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.
Flag of Sardinia
Before the Kingdom of Sardinia was founded, the rulers of the island were known as archons (ἄρχοντες in Greek) or judges ("iudices" in Latin, "judikes" in Sardinian, "giudici" in Italian). The island was organized into one "judicatus" from the 9th century on (see List of monarchs of Sardinia). After the Muslim conquest of Sicily in the 9th century, the Byzantines, who previously ruled Sardinia, couldn't manage to defend their far west province. Probably, a local noble family acceded to power, still identifying themselves as vassal of the Byzantines, but independent "de facto", as communications with Constantinople were very difficult. At the beginnings of the 11th century an attempt to conquer the island was made by Spanish Muslims. We have very little record of that war, only by Pisa and Genoa chronicles. Christians won, but after that, the previous Sardinian kingdom was totally undermined and divided into four more little judicati: Cagliari, Arborea, Gallura, and Torres or Logudoro; each one developed its own coat of arms. When, with the appointment of the King of Aragon as King of Sardinia, the island again became one united kingdom, only the Judicatus of Arborea survived, and fought for a century against the Kingdom of Sardinia for supremacy.