It is the purpose of this paper to examine how Ammianus, Libanius, and Julian conceived of Roman policy on the eastern frontier from the death of Constantine to failure of Julian′s invasion of Persia. Any consideration of the actual facts is secondary. The predominant conclusion will be that all three saw Rome′s as essentially defensive, her objective as the containment of persistent aggression. This will be seen to hold good even for Julian′s invasion., when they are offered by the sources, are presented in terms of, whether national or that of individuals: Constantius, Julian, Jovian, and. It will become apparent, and is sometimes implied, that these attitudes derive the peace imposed by Rome in 299, with which Rome could well rest content, Persia clearly could not.