No contemporary account of Trajan's Parthian War survives, nor were any monuments set up to commemorate his exploits in the East in the same way that Trajan's Column in Rome and the trophy at Tropaeum Traiani (Adamclisi) do his Dacian Wars. We rely almost entirely on the excerpts of Dio Cassius' History preserved by Xiphilinus, together with a few fragments of Arrian's Parthica, in order to reconstruct the causes, objectives and strategy of the war. Because of the scant nature of the sources, all three aspects remain the subject of much scholarly discussion and dispute. Here, however, an attempt is made to address the problems raised by Trajan's eastern campaigns from a different perspective. References in fourth-century sources shed light not only on the purpose and execution of the war itself, but also on the way Trajan was perceived in late antiquity as a valuable paradigm for contemporary events and figures.

6 So Mitford, op. cit. (n. 4), 1196 n. 65. Those members of the Eastern Frontier of the Roman Empire Colloquium, held in Ankara in September 1988, who participated in the subsequent tour could, I am sure, vouch for the mountainous nature of the terrain. For this route, see French, D. H., ‘New research on the Euphrates frontier: Supplementary notes 1 and 2’, in Mitchell, S. (Ed.), Armies and frontiers in Roman and Byzantine Anatolia (1983), 84–6, fig. 7. 1.

9 The only comparable evidence on which I have been able to draw is that for Julian's expedition. He covered the journey from Antioch to Hierapolis, a distance of some 220 km, in five days. This indicates to me that he was riding poste-haste along good roads to meet the army, which had already mustered at Hierapolis, rather than that he was marching ‘with a force of some eighty to ninety thousand men’ (Bowersock, G. W., Julian the Apostate (1978), 108). From Hierapolis Julian's progress slowed considerably and he only reached Callinicum (after a detour to Carrhae) on 27 March. This makes a round trip of about 225 km in 16 days, or 14 km per day. It is from this last figure that I have derived my rough estimate of 15 km or just over 9 miles per day for Trajan's rate of march. Since the army had to negotiate formidable mountain ranges in order to reach Satala, I have deliberately made this slower than Casson's private traveller, whom he expected to do about 15 to 20 miles a day on foot ‘in normal terrain, with no toilsome slopes to negotiate’ (Casson, L., Travel in the ancient world (1974), 189).

20 See Angeli Bertinelli, op. cit. (n. 5), 14–15. The location of Adenystrae is most uncertain. Dillemann (op. cit. (n. 13), 285) rejected an earlier identification of the site with Dunaisir, south-west of Mardin, and instead equated it with Ad Herculem, which Sir Aurel Stein placed at Jaddalah. However, recent excavations of the site at Jaddalah have cast serious doubt on this identification; see Gregory, S. and Kennedy, D., Sir Aurel Stein's limes report (1985), 399. Toynbee, J. M. C., ‘Some problems of Romano-Parthian sculpture at Hatra’, JRSLXII (1972), 106–7 and pl. 5/1–2; see also Chaumont, M.-L., ‘A propos de la chute de Hatra’, Acta Antiqua Academiae Scientarium Hungaricae27 (1979), 227 f. —an article which I have been unable to consult in Ankara.

21 Dio LXVIII 26. 1; see Taylor, J. G., ‘Travels in Kurdistan, with notices of the sources of the eastern and western Tigris, and ancient ruins in their neighbourhood’, Journ. Royal Geographical Soc.35 (1865), 56.

22 This episode has for long struck me as strange, since I find it impossible to believe that the Jaghjagha (Çaçak Dere) was navigable in antiquity. The idea that a fleet was constructed at Nisibis in order for it to sail down to the Euphrates is quite fanciful.

29 For the arch, see Gould, op. cit. (n. 25), 56—65. Fragments of Arrian's Parthica name other sites along the Euphrates which may mark stages in the advance of Trajan's army in A.D. I 16 (Phalga fr. 8, Naarda fr. 10, and Anatha fr. 64 Roos).

46 L. Catilius Severus, consul in a.d. 110 and 120 (ILS 1041). Another inscription (ILS 1338), which mentions the post of procurator Augusti Armeniae Maioris, is attributed to T. Haterius Nepos and dated to the same period. For other evidence for the Roman establishment in Armenia, see Chaumont, op. cit. (n. 35), 138–9; J. Crow, ‘A review of the physical remains of the frontier of Cappadocia’, in Freeman and Kennedy, op. cit. (n. 32), 80–1, with CIL III. 13627a.

53 For Trajan's pre-eminence in fourth-century eyes and his equation with Theodosius, see Syme, R., Emperors and biography. Studies in the Historia Augusta (1971), 91–4, 101–3, and 110–11.

54 See, most recently, Barnes, T. D., ‘Constantine and the Christians of Persia’, JRSLXXV (1985), 130–2. Barnes draws attention to the fact that in his campaigns north of the Danube Constantine ‘was comporting himself like a new Trajan’.