He first became prominent during a campaign in 1031, when the Byzantines were defeated at Aleppo but went on to capture Edessa from the Seljuk Turks. His greatest achievement was the partial reconquest of Sicily from the Arabs beginning in 1037. Here, he was assisted by the Varangian Guard, which was at that time led by Harald Hardrada, who later became king of Norway. There were also Norman mercenaries with him; although the Arabs soon took the island back, Maniaces' successes there later inspired other Normans to invade Sicily themselves.
Maniaces' accomplishments in Sicily were largely ignored by the Empire, and he revolted against Constantine IX in 1042. Maniaces was proclaimed emperor by his troops (including the Varangians), and marched towards Constantinople, but he was killed in 1043 when troops loyal to Constantine met him near Thessalonika.
