In AD 673, a large army consisting of 200 vessels sailed from Alexandria to Syracuse, the ancient capital of the island, which was besieged and then violently plundered. After this disastrous attack, the city's mighty walls were heavily damaged, and there were no more funds available to restore them. As a result, it was decided to fortify only the citadel.

This slow process of military and defensive disintegration led to a weakening of the island, although this was mitigated slightly by the arrival of the administrative reform of the themata. Sicily became 'Sikelia thema'. The strategos served as the military and political leader of the island and resided in Syracuse. He commanded two turmai, composed of about 1000 men each. A turma was in turn composed of several bands, following the typical subdivision described by the Mauritian Strategikon. The Sicilian theme also had a fleet called stolus siciliensis, which was capable of moving with good speed against enemy ships.

After the fall of Ravenna in 751, only a large part of what is now Calabria, Puglia, and the whole of Sicily remained under Byzantine rule. For this reason, the island was militarily strengthened, using the few