 Another reason was due to Constantine, who at his deathbed in 337, had declared Christianity as the official religion of the Roman Empire.He had also selected himself as the defender of all the Christians in the world, including those living in the Sasanian realm.In 337, just before the death of Constantine the Great (324–337), Shapur II, provoked by the Roman rulers' backing of Roman Armenia, broke the peace concluded in 297 between emperors Narseh (293–302) and Diocletian (284–305), which had been observed for forty years.