In 1720, the island and its kingdom were ceded by the Habsburg and Bourbon claimants to the Spanish throne to the Duke of Savoy, Victor Amadeus II.

The Congress of Vienna (1814–1815), which restructured Europe after Napoleon's defeat, returned to Savoy its mainland possessions and augmented them with Liguria, taken from the Republic of Genoa.

In 1847–1848, through an act of union analogous to the one between Great Britain and Ireland, the various Savoyard states were unified under one legal system with their capital in Turin, and granted a constitution, the Statuto Albertino.

Facing Arab attempts to sack and conquer, while having almost no outside help, Sardinia used the principle of translatio imperii ("transfer of rule") and continued to organize itself along the ancient Roman and Byzantine model.

The island was not the personal property of the ruler and of his family, as was then the dominant practice in western Europe, but rather a separate entity and during the Byzantine Empire, a monarchical republic, as it had been since Roman times.

Due to Saracen attacks, in the 9th century Tharros was abandoned in favor of Oristano, after more than 1800 years of occupation; Caralis, Porto Torres, and numerous other coastal centres suffered the same fate.

Before the Kingdom of Sardinia and Corsica, the archons (Ancient Greek: ἄρχοντες), or judices in Latin,[18][19] who reigned in the island from the 9th or 10th century until the beginning of the 11th century, can be considered real kings of all Sardinia (Κύριε βοήθε ιοῦ δούλου σου Tουρκοτουρίου ἅρχωντοσ Σαρδινίας καί τής δούλης σου Γετιτ),[20][21][22] even though nominal vassals of the Byzantine emperors.

Of these sovereigns, only two names are known: Turcoturiu and Salusiu (Tουρκοτουρίου βασιλικοῦ πρωτοσπαθαρίου[23] (καὶ Σαλουσίου των εὐγενεστάτων ἀρχόντων),[24][25] who probably ruled in the 10th century.

[26] The realm was divided into four small kingdoms, the Judicates of Cagliari, Arborea, Gallura and Logudoro, perfectly organized as was the previous realm, but was now under the influence of the papacy, which claimed sovereignty over the entire island, and in particular of the Italian states of Genoa and Pisa, that through alliances with the "judges" (the local rulers), secured their political and economic zones of influence.

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 Treaty of Anagni.

There were other reasons beside this papal decision: it was the final successful result of the long fight against the Ghibelline (pro-imperial) city of Pisa and the Holy Roman Empire itself.

In 1297, Pope Boniface VIII, intervening between the Houses of Anjou and Aragon, established on paper a Regnum Sardiniae et Corsicae that would be a fief of the papacy.

Then, ignoring the indigenous states which already existed, the Pope offered his newly created fief to James II of Aragon, promising him papal support should he wish to conquer Pisan Sardinia in exchange for Sicily.

In 1420, Alfonso V of Aragon, king of Sicily and heir to Aragon, bought the remaining territories for 100,000 gold florins of the Judicate of Arborea in the 1420 from the last judge, William III of Narbonne, and the Kingdom of Sardinia extended throughout the island, except for the city of Castelsardo (at that time called Casteldoria or Castelgenovese) that was stolen from the Doria in 1448, and renamed Castillo Aragonés (Aragonese Castle).

Although the Kingdom of Sardinia and Corsica could be said to have started as a questionable and extraordinary de jure state in 1297, its de facto existence began in 1324 when, called by their allies of the Judicate of Arborea in the course of war with the Republic of Pisa, James II seized the Pisan territories in the former states of Cagliari and Gallura and asserted his papally-approved title.

Threatened by the Aragonese claims of suzerainty and consolidation of the rest of the island, in 1353 Arborea, under the leadership of Marianus IV, started the conquest of the remaining Sardinian territories, which formed the Kingdom of Sardinia.

After the sale of the remaining territories for 100,000 gold florins to the Judicate of Arborea in 1420, the Kingdom of Sardinia extended throughout the island, except for the city of Castelsardo (at that time called Casteldoria or Castelgenovese), which had been stolen from the Doria in 1448.

By the Treaty of Utrecht (1713), Spain's European empire was divided: the House of Savoy received Sicily and parts of the Duchy of Milan, while Charles VI (the Holy Roman Emperor and Archduke of Austria), received the Spanish Netherlands, the Kingdom of Naples, Sardinia, and the bulk of the Duchy of Milan.

Because the Kingdom of Sardinia had existed since the 14th century, the exchange allowed Victor Amadeus to retain the title of king in spite of the loss of Sicily.

During the Savoyard period as a composite state, Italian, which alongside French had already been made official in the peninsula since the 16th century via the Rivoli Edict,[36][37][38] was introduced to Sardinia in 1760.

The Kingdom of Sardinia's attempt of promotion of a unitary language was incisive,[40] and also the replacement of Spanish with Italian has been described as a "revolution of ideas".

The island of Sardinia stayed out of the reach of the French for the rest of the war and was, for the first time in centuries governed directly by its king instead of a viceroy.

[45] Earlier in 1847, the island of Sardinia, a Piedmontese dependency for more than a century, lost its own residual autonomy to the peninsula through the Perfect Fusion issued by Charles Albert.

As a result, the kingdom's fundamental institutions were deeply transformed, assuming the shape of a constitutional and centralized monarchy on the French model; under the same pressure, Charles Albert declared war on Austria.

After a short and disastrous renewal of the war with Austria in 1849, Charles Albert abdicated on 23 March 1849 in favour of his son Victor Emmanuel II.

In 1852, a liberal ministry under Count Camillo Benso di Cavour was installed and the Kingdom of Sardinia became the engine driving Italian unification.

The Kingdom of Sardinia took part in the Crimean War, allied with the Ottoman Empire, Britain, and France, and fighting against Russia.

Following the bloody battles of Magenta and Solferino, both French victories, Napoleon thought the war too costly to continue and made a separate peace behind Cavour's back in which only Lombardy would be ceded.

This alarmed Napoleon III, who feared a strong Savoyard state on his south-eastern border and he insisted that if the Kingdom of Sardinia were to keep the new acquisitions they would have to cede Savoy and Nice to France.

Eventually, King Charles Albert of Savoy adopted from Revolutionary France the Italian tricolor, surmounted by the Savoyard shield, as his flag.