Antiochus III launched a massive campaign to retake Parthia and Bactria in 210 or 209 BC. Despite some victories he was unsuccessful, but did negotiate a peace settlement with Arsaces II. The latter was granted the title of king (Greek: "basileus") in return for his submission to Antiochus III as his superior. The Seleucids were unable to further intervene in Parthian affairs following increasing encroachment by the Roman Republic and the Seleucid defeat at Magnesia in 190 BC. Priapatius ("r". c. 191–176 BC) succeeded Arsaces II, and Phraates I ("r". c. 176–171 BC) eventually ascended the Parthian throne. Phraates I ruled Parthia without further Seleucid interference.