George of Antioch's prior knowledge of the Zirid administration, his connections with an Armenian official in Fatimid Egypt, and knowledge of Greek and Arabic led to his rise in the Norman administration. He rose to the title of "familiaris" of the court and by 1123 had risen to second in command in Christodulus' navy. In these years, he also served as a frequent envoy to the Fatimid court in Cairo. In a Norman attack on Mahdia that year, George captured the fortress of ad-Dimas, located on the coast of Tunisia, but the campaign resulted in a decisive Norman defeat at the hands of the Zirid emir, al-Hasan ibn Ali. In the following five years, George overshadowed Chrisotodulus and by 1127 had replaced him in the position of emir of Palermo. In that year, both emirs were present at Montescaglioso with Count Roger, but Christodulus seems to have died soon thereafter and George succeeded him.