"From this [prefecture], with the help of God, seven provinces with their judges will depend, of which Zeugi, which was previously called Proconsular Carthage, Byzacium and Tripoli will have consulares as governors; while the others, namely Numidia, Mauritania and Sardinia will be, with the help of God, governed by praesides".»[2] Despite the new establishment, the Byzantines had the fight with the Barbaricini, who had control of the interior of the isle.

[3] The dux of Sardinia, who had the task of fighting against the Barbaricini, had his residence in the mountains of Barbagia, where this people lived, reluctant to allow themselves to be subjugated.

[6] The magister militum per Africam, John Troglita attempted to recover it, but was defeated by the Goths [1] "Now, Totila desired to seize the islands belonging to Libya.

The invasion of the Italian peninsula by the Longobards in 568, which changed the face of Italy, only resulted in a few coastal raids on Sardinia, even if there are traces of their presence on the island, documented by the discovery of various objects, including numerous coins.

During the pontificate of Pope Gregory I (590-604), Sardinia was included within the Roman sphere, participating in the work of protection, administration and evangelization of this pontiff.He wrote numerous letters dedicated to Sardinian dignitaries.

They shown the continued division of Sardinia into a Romanized zone (coasts and coastal cities, plain) and a still barbaric internal region, Barbagia.

It was discovered that the Iudex Provinciae of Sardinia, in order to recover the money lost to purchase the governorship, was allowing pagans to continue worshiping their idols in exchange for paying a tax: [10] "Learning that many of the natives of Sardinia still... make sacrifices to idols..., I sent one of the bishops of Italy, who... converted many of the natives.

And, when some were baptized and stopped making sacrifices to idols, the said governor of the island continued to demand payment of the tax... And, when said bishop spoke with him, he responded that he had promised him a suffrage.

[14] In 815, ambassadors from Sardinia went to the Carolingian Empire, with gifts to Emperor Louis the Pious, possibly to request military assistance against the Arab attacks.

[15] Later, in 829, the Count Bonifacio (Carolingian feudal lord in charge of defense of Corsica) arrived in Sardinia, searching for help from Sardinian authorities for his counterattack of the Arab pirates in the African coasts.

We have thought to beg your highness to deign to send us, as many as your magnificence sees fit, Sardinians, adults or young men with their weapons, who might be able to carry out for us every day orders.

"[16]Later pontifical letters until the eleventh century would show the gradual reduction of the institutional and political importance of the iudices in the eyes of the popes.

[14] From the pontifical letters of Pope Nicholas I (858–67) and John VIII to Sardinia, it isn't clear if the island was divided at this point or a central authority remained in the island, but an increasing consensus saw that a supreme ruler of Sardinia (the archon) had supremacy over local principes as local archontes.

[17] The Byzantium Emperor Constantine VII named the ruler of Sardinia (a nominal and autonomous vassal at this time) as archon in his book De Cerimoniis (956–959 AD).

"[19]The archontate is also attested in local inscriptions in churches from the end of the tenth century (naming some archons as Torchotorio and Salousio) [20] and some seals from the period.

[23] Contacts between Sardinia and Byzantium are attested as later as 1006, when envoys of the emperor Basil II arrived at the port of Medinaceli with some Andalusi sailors who had been captured on the Sardinian and Corsican coasts.

[24] In the years 1015 and 1016, the ruler of the taifa of Dénia, Mujahid al-Amiri, launched a major invasion of Sardinia, intending to conquer it.

[25] Muhajid ruled the isle for a year and only a joint expeditions from the maritime Republic of Pisa and Genoa repelled the invaders.

A dux was responsible for military matters and was based at Fordongianus (Forum Traiani), which since Roman times had been a fortified bastion against the inhabitants of the Barbagia.

Some of the island's garrison soldiers were caballarii (horsemen) and received in compensation for their military services land parcels to farm.

After the fall of the African Exarchate in the 7th century, caused by the Arab conquest of Carthage, the ducatus was directly dependent on Constantinople.

The governors of the island originally held the rank of hypatos and later that of protospatharios, before receiving the title of patrikios from the middle of the ninth century.