix and Alfonso d'Este besieged Ravenna, the last Papal stronghold in the Romagna, in hopes of forcing the Holy League into a decisive engagement.