Notwithstanding the fact that the peace agreement between Rome and Persia was generally observed, the Euphrates frontier and Armenia remained regions of continual tension, aggravated by the fact that they had become religious frontiers as well. Yezdegird I (399–420) initially pursued a policy of religious toleration within the Persian Empire, issuing a decree in 409 that permitted the Christians to rebuild their churches and to practice their religion openly. It also established what later became known under the Turks as the millet system, whereby the Christians and other subject religious communities were accorded a special status that permitted them to deal with the Persian authorities through a communal leader that was formally appointed for the purpose by the government. However, Yezdegird’s policy of religious toleration soon began to create internal problems for him with the official Persian religious establishment. Under considerable domestic pressure, the king made a dramatic reversal of policy that triggered an intense persecution of the Christians during the last five years of his reign.
The persecutions were continued by his successor Bahram V (420–439), and became so intense that a large number of Christians fled across the frontier to seek Roman protection. Bahram demanded of Theodosius II (408–450) that these Persian subjects be deported back to Persian territory. When the Byzantine (Roman) emperor refused to turn over the refugees, Bahram prepared for war. Anticipating that this would happen, the Byzantines took to the field before the Persians were fully ready for hostilities. The Byzantine commander, Ardaburius, marched his army through Armenia into the Persian province of Arzanene where he defeated the troops sent by Bahram to block his passage, and proceeded to plunder the area. But the