However, after the emperor Julian was slain during his failed campaign in Persia in 363, Rome ceded control of Iberia to Persia, and King Varaz-Bakur I (Asphagur) (363-365) became a Persian vassal, an outcome confirmed by the Peace of Acilisene in 387 However, a later ruler of Kartli, Pharsman IV (406-409), preserved his country's autonomy and ceased to pay tribute to Persia. Persia prevailed, and Sassanian kings began to appoint a viceroy (pitiaxae/bidaxae) to keep watch on their vassal. They eventually made the office hereditary in the ruling house of Lower Kartli, thus inaugurating the Kartli pitiaxate, which brought an extensive territory under its control.