 These would form, with the exception of Cythera, the Byzantine theme of Cephallenia in the late 8th century.From the late 11th century, the Ionian Islands became a battleground in the Byzantine–Norman Wars.The island of Corfu was held by the Normans in 1081–1085 and 1147–1149, while the Venetians unsuccessfully besieged it in 1122–1123.