The house of Gonzaga was already well affected to the Spanish cause, and counted several captains in the imperial army.

Charles showed his favor by raising Mantua to the rank of a Duchy.

It was different with the Republic of Venice and the Duke of Milan.

The Emperor elect had reasons to be strongly prejudiced against them both--against Venice as the most formidable of the French allies in the last war; against Francesco Maria Sforza, as having been implicated, though obscurely, in Morone's conspiracy to drive the Spaniards from Italy and place the crown of Naples on Pescara's head.
Clement took both under his protection.

He had sufficient reasons to believe that the Venetians would purchase peace by the cession of their recent acquisitions on the Adriatic coast, and he knew that the pacification of Italy could not be accomplished without their aid.