These rebellions help explain Antiochus' subsequent aggressive policy toward his satrap Xerxes. By 212 BC, Antiochus III had invaded the domain of Xerxes and defeated him after laying siege to the city of Arsamosata.[4] Shortly afterwards Antiochus III arranged for Xerxes to marry his sister, Antiochis.[5] However, within the same year she arranged to have her new husband assassinated, thinking that her brother would then be able to take control of Sophene. Whether Xerxes still ruled Commagene by the time of his assassination is not known.