The ambition of the Normans under leadership of the d'Hauteville brothers was fuelled, not sated, by their success in establishing a principality in southern Italy in the mid-1000s. As a result, they were eager, with modest encouragement from the Papacy, to extend their empire to Saracen-ruled Sicily under the banner of Christendom.

In 1060 the Norman leader Robert Guiscard with his brother Roger d'Hauteville opened their invasion of Sicily. The Normans first stormed and captured Messina, that traditional stepping stone from the Italian mainland into Sicily. In subsequent years, aided by dissension among the Saracens and supported by elements of the indigenous Greek population, the Norman invaders fought their way across northern Sicily. They captured the Saracen capital of Palermo ten years later, in 1071. The tide of war in eastern Sicily seesawed back and forth, with major cities taken and then retaken by the contending forces. Finally, in 1090 the last Saracen stronghold fell, and the Normans were left in complete control of the entire island.

The two powerful d'Hauteville brothers demonstrated a skill in governance that was equal to their skill in warfare. Robert and Roger established an amicable arrangement between themselves for allocating captured spoils and dividing power. That agreement left Robert as ruler of southern Italy and Roger as ruler of Sicily. Following the deaths of Robert (1085) and Roger (1101), relations in the next generation were less peaceable. Roger was first succeeded as Count of Sicily by his older son Simon, who died three years later while still a minor. Roger's younger son, another Roger, succeeded to the realm and--upon reaching maturity--weathered an extended period of hostility with various changing alliances among his mainland cousins, the Papacy and other Italian princes. Finally he succeeded in uniting Sicily and the d'Hauteville territory on the mainland into a single powerful kingdom--known initially as the Kingdom of Sicily, Apulia and Calabria, and later as the Kingdom of Two Sicilies. As Roger I, he was crowned king of the new realm in 1130.

On the island of Sicily the d'Hautevilles introduced a period of remarkable tolerance, with even-handed treatment of the Greek and Saracen populations, who were joined by an increasing migration of new settlers from the Italian mainland. The Norman dynasty, however, was to be only a brief interlude before Sicily became a chip in the high-stakes game of European politics.