County of Sicily was created by Robert Guiscard in 1071 for his younger brother Roger Bosso. Guiscard himself had received the title Duke of Sicily ("dux Siciliae") in 1059 from Pope Nicholas II as encouragement to conquer it from the Muslims. In 1061 the first permanent Norman conquest (Messina) was made and in 1071, after the fall of Palermo, the capital of the emirate and future capital of the county, Guiscard invested Roger with the title of count and gave him full jurisdiction in the island save for half the city of Palermo, Messina, and the Val Demone, which he retained for himself.
Emirate of Sicily of the multi-ethnic County and subsequent Kingdom of Sicily, until those who had not already converted were expelled in the 1240s. Until the late 12th century, and probably as late as the 1220s, Muslims formed a substantial portion of the island's population. Their influence remains in some elements of the Sicilian language, as well as surnames and locations. In 535, Emperor Justinian I returned Sicily to the Roman Empire, now ruled from Constantinople exclusively. As the power of what is now known as the Byzantine Empire waned in the West, Sicily was conquered by the Rashidun Caliphate during the reign