 With the aid of reinforcements from Ifriqiya and al-Andalus, in 831 they took Palermo, which became the capital of the new Muslim province.The Byzantine government sent a few expeditions to aid the locals against the Muslims, but preoccupied with the struggle against the Abbasids on their eastern frontier and with the Cretan Saracens in the Aegean Sea, it was unable to mount a sustained effort to drive back the Muslims, who over the next three decades raided Byzantine possessions almost unopposed.The strong fortress of Enna in the centre of the island was the main Byzantine bulwark against Muslim expansion, until its capture in 859.