In his Life of Constantine (Vita Constantini 4.8–14), Eusebius presents what he claims is a translation of a letter that Constantine sent to the Persian Emperor Shapur II. In the letter, Constantine remarks on how delighted he is to hear that there are many Christians in Persia, how Christ and the Christian religion had helped him in his reign, and how earlier pagan emperors of Rome had suffered ills (including Valerian, who Shapur's grandfather had defeated and taken prisoner). Constantine concludes the letter by commending the Christians of Persia to the care of Shapur. Many modern scholars, including T. D. Barnes (“Constantine and the Christians of Persia,” Journal of Roman Studies 75 [1985]: 126–136), have accepted a narrative in which this letter plays a central role in motivating Shapur to launch a persecution against Christians in Persia because he viewed them as pro-Roman. In this new book, Kyle Smith of the University of Toronto challenges the standard narrative that Constantine was planning an invasion of Persia to liberate Christians and that Shapur persecuted Persian Christians because he perceived them as fifth columnists loyal to Rome. Throughout the book, Smith makes effective use of Syriac sources (many of which have not previously been translated into English or used in depth by Western scholars).

Smith sets the book up in two major parts: “The Roman Frontier and the Persian War” and “Roman Captives and Persian Envoys.” He points out, as some other scholars have noticed (Miriam Raub Vivian, “A Letter to Shapur: The Effect of Constantine's Conversion on Roman-Persian Relations” [PhD diss., University of California–Santa Barbara, 1987]), that Constantine's letter in and of itself does not necessarily show tension between Constantine and Shapur (and that commending the Christians to Shapur's care seems to suggest he is being viewed as a legitimate ruler). Smith suggests a dating range of 324/325 for Constantine's letter, but does allow that Constantine was preparing a military expedition against Shapur in 336/337 (more as part of the continuing struggle over the Eastern frontier than due to religious reasons). This struggle would explode into open warfare between Shapur and Constantius II after Constantine's death (and that long conflict may also have shaded the lens through which scholars view Roman-Persian relations under Constantine). Unfortunately, there is a lacuna in the text of Eusebius's Life of Constantine at 4.57 where more about the cause of the conflict in the last months of Constantine's life might have been revealed.

Smith shows that most of our knowledge of Shapur's persecution comes from later Syriac sources. Following the kind of approach used by Raymond van Dam to unravel the history of the story of Constantine's victory at the Milvian Bridge (Remembering Constantine at the Milvian Bridge [Cambridge University Press, 2011]), Smith argues that we have very little contemporary evidence of early fourth-century persecution of Christians in Persia, and that later Syriac authors retrojected the persecution to the period when Constantine and Shapur were contemporaries.

In part 2, Smith then turns to a close examination of the Syriac texts (including Aphrahaṭ’s Demonstrations, The Martyrdom of Blessed Simeon bar Ṣabba‘e, and the History of Blessed Simeon bar Ṣabba‘e) to understand them as works in their own right. In nuanced analyses of the primary sources as well as the secondary scholarship, Smith delves into the depiction of Persian Christians in these texts as Roman captives, often either as prisoners of war or captives from captured territory (such as the captives of Beth Zabdai) during the period ranging from the reign of Constantius II to Jovian. Smith ultimately returns to Constantine by examining his portrayal in Syriac sources (but not appearing until the fifth century), and so attempts to show how myths of Constantine “were constructed and memorialized” (177). Smith concludes by stating “this book is not a revisionist history at all but rather a critique of positive historiography” (177) and so shows the problems of the earlier scholarly narrative, but does not offer a new view of what really did occur in the genesis of Constantine's war with Persia. Smith offers several appendices presenting translations of primary sources and also presents a bibliography of primary and secondary sources.

This book is stimulating and I learned much from it. It might be possible to plan an approach to the origins of the conflict by returning to the difficult episode of the “Lies of Metrodorus” described in an allusion by Ammianus (Res Gestae 25.4.23) and Cedrenus, touched on by Smith at pp. 51–52 (see B. H. Warmington, “Ammianus Marcellinus and the Lies of Metrodorus,” Classical Quarterly 31, no. 2 [1981]: 464–468). While a few other sources mention Metrodorus, only Ammianus and Cedrenus described him as the catalyst for the war with Persia. Ammianus would have been well-informed about the origins of the conflict (having served in the war himself under Constantius II and Julian). The recent edition of Cedrenus's work (Luigi Tartaglia, ed., Georgii Cedreni Historiarum Compendium [Bardi, 2016]) might help us see if that eleventh-century author used the lost part of Ammianus's work as a source (and Roger Scott, John Burke, and Paul Tuffin are preparing the first English translation of Cedrenus's work). Andrew Wilson (“Water-Mills at Amida: Ammianus Marcellinus 18.8.11,” Classical Quarterly 51, no. 1 [2001]: 231–236) has suggested that Cedrenus's description of Metrodorus introducing water mills and baths to India also stems from the lost books of Ammianus. If so, then perhaps the fuller account of Metrodorus's lies to Constantine might reveal the cause of the conflict that had been brewing since Valerian's defeat, and accelerated with Diocletian's absorption of Mesopotamia.