The Seleucids had suffered heavy defeats by the Iranian Parthian Empire; in 148/7 BC, the Parthian king Mithridates I () conquered Media and Atropatene, and by 141 BC, was in the possession of Babylonia. The menace and proximity of the Parthians caused Hyspaosines to declare independence. In 124 BC, however, Hyspaosines accepted Parthian suzerainty, and continued to rule Characene as a vassal. Characene would generally remain a semi-autonomous kingdom under Parthian suzerainty till its fall. The realm of the kingdom included the islands Failaka and Bahrain.