But he could not attach the great soldier of fortune to himself.

Sforza took the pay of Florence against his old patron, and in 1441 forced him to a ruinous peace; one of the conditions of which was the marriage of the Duke of Milan's only daughter, Bianca, to the son of the peasant of Cotignola.

Bianca was illegitimate, and Filippo Maria had no male heir.
The great family of the Visconti had dwindled away.

Consequently, after the duke's death in 1447, Sforza found his way open to the Duchy of Milan, which he first secured by force and then claimed in right of his wife.

An adverse claim was set up by the House of Orleans, Louis of Orleans having married Valentina, the legitimate daughter of Gian Galeazzo.[2] But both of these claims were invalid, since the investiture granted by Wenceslaus to the first duke excluded females.