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.