Following the death of his father in 337, Constantine II became emperor jointly with his brothers Constantius II and Constans. After the division of the empire, made by the three brothers in September of the same year in Pannonia, he ruled over Gaul, Britannia and Hispania. He was involved in the struggle between the different Christian streams. The Western portion of the empire leaned towards Catholicism and against Arianism, and Constantine freed Athanasius and allowed him to return to Alexandria. This action also put some burden on Constantius II, who was a supporter of Arianism.