On the decease of Filippo Maria Visconti in 1447 he joined the Aragonese against Venice and Florence; but, presently changing his flag, fought valiantly against Alphonso of Aragon and forced him to raise the siege of Piombino.
The Correggio family never managed to keep possession of it for long, and in 1346 they sold it to the Visconti (who constructed a citadel, La Rocchetta, in 1356, of which some remains exist on the east bank of the river, while the later ate du Pont may be seen on the west bank), and from them it passed to the Sforza.
During the Greco-Turkish War of 1897 Visconti Venosta labored to maintain the Europe-an concert, joined Great Britain in preserving Greece from the worst consequences of her folly, and lent moral and material aid in establishing an autonomous government in Crete.
In the latter part of the city, on a steep elevation, stands the castle of St Peter, originally founded by Theodoric, on the site, perhaps, of the earliest citadel, mostly rebuilt by Gian Galeazzo Visconti in 1393, and dismantled by the French in 180r.
Shortly afterwards his term of office was brought to a close by the failure of an attempt to secure for Italy a coaling station at Sanmen and a sphere of influence in China; but his policy of active participation in Chinese affairs was continued in a modified form by his successor, the Marquis Visconti Venosta, who, entering the reconstructed Pelloux cabinet in May 1899, retained the portfolio of foreign affairs in the ensuing Saracco administration, and secured the despatch of an Italian expedition, 2000 strong, to aid in repressing the Chinese outbreak and in protecting Italian interests in the Far East (July 1900).
His relations to the Lombard nobles were equally at variance with his professed patriotism; and, while still a housemate of Visconti and Correggi, he kept on issuing invectives against the tyrants who divided Italy.
On the death of Gian Galeazzo Visconti in 1402, his large possessions broke up, His neighbours and his generals seized what was nearest to hand.
When the Visconti dynasty ended by the dukes death in 1447, he pretended to espouse the cause of the Milanese republic, which was then re-established; but he played his cards so subtly as to make himself, by the help of Cosimo de Medici in Florence, duke de facto if not de jure.
The tyrants of Milan were aspiring to royal alliances; Gian Galeazzo Visconti had been married to Isabella of France; Violante Visconti, a few years later, was wedded to the English duke of Clarence.
In 1406 it fell under the sway of Cabrino Fondulo, who received with great festivities both the emperor Sigismund and Pope John XXIII., the latter on his way to the council at Constance; he, however, handed it over to Filippo Maria Visconti in 1419.