At that time, the city was a very important commercial centre and controlled a significant Mediterranean merchant fleet and navy. It expanded its powers in 1005 through the sack of in the south of Italy. Pisa was in continuous conflict with some 'Saracens' - a medieval term to refer to Arab Muslims - who had their bases in Corsica, for control of the Mediterranean. In 1017, Sardinian Giudicati were militarily supported by Pisa, in alliance with Genoa, to defeat the Saracen King Mugahid, who had settled a logistic base in the north of Sardinia the year before. This victory gave Pisa supremacy in the Tyrrhenian Sea. When the Pisans subsequently ousted the Genoese from Sardinia, a new conflict and rivalry was born between these major marine republics. Between 1030 and 1035, Pisa went on to defeat several rival towns in Sicily and conquer Carthage in North Africa. In 1051–1052, the admiral Jacopo Ciurini conquered Corsica, provoking more resentment from the Genoese. In 1063, Admiral Giovanni Orlandi, coming to the aid of the Norman Roger I, took Palermo from the Saracen pirates. The gold treasure taken from the Saracens in Palermo allowed the Pisans to start the building of their cathedral and the other monuments which constitute the famous .