During the Roman–Sasanian War of 421–422, the magister militum per Orientem, Ardaburius, invaded and plundered Arzanene in 421. Ardaburius engaged and defeated the Sasanian grand vizier, Mihr Narseh, and with reinforcements besieged Nisibis. The army of Al-Mundhir I, an ally of the Sasanians, who had been sent to relieve Nisibis, was defeated by Ardaburius beneath the walls and dispersed.[11] Ardaburius' victory over Al-Mundhir I led the new Shah, Bahram V, to end his siege of Theodosiopolis and march to relieve Nisibis, causing the Romans to abandon the siege.[12]