According to one version, he succeeded his father Khosrov III in 338, placed on the throne by the Roman emperor Constantius II after a Persian invasion of Armenia.
During the course of the Sasanian king Shapur II's campaigns against the Roman Empire in the 340s, Tiran was reportedly betrayed by one of his vassals, captured by the Persians, and blinded.
[12] Suren Yeremian suggests that Tiran sought to free himself from the tutelage of the clergy and adopt a more lenient attitude towards his non-Christian subjects, thus winning over the anti-Roman and anti-Church section of the nobility.
[14] After this, the prominent chorbishop Daniel was also murdered on Tiran's orders,[15] and the leadership of the Armenian church passed, for a time, from the Gregorids to the patriarchs of the line of Albianos, who were obedient to the king.
[13] The Buzandaran Patmutʻiwnkʻ also records Tiran's conflict with the Armenian nobility, incited by the eunuch official Hayr Mardpet.
[16] In Yeremian's view, Tiran, with the help of Hayr Mardpet, centralized royal authority, punished the Armenian magnates with "separatist aspirations" and seized their holdings; this turned the nobility, especially its pro-Roman wing, against him.
[13] During Tiran's reign, the Sasanian king Shapur II launched several campaigns against Rome, during which Armenia was devastated by the Persians.
[17] Both Khorenatsi and the older Buzandaran Patmutʻiwnkʻ report that Tiran was captured and blinded by the Persians, after which he was succeeded by his son Arshak II.
At this point, writes Yeremian, Tiran changed his policy and reconciled with the pro-Roman party, provoking Shapur's wrath.
However, after the Battle of Singara and the death of the Persian prince Narseh, he was allowed to return to Armenia in 345 to be succeeded by his son Arshak II.