Cosimo de Medici used his network of bank branches across Europe to do more than just make money. They were also used as an intelligence network. Medici cash was spread far and wide to keep him informed about the machinations of Florence’s – and the Medici family’s – enemies. One major enemy during this period was Milan, lead by Duke Filippo Maria Visconti – Immensely fat, fearsomely ugly, rarely appeared in public, loved to roll around naked on the grass and murder his wives – and who made several attempts to invade Florence, urged on by the enemies of the Medici. When Visconti died in 1447, he refused to acknowledge Francesco Sforza as his rightful heir, so Sforza just marched his army into Milan and declared himself the new Duke, which ushered in a new era of peace between Florence and Milan – but caused huge problems in their relationship with Venice, who appealed to the German Holy Roman Emperor Frederick III to intervene in Italy’s affairs.