Severus Alexander advanced towards Ctesiphon in 233, but as corroborated by Herodian, his armies suffered a humiliating defeat against Ardashir I. In 283, emperor Carus sacked the city uncontested during a period of civil upheaval. In 295, emperor Galerius was defeated outside the city. However, he returned a year later with a vengeance and won a victory which ended in the fifth and final capture of the city by the Romans in 299. He returned it to the Persian king Narses in exchange for Armenia and western Mesopotamia. In c. 325 and again in 410, the city, or the Greek colony directly across the river, was the site of church councils for the Church of the East.