Subsequently, during the long dogeship of Francesco Foscari (1423-1457), she devoted herself in good earnest to the acquisition of territory upon the mainland.

Then she entered as a Power of the first magnitude into the system of purely Italian politics.

The Republic of S.Mark owned the sea coast of the Adriatic from Aquileia to the mouths of the Po; and her Lombard dependencies stretched as far as Bergamo westward.

Her Italian neighbors were, therefore, the Duchy of Milan, the little Marquisate of Mantua, and the Duchy of Ferrara.

When Constantinople fell in 1453, Venice was still more tempted to pursue this new policy of Italian aggrandizement.
Meanwhile her growing empire seemed to menace the independence of less wealthy neighbors.