Mujāhid al-‘Āmirī, ruler of the Muslim taifa of Denia, is probably motivated to conquer Sardinia in order to legitimize his power in Denia and the Balearics.
A civil war (fitna) had broken out between various factions (taifas) after 1009 in the declining caliphate.
A freed slave, Mujāhid had found it necessary to legitimize his position by appointing a puppet caliph, ‘Abd Allāh ibn ‘Ubayd Allāh ibn Walīd al-Mu‘iṭī, in 1013.
He probably saw an opportunity to secure his authority by waging a holy war (jihād), a device which had been used effectively by the man who appointed Mujāhid to rule Denia, al-Manṣūr.
The conquest of Sardinia is thus undertaken in the name of al-Mu‘iṭī, and the Islamic historian Ibn al-Khatīb praises Mujāhid before God for his piety in the event.
One school of Islamic jurisprudence, represented in Mujāhid's day by al-Mawardī, recognizes "emirs by conquest", those like Mujāhid who have a right to rule lands they conquer for Islam.In 1015, Mujāhid comes to Sardinia with one hundred and twenty ships, a large number that confirms that the expedition was not designed for raiding.
The twelfth-century Pisan Liber maiolichinus, a history of the 1113–1115 Balearic Islands expedition, records that Mujāhid controlled all of the Sardinian coastal plain.
In the Pisan histories of the tim,e the expedition to Sardinia of 1015 is described tersely: "the Pisans and Genoese made war with Mujāhid in Sardinia, and defeated him by the grace of God" and "the Pisans and Genoese defended Sardinia."
The account of the Liber maiolichinus is more detailed, although it excludes the Genoese, and so is probably referring to the 1015 expedition.
It reports that even the Pisan nobles, in their eagerness, took turns rowing the galleys.
It also compares them to starving lions rushing their prey.
Mujāhid flees at the approach of the Italians, according to the Liber, which does not mention an actual engagement in 1015.