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.
Kingdom of Sardinia
The Kingdom of Sardinia and Corsica (later, just the "Kingdom of Sardinia" from 1460) was a state whose king was the King of Aragon, who started to conquer it in 1324, gained full control in 1410, and directly ruled it until 1460. In that year it was incorporated into a sort of confederation of states, each with its own institutions, called the Crown of Aragon, and united only in the person of the king. The Crown of Aragon was made by a council of representatives of the various states and grew in importance for the main purpose of separating the legacy of Ferdinand II of Aragon from that of Isabella I of Castile when they married in 1469. The idea of the kingdom was created in 1297 by Pope Boniface VIII, as a hypothetical entity created for James II of Aragon under a secret clause in the Treaty of Anagni. This was an inducement to join in the effort to restore Sicily, then under the rule of James's brother Frederick III of Sicily, to the Angevin dynasty over the oppositions of the Sicilians. The two islands proposed for this new kingdom were occupied by other states and fiefs at the time. In Sardinia, three of the four states that had succeeded Byzantine imperial rule in the 9th century had passed through marriage and partition under the direct or indirect control of Pisa and Genoa in the 40 years preceding the Anagni treaty. Genoa had also ruled Corsica since conquering the island nearly two centuries before ("c". 1133).