In the Early Middle Ages, through barbarian movements and the waning of Roman (by this time Byzantine) authority, the island fell out of the sphere of influence of any higher government, though it retained its Byzantine Greek culture for centuries. Saracen raids provided an impetus for the creation of independent, quasi-royal giudicati in the eighth through tenth centuries. Only in the late eleventh century do these entities come into increased contact with western Europe and Christendom. Falling under papal influence, Sardinia becomes the focus of the rivalry of Genoa and Pisa and finally of the local population and the Crown of Aragon, which subsumed the island as the Kingdom of Sardinia (1298), which was to last, in some form or other, until then being incorporated into the Kingdom, later Republic, of Italy.
The first humans to settle in Gallura and Northern Sardinia probably came from Italian peninsula, possibly from Tuscany. The central region may have been populated by people arriving from the Iberian Peninsula through the Balearic Islands. In 1979 human remains were found that were dated to 150,000 BC. In 2004, in a cave in Logodoru a human finger bone was found that was dated up to 250,000 BC.
Prehistoric arrowheads (3rd millennium BC) and figurines (now in the Archeological Museum of Cagliari) were retrieved which demonstrate a well developed industry of stone carving. Already in the Stone Age, Monte Arci played an important role. The old volcano was one of the central places where obsidian was found and worked for cutting tools and arrowheads. Even now the volcanic glass can be found on the sides of the mountain. The Archeological Museum of Sassari displays ceramics from the Copper or Aneolithic Age (2600 BC).
It is known that the Sardinians already had contact with the Myceneans, who traded with the West Mediterranean. Contact with powerful cities of Crete, such as Kydonia, is clear from pottery recovered in archaeological excavations in Sardinia. The alleged connection with the Shardana, the sea people that invaded Egypt has not been proven but very likely. Euboeans, the first Greeks to navigate westwards, called the island Hyknousa (later Latinized in Ichnus(s)a). The Nora stone has been seen as proof that the island was called Sharden by the Phoenicians, and from there it derived the name Sardinia.
A revolt, led by two Sardo-Punic nobles, broke out after the crushing Roman defeat at Cannae (216 BC). A Roman army of 23,000 men, under Titus Manlius Torquatus, met the Carthagianian-Sardinian allied forces in the south of the island, defeating them and killing 12,000 men. The so-called Sardi Pelliti ("Fur-covered Sardinians") living in the impervious mountains of the interior resisted the Roman colonization for more than a century, Marcus Caecilius Metellus subduing them only in 127 BC.
Under Roman domination, Latin became the speech of the majority of the inahbitants, ultimately developing in to the Sardinian language. The Phoenician-Punic culture remained very strong under the Romans until the first centuries AD. Tharros, Nora, Bithia, Antas and Monte Sirai are now important archaeological monuments where architecture and city planning can be studied.
During the Roman period, the geographer Ptolemy noted that Sardinia was inhabited by the following peoples, from north to south: the Tibulati and the Corsi, the Coracenses, the Carenses and the Cunusitani, the Salcitani and the Lucuidonenses, the Æsaronenses, the Æchilenenses (also called Cornenses), the Rucensi, the Celsitani and the Corpicenses, the Scapitani and the Siculensi, the Neapolitani and the Valentini, the Solcitani and the Noritani.
In 534 the small Vandal forces surrendered immediately to the Byzantines when news of the Vandal collapse; thenceforth the island was part of the Byzantine Empire, included in the African prefecture. The local governor sat in Caralis. During the Gothic Wars much of the island fell easily to the Ostrogoths, but an army sent from Carthage and the final fall of German resistance in the mainland reassured the Byzantine control.
One of the few ethnic Sardinians known from this period was one Ospitone, a leader of the Barbaricini (people of Barbagia). He was a Christian, which was apparently still unusual on Sardinia, in the time of Gregory the Great.
Starting from 705–706, the Saracens from North Africa (recently conquered by the Arab armies) harassed the population of the coastal cities. News about the political situation of Sardinia in the following centuries is scarce. Due to Saracen attacks, in the 9th century Tharros was abandoned in favor of Oristano, after more than 1800 years of occupation; Caralis and numerous other coastal centres suffered the same fate. There was news of another massive Saracen sea attack in 1015 from Spain, led by Mujahid (Latinized in Museto), who established a colony in the north in 1018-1028. Pope Benedict VIII asked the aid of the maritime republics of Pisa and Genoa in the struggle against the Arabs.
At the dawn of the judicial era Sardinia had some 330,000 inhabitants, of which 120,000 were free. These were subjected to the authority of local curators (administrators), in turn subjected to the judge (who also administrated justice and was the commander of the army). The church was also powerful, and at this time it had completely abandoned the Eastern Rite. The late eleventh century arrival of Benedictine, Camaldolese and other monks from the Mezzogiorno, Lombardy, and Provence, especially the monasteries Montecassino, Saint-Victor de Marseille, Vallombrosa, boosted the agriculture in a land which was extremely underdeveloped. The Condaghi (catalogues, cartularies) of the monasteries, which record property transactions, are an important source for the study of the island in the eleventh and twelfth centuries. Evidence from the Condaghi of San Pietro di Sili and Santa Maria di Bonarcado concerning the children of slaves has been adduced to show that differences in agricultural lifestyles between regions may affect the survival rate of females, hypothetically through increased infanticide of baby girls. The abbacy of Santa Maria di Bonarcado contained more central, upland regions where a pastoral economy dominated and women were less economically useful; among children in that region, sex ratios are highly skewed in favour of men. On the other hand, in the region of San Pietro di Sili, less pastoral, child sex ratios are not skewed abnormally.
There were five (historically known) Giudicati: Agugliastra, Logudoro, Cagliari, Arborea and Gallura. Agugliastra was early on absorbed by Cagliari and Arborea and Logudoro (and perhaps Gallura) were united for a time in the eleventh century.
The initiatives of the Gregorian reformers led to greater contact between Sardinia and the continent, especially through the desires of the judges to establish monasteries with monks from continental monasteries at Montecassino and Marseille. By the twelfth century, the Sardinian Giudicati, though obscure, are visible through the mists of time. They professed allegiance to the Holy See, which put them under the authority of the Archdiocese of Pisa, superseding the ancient primacy of the Archdiocese of Cagliari on the island. Some historians have even hypothesised that Sardinia was more or less a theocracy under the Cagliaritan diocese until their power was replaced by the Pisan.
Often warring between one another, the Giudicati made a great number of commercial concessions to the Pisans and the Genoese. The Repubbliche Marinare soon became the true masters of the Sardinian economy.
In the late twelfth and early thirteenth centuries, all four Giudicati passed to foreign dynasties and the local families were relegated to minor positions. Arborea passed to the Catalan House of Cervera (Cervera-Bas) in 1185, though this was contested for the next few decades. In 1188, Cagliari was conquered by the House of Massa from the Republic of Pisa. Gallura became by marriage — it had been inherited by a woman, Elena — a possession of the House of Visconti, another Pisan family, in 1207. Only Logudoro survived to the end under local Sardinian rulers. However, its end was early. It passed to Genoa in 1259 after the death of its last judge (Giudicessa), Adelasia, only a year after the Pisans deposed the last ruler of Cagliari. Gallura survived longer, but the enemies of the Visconti in Pisa soon removed the last judge, Nino, a friend of Dante Alighieri, in 1288.
About the same time, Sassari declared itself a free commune allied to Genoa. In the early fourteenth century, much of Eastern Sardinia was under Pisan authority. Arborea, however, survived until 1420. The most remarkable Sardinian figure of the Middle Ages, Eleanor of Arborea, was co-ruler of that region in the late 14th century; she laid the foundations for the laws that remained valid until 1827, the Carta de Logu.
The watchtowers all along the coast are called Catalan Towers and served to protect the island against the Arab incursions. Some of these towers were built with the stones of the Phoenician cities because they lay on strategic sites. A nice example of re-use for secular and ecclesiastical architecture can also be found in the church of Santa Giusta where the old city of Othoca had been.
The loss of the independence, the firm Catalan (later Spanish) rule, with the introduction of a sterile feudalism, as well as the discovery of the Americas, provoked an unstoppable decline of Sardinia. A short period of resurgence occurred under the local noble Leonardo Alagon, marquess of Oristano, who managed to defeat the viceroyal army in the 1470's but was later crushed at the Battle of Macomer (1478), ending any further hope of independence for the island. The unceasing attacks from North African pirates and a series of plagues (from 1582, 1652 and 1655) further worsened the situation. In 1637 a French fleet sacked Oristano.
Until the Unification of Italy in 1861, Sardinia and Piedmont were joined in the Kingdom of Sardinia. In 1802 King Victor Emmanuel I was ousted from Piedmont by the French army, and four years later moved his court to Cagliari: the brief Republic declared that year, soon thwarted by the Savoy army, was the sole concrete attempt of independence from the Sardinians. The King returned to Turin in 1814. In the early 19th century the situation of the island was the following: 99% of illiterates, absence of any developed economy or trade, cities and forests abandoned. The development of the infrastructure was slow, as the Piedmontese initially did little to improve the conditions of the population. Under King Carlo Felice, a main road, still bearing his name, was built from south (Cagliari) to north (Sassari), while the universities of the two centres were enhanced; however, the few riches remained in the hands of a restricted number of barons and clergymen, banditism attracted a large number of inhabitants, and the force of immigration of Corsi, Ligurians and Maltese could do little to solve the demographics void. The concession to Sardinia of the same rights of Piedmont in 1847, under King Charles Albert, was of little help.
In 1883 the first trains travelled between Cagliari and Sassari and under Mussolini the swamps around Oristano were laid dry and the foundation of the most successful agrarian community was laid, Arborea. Mussolini also founded Carbonia, the centre of the mining activity. In 1927 the province of Nuoro was created, and works to dry the numerous waste lands favoured the arrival of immigrants. World War II saw Sardinia as the theater of minor activities, but the main event was the successful fight against malaria, obtained also with the help of the Rockefeller Foundation. Sardinia was declared an autonomous region, with some special tax raising and cultural privileges, in 1947. First regional elections were held on may 8, 1949.
After the war coal decreased in importance and that of tourism increased. Many efforts to create jobs have failed because of the high costs of transport that could not compensate the cheap labor.
Today Sardinia's history is still visible in language and culture. Noticeable is also the difference between coastal regions and the inland. Coastal regions have always been more open to outside influences. Nowadays Sardinia is most known for the east-northern coasts and island (La Maddalena, Costa Smeralda), the west-northern coast near Sassari (Alghero, Stintino, Castelsardo) and Cagliari, because these are easily reached by ship and by plane.