_full_alt_author_running_head (neem stramien B2 voor dit chapter en dubbelklik nul hierna en zet 2 auteursnamen neer op die plek met and): 0 _full_articletitle_deel (kopregel rechts, vul hierna in): From Caesar to Augustus: Julian against Constantius _full_article_language: en indien anders: engelse articletitle: 0 From Caesar to Augustus: Julian against Constantius 97 Chapter 4 From Caesar to Augustus: Julian against Constantius Bruno Bleckmann 1 Introduction In February 360 Julian, who had ruled as subordinate Caesar since 355, was ele­ vated to the rank of Augustus by elite troops in Paris. A year later, after the col­ lapse of his negotiations with Constantius II, he sought to increase his chances in the impending conflict by occupying Illyricum. In May 361 he arrived in Sir­ mium, before stopping for a long time in Naissus, where he prepared for civil war. When Constantius II died on the 3rd of November in Mopsukrenai, sole rulership of the Roman Empire fell to Julian without a fight as a result of the decision by the Eastern commanders not to choose a pretender of their own. The turbulent period through which Julian acted as illegitimate Augustus – because he had not been recognized by the senior emperor – lasted just under two years. Yet the period is doubtless of great importance for an assessment of Julian’s rule and personality. This is particularly true of his abundant propa­ gandistic activities, discussed in greater detail below. If one focuses not on Ju­ lian himself but instead places his elevation in the wider context of Roman history in the fourth century, it becomes clear that this is one of many similar episodes in the history of the system of co­emperorship of late antiquity. This system of co­emperorship, the most common form of imperial govern­ ment since the Tetrarchy, took on many diverse configurations of greater or lesser stability.1 At times we see the rule of a senior emperor with subordi­ nate rulers (Caesares) assigned to individual territories; at others a senior em­ peror alongside nominally co­ruling Augusti who have no territory of their own, or a tense coexistence between two co­rulers of equal rank (Constantine versus Licinius; Constantius II versus Constans; Arcadius versus Honorius); finally, we also find the necessarily temporary co­rulership of a legitimate em­ peror and a competing pretender (Magnentius versus Constantius II). These rulers, however hierarchically related, were connected through complex sys­ tems of interaction. This interaction includes relationships of a familial and 1 Cf. Pabst, Divisio regni; Bleckmann, “Scheitern des Mehrherrschaftssystems”; Szidat, Kaiser und Usurpator, p. 372. © Koninklijke Brill NV, Leiden, 2020 | doi:10.1163/9789004416314_005 98 Bleckmann dynastic nature (kinship and marriage between co­rulers) as well as diplomat­ ic relationships with contractual agreements and the demarcation of territo­ ries. Other aspects of the organization of the co­emperorships have their origin in the relationships between Roman magistrates (seniority, collegiality, and hierarchies of authority), and in elements of traditional Roman social relation­ ships like clientship (the position of the subordinate ruler in relation to the senior emperor who elevated him). Aspects of these different modes of rela­ tionships could be incorporated into public display, which might, for example, emphasize the primacy of the auctor imperii and demonstrate the subordinate ruler’s recognition of his colleague’s seniority or superior rank. Multiple as­ pects of the internal relationships are, by contrast, less clear, for example the networks of civil, military, and clerical elites who also shape the relationship between the emperors. To this system of interaction between co­rulers we can add a panoply of confrontational possibilities, ranging from the refusal to ac­ knowledge a consul in one portion of the Empire, through the merely tempo­ rary recognition or total rejection of pretenders (usurpers), all the way to open civil war. The history of the co­rulership of Constantius and Julian is one of many in­ stances of a non­functional imperial college; the relationship between the co­ rulers moves through a series of increasingly tense configurations in quick succession, and the nature of the interaction changes swiftly – a situation per­ haps comparable to the collapse of the imperial college after the death of Con­ stantius I in AD 306. In his elevation of Julian in 355, Constantius II had followed the model in­ troduced by the Tetrarchy, that subordinate rulers with the title of a Caesar should maintain the imperial presence in distant provinces. This model func­ tioned fairly well at the start but finally broke down despite multiple precau­ tions such as forging ties through marriage politics and exploiting or creating other types of familial relationship. After Julian, Caesares were only appointed in some exceptional cases and during periods of transition.2 The reason for the definitive failure of the model of a subordinate Caesar lies in the fact that Julian was by no means an exception in not accepting this position and instead striving for the rank of Augustus. In fact, his behaviour reflects a structural problem. The sources for the first half of the fourth century provide examples of the dissatisfaction of several Caesars with their subordi­ nation: this ranges from the political pressure which Galerius is said to have exercised on Diocletian, through to the ambitions of Constantius Gallus, who 2 E.g. the elevation of Valentinian III to Caesar by his cousin Theodosius II. Constans, the son of the Usurper Constantius III, was likewise Caesar for some time..