Kingdom of Sardinia
On 17 March 1861, law no. 4671 of the Sardinian Parliament proclaimed the Kingdom of Italy, so ratifying the annexations of all other Apennine states, plus Sicily, to the Kingdom of Sardinia. The institutions and laws of the Kingdom were quickly extended to all of Italy, abolishing the administrations of the other regions. Piedmont became the most dominant and wealthiest region in Italy and the capital of Piedmont, Turin, remained the Italian capital until 1865, when the capital was moved to Florence. But many revolts exploded throughout the peninsula, especially in southern Italy, and on the island of Sicily, because of the perceived unfair treatment of the south by the Piedmontese ruling class. The House of Savoy ruled Italy until 1946 when Italy was declared a republic by referendum. In this referendum the southern regions, including Sardinia, voted overwhelmingly in favor of the House of Savoy, with the results being 63.8% in favor of maintaining the monarchy.
Norman conquest of southern Italy
Although the conquest of Sicily was primarily military, Robert and Roger also signed treaties with the Muslims to obtain land. Hindered by Sicily's hilly terrain and a relatively small army, the brothers sought influential, worn-down Muslim leaders to sign the treaties (offering peace and protection for land and titles). Because Sicily was conquered by a unified command, Roger's authority was not challenged by other conquerors and he maintained power over his Greek, Arab, Lombard and Norman subjects. Latin Christianity was introduced to the island, and its ecclesiastical organisation was overseen by Roger with papal approval. Sees were established at Palermo (with metropolitan authority), Syracuse and Agrigento. After its elevation to a Kingdom of Sicily in 1130, Sicily became the centre of Norman power with Palermo as capital. The Kingdom was created on Christmas Day, 1130, by Roger II of Sicily, with the agreement of Pope Innocent II, who united the lands Roger had inherited from his father Roger I of Sicily.
These areas included the Maltese Archipelago, which was conquered from the Arabs of the Emirates of Sicily; the Duchy of Apulia and the County of Sicily, which had belonged to his cousin William II, Duke of Apulia, until William's death in 1127; and the other Norman vassals.