During the 820s, the Byzantine Empire suffered two great losses that destroyed their naval supremacy in the Mediterranean: the beginning of the Muslim conquest of Sicily and the conquest of Crete to Andalusian exiles. These losses ushered in an era where Saracen pirates raided the Christian northern shores of the Mediterranean almost at will. The establishment of the Emirate of Crete, which became a haven for Muslim ships, opened the Aegean Sea up for raids, while their—albeit partial—control of Sicily allowed the Arabs to raid and even settle in Italy and the Adriatic shores. Several Byzantine attempts to retake Crete in the immediate aftermath of the Andalusian conquest, as well as a large-scale invasion in 842/43, failed with heavy losses.
