In approximately 120 BC, the Parthian king Mithridates II () invaded Armenia and made its king Artavasdes I acknowledge Parthian suzerainty. Artavasdes I was forced to give the Parthians Tigranes, who was either his son or nephew, as a hostage. Tigranes lived in the Parthian court at Ctesiphon, where he was schooled in Parthian culture. Tigranes remained a hostage at the Parthian court until , when Mithridates II released him and appointed him as the king of Armenia. Tigranes ceded an area called "seventy valleys" in the Caspiane to Mithridates II, either as a pledge or because Mithridates II demanded it. Tigranes' daughter Ariazate had also married a son of Mithridates II, which has been suggested by the modern historian Edward Dąbrowa to have taken place shortly before he ascended the Armenian throne as a guarantee of his loyalty. Tigranes would remain a Parthian vassal until the end of the 80's BC.