Julius, meanwhile, had become increasingly concerned by the growing French presence in Italy; more significantly, alienated from Alfonso d'Este by friction over a licence for a salt monopoly in the Papal States and Alfonso's continued forays against Venetian forces to secure his recently reacquired Polesine, he had formulated plans to seize the Duchy of Ferrara, a French ally, and to add its territory to the Papal States. His own forces being inadequate for the venture, the Pope hired an army of Swiss mercenaries, ordering them to attack the French in Milan; he also invited Venice to ally with him against Louis. The Republic, facing a renewed French onslaught, readily accepted the offer.