Contrary to his predecessor Artaxerxes IV Arses, Darius was a distant member of the Achaemenid dynasty. During his early career, he was reportedly an obscure figure among his peers and first rose to prominence during the Cadusian expedition of Artaxerxes III in the 350s BC. As a reward for his bravery, he was given the Satrapy of Armenia. Around 340 BC, he was made in charge of the royal "postal service," a high-ranking position. In 338 BC, Artaxerxes III met an abrupt end after being poisoned by the court eunuch and chiliarch ("hazahrapatish") Bagoas, who installed his youngest son Arses on the throne. He only reigned for a few years, until Bagoas had him poisoned as well. Darius was subsequently installed on the throne and soon forced Bagoas to drink his poison after discovering that the eunuch had planned to poison him as well.