Robert Guiscard and Gregory VII

The repeated excommunications of Robert by the intransigent Gregory VII, in 1074, 1075 and in 1078, after Robert’s attempt to seize the principality of Benevento, led to a sudden deterioration in the relations between the Normans and the papacy.
During the investiture quarrels, the Pope, in serious conflict with Emperor Henry IV, who himself had been excommunicated, could not manage without Norman support.
Thus in 1080, in Ceprano, Robert Guiscard, whom the Pope had called ‘a small Norman vilissime’ – a small humble Norman - a few years earlier, solemnly swore allegiance to the Papal power, who would soon call for his help against the invading German emperor in Rome. In 1084, the duke was now seen to be the defender of the Church of Rome, entering the city in order to save the Pope and then to take him to Salerno under his protection, and true to form, Robert proceeded to sack and pillage the Eternal City.
The two protagonists died in the same year, in 1085 - Gregory VII in May and Robert three months later.