In 38 AD, Caligula reinstated Antiochus III's son Antiochus IV and also gave him the wild areas of Cilicia to govern. Antiochus IV was the only client king of Commagene under the Roman Empire. Deposed by Caligula and restored again upon Claudius' accession in 41, Antiochus reigned until 72, when Emperor Vespasian deposed the dynasty and definitively re-annexed the territory to Syria, acting on allegations "that Antiochus was about to revolt from the Romans... reported by the Governor Caesennius Paetus". The Legio VI Ferrata, which Paetus led into Commagene, was not resisted by the populace; a day-long battle with Antiochus' sons Epiphanes and Callinicus ended in a draw, and Antiochus surrendered. The Legio III Gallica would occupy the area by 73 AD. A 1st-century letter in Syriac by Mara Bar Serapion describes refugees fleeing the Romans across the Euphrates and bemoans the Romans' refusal to let the refugees return; this might describe the Roman takeover of either 18 or 72.