In 510 BC, Sardinia passed into the hands of Carthage, the powerful colony founded by the Phoenicians on the shores of northerner Africa, in active trading and launched in the Mediterranean to become an economic power and military policy.

In 509 a.C. after years of struggle, the Carthaginian led by general Hamilcar and Asdrubal managed to occupy the island due to the division of Sardis. Sardinia was a major hub of an extensive network: cereals, craft items, minerals were shipped towards the most important cities of the Mediterranean. In this distinguished market Tharros, was the richest city in the island.

In 238 a.C. Romans took possession of Sardinia. At the beginning there were many troubles caused by the resistance of the Sardinian-Punic peoples, culminating in the failed revolt of Ampsicora, a powerful landowner Sardinian-Punic in 215a.C.. Sardinia Roman remain culturally tied to the long cultural traditions Punic.

In 227a.C. the island became a Roman province, was placed under the government administration, judicial and military of a magistrate and was forced to pay heavy taxes. The Roman conquest did not revolutionize the economic life, the only novelty was that next to latifundias private, partly to let Sardo-Punic and partly awarded to families of the Roman nobility, was established a latifundium public administrators assigned to private individuals for the cereal production needed to meet the Roma and the Peninsula.

In 534 Justinian, Emperor of the East, wanting to regain the western part of the empire, started a war with the Vandals. With his victory all domains of vandalism, and between these Sardinia, came to be part of the Byzantine Empire.

Under the rule of Byzantium, Sardinia experienced a long period of peace but not prosperity: it was the margin of the empire and the presence of the capital was felt only through the strict and heavy taxes. Sardinia was ruled by a headmaster and a dux, the first residing in Cagliari and had administrative duties civil laws adopted, was responsible for Justice and taxes on the island.

The separation of Byzantium from Sardinia and the need for the Sardinians to organize a defense against its Arab danger, were probably behind the birth of the Giudicati. Towards the end of the VIII century. Bisanzio gradually abandoned the island to its fate.

The powers of the two magistrates who ruled the Byzantine Sardinia, the dux and the headmaster, were concentrated in the hands of a single authority which, in turn, delegated the power to four magistrates residing in different parts of the isle. Sardinia was divided into areas that, over time, became autonomous with respect to the central power and gave the Byzantine administrative institutions and their policies: thus arose the four Giudicati of Cagliari, Torres, Arborea and Gallura.