The Normans had a genius for adaptability and this was demonstrated know where more than in southern Italy who they took of the Byzantines, and in Sicily, which was taken from the Arabs.
Small groups of invaders, essentially adventurers, at first became important as professional soldiers, serving in the incessant conflicts in southern Italy. They then seized power. Richard of Aversa succeeded in becoming Prince of Capua, but the most dynamic was Robert Guiscard, the sixth of the ten sons of Tancred d’Hauteville, a poor Norman noble, all of who sought their fortune in southern Italy. In 1059 Pope Nicholas II recognised his as Duke of Apulia in return for the promise of Norman support against the Holy Roman Emperor. In 1060 Guiscard drove the Byzantines from Calabria; in 1071 he captured Bari and Brindisi, the main centres of Byzantine power in Italy. The Lombard principality of Salerno followed in 1077 and in 1081 Guiscard crossed the Adriatic, captured Corfu and defeated the Byzantine Emperor, Alexius Comnenus, at Durazzo. He died while preparing to attack Constantinople. The youngest of Robert’s brothers, completed the conquest of Sicily: Messina had already fallen in 1061 and Catania in 1071, but the conquest was only completed in 1090. He also captured Malta. The basis of a powerful state had now been created.
Roger II of Sicily gained control of the whole of southern Italy in 1130 creating a kingdom that united his dominions. Where the Normans seized power they replaced the social elite, but there was no mass-displacement of the original population and much of the earlier administrative structure continued.
Between 1190-4 the Kingship was passed to the Holy Roman Emperor Henry VI, who had married the heiress to the kingdom of Sicily. This made the ruling house of Germany, the Hohenstaufens, the wealthiest rulers in Europe. In 1268 the thrown of Sicily was transferred to the Angevins after the defeat of Conradin at Tagliacozzo in 1268. This transfer lasted only until 1282 when, in the Sicilian Vespers, Sicily revolted and turned to the house of Aragon. From thereafter Sicily and Naples became different states.