History of Sardinia
In the Early Middle Ages, through barbarian movements, the waning of the Byzantine Empire influence in the western Mediterranean and the Saracen raids, the island fell out of the sphere of influence of any higher government. This led to the birth of four kingdoms called "Judicates" (Latin: "Judicati"; Sardinian: "Judicados") in the 8th through 10th centuries. Falling under papal influence, Sardinia became the focus of the rivalry of Genoa and Pisa, the Judicates and the Crown of Aragon, which eventually subsumed the island as the Kingdom of Sardinia in 1324. The Kingdom was to last until 1718, when it was ceded to the Piedmontese House of Savoy; later, in 1861, it would thus become the Kingdom of Italy and finally in 1946 the Italian Republic.
Italy
In the south, Sicily had become an Islamic emirate in the 9th century, thriving until the Italo-Normans conquered it in the late 11th century together with most of the Lombard and Byzantine principalities of southern Italy. Through a complex series of events, southern Italy developed as a unified kingdom, first under the House of Hohenstaufen, then under the Capetian House of Anjou and, from the 15th century, the House of Aragon. In Sardinia, the former Byzantine provinces became independent states known in Italian as Giudicati, although some parts of the island became controlled by Genoa or Pisa until the Aragonese annexation in the 15th century. The Black Death pandemic of 1348 left its mark on Italy by killing perhaps one third of the population. However, the recovery from the plague led to a resurgence of cities, trade and economy which allowed the bloom of Humanism and Renaissance, that later spread to Europe.