In February 882, Charles convoked a diet in Ravenna. The duke, emperor, and pope made peace and Guy and his uncle, Guy of Camerino, vowed to return the papal lands. In a March letter to Charles, John claimed that the vows went unfulfilled. In 883, Guy of Camerino, now duke of Spoleto, was accused of treason at an imperial synod held at Nonantula late in May. He returned to Spoleto and made an alliance with the Saracens. Charles sent Berengar against Guy III. Berengar was initially successful until an epidemic of disease, which ravaged all Italy, affecting the emperor and his entourage as well as Berengar's army, forced him to retreat.