the city of Nisibis had been handed over to the Persians as one of the conditions of the peace which closed the unfortunate war commenced by Julian, and the members of the school, retiring into Christian territory, had re-assembled at Edessa, where a school was opened in 373, and thus Edessa in a Syriac speaking district but within the Byzantine Empire, became the centre of the vernacular speaking Syriac church.
At the Nestorian schism the school at Edessa was the rallying place of those who did not accept the decisions of Ephesus, but in 439 it was closed by the Emperor Zeno on account of its strong Nestorian character, and the ejected members led by Barsuma, a pupil of Ibas (d. 457), who had been the great luminary of Edessa, migrated across the Persian border. Barsuma was able to persuade the Persian king Piruz that the orthodox, that is to say the state, Church was pro-Greek, but that the Nestorians were entirely alienated from the Byzantine Empire by the harsh treatment they had received. On this understanding they were favourably received and remained loyal to the Persian monarchy in the subsequent wars with the Empire. The Nestorians re-opened the school at Nisibis and this became the focus of Nestorian activity by which an orientalised phase of Christianity was produced. Gradually the Nestorian missionaries spread through all central Asia and down into Arabia so that the races outside the Greek Empire came to know Christianity first in a Nestorian
