The Religious Legitimation of War in the Reign of Antoninus Pius* André Heller Introduction Antoninus Pius (138–161) reigned twenty-three years, which makes him the lon- gest ruling emperor between Augustus and Constantine the Great. Nowadays, he is almost entirely perceived as a lacklustre figure compared to his predeces- sors and successors, though generally credited as faithful administrator of the Empire, which rejoiced in an unprecedented period of peace and prosperity under his reign. While modern scholarship recognises stagnation or regres- sion in Antoninus’ government, the ancient sources extol his foreign policy via diplomacy which guaranteed the compliance of Rome’s enemies. However, territorial gains in Britain and Germany contradict the opinion of an inactive emperor; even more puzzling are the many war-related themes on Antoninus’ coins. A close examination of the written sources, the reverses of the coins and the distance slabs of the Antonine Wall unveils a complex, though unparal- leled system how the emperor combined his need for military glory with the emphasis on the concept of just war and the invocation of the protective func- tion of the gods for Rome’s prosperity and security. Historical Setting When Trajan died in 117, the Roman Empire had reached its largest territo- rial extent after the conquest of Dacia (101–6), Armenia (114), Northern Mesopotamia (115), and the annexation of the Nabatean Kingdom (106). However, his expansionist policy overstressed the Empire’s resources due to the huge casualties in the Dacian and Parthian wars. Trajan’s successor Hadrian immediately concluded peace with the Parthians, relinquishing the Eastern conquests, as he faced the outbreak of revolts in several regions.1 Hadrian’s non-expansionist attitude, manifest through the building of walls in Britain, Germany, and Africa proconsularis, did not find favour with the senators’ * I wish to thank Krzysztof Ulanowski for inviting me to the conference. 1 SHA Hadr. 5.1–4. © koninklijke brill nv, leiden, ���6 | doi ��.��63/97890043�4763_0�9 The Religious Legitimation Of War 359 majority, vividly displayed by Hadrian’s negative stance in the historiography which was influenced by his difficult relationship to the senate. Except for the troubled early years and the undoubtedly severe Bar Kokhba revolt (132–5), his reign was peaceful. On 25 February 138, Hadrian adopted the patrician T. Aurelius Antoninus, who succeeded him a few months later on 10 July. Antoninus’ cursus hono- rum only comprised civic functions—the proconsulship over Asia being the only post he had held outside Italy—and conformed to the typical career of a man of noble descent. It is likely that Hadrian chose him as he seemed a compliant continuator of his own defensive policies. Despite Antoninus’ long reign, there are only a handful of monographs on him, and accounts on the Roman imperial era dedicate just a few pages to him.2 This is certainly due to a remarkable lack of written testimonies3 which conveys the impression of an uneventful reign. As Cassius Dio’s Roman history is entirely lost for this period,4 the terse but reliable biography in the Historia Augusta is the main source.5 In his Roman Oration, delivered at Rome in 143,6 Aelius Aristides drew the most impressive picture of Antoninus’ reign and the peaceful state of the world, although the orator had to admit that wars did not entirely disappear, ‘as is only natural in the immensity of a great empire’.7 Likewise, the Historia Augusta or the emperor’s contemporaries Pausanias, author of a Description of Greece, and Polyaenus in his Stratagems, attest conflicts in remote regions of 2 Still valuable is the magisterial work of W. Hüttl, Antoninus Pius. 2 vols. (Prague: Calve, 1933–6); more recently, B. Rémy, Antonin le Pieux 138–161. Le siècle d’or de Rome (Paris: Fayard, 2005). 3 A.M. Kemezis, “Lucian, Fronto, and the Absence of Contemporary Historiography under the Antonines,” AJPh 131 (2010) 285–325. 4 K. Juntunen, “The Lost Books of Cassius Dio,” Chiron 43 (2013) 460–1; M.G. Schmidt, “Cassius Dio, Buch LXX. Bemerkungen zur Technik des Epitomators Ioannes Xiphilinos,” Chiron 19 (1989) 57–9. 5 Beside the Historia Augusta, there are the correspondence of Cornelius Fronto, Marcus Aurelius’ tutor, and the late-antique abbreviators Eutropius, Aurelius Victor, Festus, and the anonymous author of the Liber de Caesaribus. For a survey of the available sources, cf. S. Walentowski, Kommentar zur Vita Antoninus Pius der Historia Augusta (=Antiquitas IV/3,3; Bonn: Habelt, 1998) 61–88, and Rémy, Antonin le Pieux . ., 393–416. 6 R. Klein, “Zur Datierung der Romrede des Aelius Aristides,” Historia 30 (1981) 337–50, follow- ing J.H. Oliver, “The Ruling Power. A Study of the Roman Empire in the Second Century after Christ through the Roman Oration of Aelius Aristides,” TAPhS 43 (1953) 887, argued for 143 while C.A. Behr, Aelius Aristides and the Sacred Tales (Amsterdam: Hakkert, 1968) 88–90, and id. (trans.), Aelius Aristides. The Complete Works. Vol. II: Orations XVII–LIII (Leiden: Brill, 1981) 376–7 n. 77, pledged for 155. 7 Aristid. Or. 26.70 (trans. Oliver, “The Ruling Power . .)..