On February 24, 1525 he defeated and took prisoner Francis I by a brilliant attack. D'Ávalos' plan was remarkable for its audacity and for the skill he showed in destroying the superior French heavy cavalry by assailing them in flank with a mixed force of harquebusiers and light horse. It was believed that he was dissatisfied with the treatment he had received from the emperor, and Girolamo Morone, secretary to Francesco II Sforza, duke of Milan, approached him with a scheme for expelling French, Spaniards and Germans alike from Italy, and for gaining a throne for himself. D'Ávalos may have listened to the tempter, but in act he was loyal. He reported the offer to Charles V and put Morone into prison. His health, however, had begun to give way under the strain of wounds and exposure, during late November, and he died at Milan on December 3, 1525.