Affairs of import called him away from his government. On the death of Paul III. his presence was required at Rome to influence the election of a new pope. He left Siena, together with the unfinished citadel and its garrison, under the command of don Juan Franzesi, and repaired to watch the progress of the conclave. Through his intrigues the cardinal del Monte was elected, who took the name of Julian III. The new pope, elected through Spanish influence, adhered to the emperor's interests. He instantly yielded the great point of contention between Paul III. and Charles V., and consented to the restitution of the general council to Trent. Mendoza twice attended this council for the purpose of bringing the cardinals and prelates to a better understanding. On his return the pope named him gonfaloniere of the church; and in this character he subdued Orazio Farnese, who had rebelled. Besides these necessary causes of absence from his government, he was accused of protracting his stay in Rome on account of an amorous intrigue in which he was engaged, and which occasioned a great deal of scandal. The Sienese were on the alert to take advantage of his absence. The rapacity and ill faith displayed by Mendoza effectually weaned them from all attachment to the imperial cause; and when fresh war broke out between Charles and the French king, the Sienese solicited the aid of the latter to deliver them from a tyranny they were unable any longer to endure. The grand duke of Florence had reason to complain of the Spaniards, and especially of Mendoza, who treated him as the vassal of the emperor; yet he was unwilling that the French should gain footing in Tuscany, and besides hoped to advance his own interests, and to add Siena to his dukedom. He discovered a correspondence between that town and the French, and revealed it to Mendoza, offering the aid of an armed force in the emperor's favour. Mendoza, distrusting the motive of his offers, rejected them. He applied to the pope for assistance; but Julian, offended by his conduct on various occasions, evaded the request and remained neutral. Meanwhile, Mendoza, either ignorant of the imminence of the danger, or despising the power of the enemy, took no active measures to prevent the mischief which menaced his government.