The Sienese exiles assembled together, and put themselves under the command of a leader in the French pay. They marched towards Siena, and arriving before the gates on the evening of the 26th of July 1552, proclaimed _Liberty!_ The people, though unarmed, rose at the cry. They admitted the exiles, and drove the garrison, which merely consisted of 400 soldiers, from the convent of San Domenico, in which they had fortified themselves, and pursued them to the citadel, which was badly fortified and badly victualled. After a few days Franzesi capitulated, and Siena was lost to the emperor. Mendoza was accused of various faults on this occasion; of weakening the garrison, and of not putting, through avarice, the citadel in a state of defence; and, above all, of delay, when he had been warned by Cosmo, and not being on the spot himself to secure the power of his master in the town. These faults, joined to the hatred in which he was held, caused the emperor not long after (1554) to recall him to Spain. While thus employed in Italy as a statesman and a soldier, his active mind led him also to other pursuits. Many inedited philosophical works of his are to be found in Spanish libraries. He wrote a paraphrase of Aristotle, and a translation into Spanish of the Mechanics of that philosopher; he composed Political Commentaries, and a history of the taking of Tunis. In the library of manuscripts at Florence, Sedano tells us there exists a volume in quarto entitled, "Various Works of D. Diego de Mendoza, ambassador of his majesty to Venice, Turkey, and England." On all occasions he showed himself an enthusiastic lover of learning, and a liberal patron of learned men; as a proof of which the bookseller Paulus Manutius dedicated his edition of Cicero to him. Since the days of Petrarch, no man had been so eager to collect Greek manuscripts. He sent to Greece and Mount Athos to procure them, and even made their acquisition a clause in a political treaty with the Sultan. He thus collected a valuable library, which at his death he bequeathed to Philip II., and it forms a precious portion of the library of the Escurial. It is, however, as a poet that his name is most distinguished in literature. He was a friend of Boscan, and entered into his views for enlarging the sphere of Spanish poetry by the introduction of the Italian style. Though a hitter enemy to the spirit of liberty in Italy, he could yet appreciate and profit by the highly advanced state of poetry and literature in that country, of which this very spirit was the parent. It is mentioned in the record of his employments, that he went ambassador to England and Turkey; but it is uncertain at what time these journies were performed; probably before his return to Spain in 1554.