In the 360s, Athanaric, son of Aoric and leader of the Thervingi, supported the usurper Procopius against the Eastern Roman Emperor Valens. In retaliation, Valens invaded the territories of Athanaric and defeated him, but was unable to achieve a decisive victory. Athanaric and Valens thereupon negotiated a peace treaty, favorable to the Thervingi, on a boat in the Danube river, as Athanaric refused to set his feet within the Roman Empire. Soon afterwards, Fritigern, a rival of Athanaric, converted to Arianism, gaining the favor of Valens. Athanaric and Fritigern thereafter fought a civil war in which Athanaric appears to have been victorious. Athanaric thereafter carried out a crackdown on Christianity in his realm.