The invasion of Tunisia was probably prompted by the piratical raids of Mahdia's rule Tamin in Italian waters, as well as his involvement in southern Italy fighting the Norman invasion.
Greed also motivated the invasion; promised plunder was immense. There was also an ideological element to the invasion; the indulgences granted by the Pope to the League and their fighting under the banner of Saint Paul would lead the invasion of Tunisia to be classified as a crusade by later historians.
The Crusade was backed by Matilda of Tuscany and led by Hugh of Pisa.
Pantaleone of Amalfi and his forces attacked Mahdia in later 1087, taking the Zirids by surprise. Although the city was captured, the Italians decided they did not have the forces to hold it, and sacked the town. The Zirid fleet had been captured in the harbour when Mahdia fell; those vessels that could not be crewed by the Italians and used to carry plunder were put to the torch, breaking the Zirid naval strength. The Amalfi-Pisan fleet then sailed for Palmero, where the plunder was deposited for safekeeping and their forces augmented.The Genoans had not joined Pantaleone in Mahdia, but had instead moved to protect the city of Carthage, which they had previously held only through paying massive annual tribute to the Zirids. A Zirid attack was narrowly thwarted before the attack on Mahdia forced the Zirids to recall some forces south. Once the Italians withdrew from Mahdia, the Zirid army was due to return north. Genoan ships however harried the coast, launching lightning raids and looting and burning unfortunate towns. Believing these attacks indicated Mahdia was still not secure, the Zirids divided their forces, buying the League time to bring the bulk of its forces back across the sea. ===1088=== When the League's forces returned in early 1088 and captured Tunis, the Zirids broke entirely; lacking a single leader and unable to move their troops by sea, they had not choice but to disband. Italian forces spent the remainder of the year asserting their control of remaining coastal towns.
Many minor Italian nobles were granted conquered lands, and plunder was significant. Bedouin Emirates remained inland after the conquest; treaties were signed with these former enemies of the Zirids to help secure the Carthaginian March. Pantaleone was named Dux of Carthage.
The League was increasingly rich and prestigious due to its conquests. Having near-complete dominion over the western Mediterranean and monopolies on trade, the cities of Amalfi, Genoa and Pisa boomed.