At the beginning of the 9th century in fact, under the patronage of the Papal Court, that was then ruled by Benedict XIII, in Sardinian history the two Maritime republics of Genoa and Pisa, that were at first allied against the Muslim emir Musa who had taken possession of some areas of the island, were afterwards competing for the dominion on the weak judge states. The defiance ended up in favour of Pisa. The peace of 1087AD between Genoese and Pisans brought, during the period that immediately precedes the Aragonese conquest, the predominance of Pisa across the whole of Sardinia.