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.
History of Cagliari
In the year 753 AD, Arab sources report the imposition of the jizya, a tax for those not converted to Islam, the dhimmi, on the Sardinians. This presumes the occupation of the land on which it is imposed, but the lack of further sources suggests ephemeral occupation and control confined to some coastal regions. On this occasion, however, the Arabs could have imposed the dismantling of the defenses of the city. When in 827 the Muslim conquest of Sicily began, contacts with Constantinople became extremely difficult. The few available sources suggest that the richest and most influential family of the island began to take over the local government. Although a vassal of the Byzantines, so that even at the beginning of the eleventh century its rulers still boasted the title of imperial "protospatharios", Sardinia was in fact independent. Cagliari became the capital of this independent kingdom or "giudicato", ruled by a "judice" (literally "judge" or magistrate). However, there is some evidence that during this period of independence from external rule the city was reduced to a small port community because it was too exposed to attacks from the sea by Moorish pirates. Apparently many people left Caralis and founded a new town (named Santa Igia) in an area close to the Santa Gilla swamp to the west of Cagliari, but relatively distant from the sea. At the present state of research, the site of historic Santa Gilla has not yet been identified, because it was completely destroyed by the Pisans in the thirteenth century. The walls were dismantled, as well as the cathedral and the palace of the "judice".