This is a generous and important book. Johannes Wienand has brought together eighteen papers by as many contributors and fashioned them into an elegant study in three parts of six papers each: (i) ‘Administering the Empire’ (15–148); (ii) ‘Performing the Monarchy’ (149–288); (iii) ‘Balancing Religious Change’ (289–419). His epilogue, though somewhat laboriously called ‘The Empire's Golden Shade: Icons of Sovereignty in an Age of Transition’ (421–51), is a substantive paper in its own right, concerning imperial gold medallions.

Despite something of a star cast, there has been no egregious resting on laurels. Every paper deserves to be read individually. But to read the book as a whole raises questions that will remain basic for some years to come.

To begin with: whence and whither ‘contested’ monarchy?

The main title is borne out by usurpation, and by competing notions of monarchy. But at times, the subtitle bears greater weight: even when monarchy was not directly contested, imperial integration could not be taken for granted. Doug Lee (‘Emperors and generals in the fourth century’, 100–18) underlines that it was ‘essential for emperors to devise strategies for discouraging ambitious generals from contemplating disloyalty’ (101). Of the execution of the magister Barbatio and his wife, Lee remarks: ‘perhaps most interesting about the whole episode is that a figure such as Barbatio should have considered himself a potential emperor, when the Constantinian dynasty was still in place after many decades' (115). Even if Barbatio was hard done by, Constantius II's insecurity is revealing. One is reminded of the widely misattributed aphorism of Delmore Schwartz: ‘Even paranoids have real enemies.’ Magnentius' usurpation was no reassurance. It is perhaps no wonder that Valentinian and Valens sought quickly to put down roots in a bout of ‘ostentatious’ law-making — as Sebastian Schmidt-Hofner aptly calls it in his important and meticulous contribution (‘Ostentatious legislation: law and dynastic change, AD 364–365’, 67–99).

To put this another way, for ‘contested’ monarchy we should in part understand an ever-present sense that monarchy might be fought over, and hence that it needed constant shoring up. This was not merely the obsession of watchful rulers and the twitchier members of their entourage. John Noël Dillon (‘The inflation of rank and privilege: regulating precedence in the fourth century AD’, 42–66) and Michael Kulikowski (‘Regional dynasties and imperial court’, 135–48) highlight the intersections between provincial aristocratic and courtly concerns, and the rôle of imperial service in that juncture. John Weisweiler (‘Domesticating the senatorial elite: universal monarchy and transregional aristocracy in the fourth century AD’, 17–41) underlines that the senate turned ‘from an ostensibly Republican elite into a proudly monarchical aristocracy’ (35). The senators had good cause: from the 360s they were mostly enrolled in recognition of their imperial service.

This shoring up did not always work. Joachim Szidat (‘Gaul and the Roman emperors of the fourth century’, 119–34) emphasizes the idiosyncrasy of the Gallic experience — a nursery of usurpation. Szidat's convenient list of claimants between the 290s and 390s has ten individuals, seven from 350 onwards (134). We can take Decentius in tandem with his brother Magnentius (127). But this still looks like a systemic problem — not the least outcome of which was, perhaps, a haemorrhaging of the West's ability to confront external pressures. It may be symptomatic that, as Henning Börm points out (‘Born to be emperor: the principle of succession and the Roman monarchy’, 239–64), the focus of contestation would gravitate in the fifth century to the position of magister militum (263).

So in turn: by what symbolic or rhetorical means did the many ‘stakeholders’ in the integration of empire invest in an ever-precarious monarchy?

Successive imperial courts knew how to live down their failures. Wienand himself focuses (‘O tandem felix civili, Roma, victoria! Civil-war triumphs from Honorius to Constantine and back’, 169–97) on the peculiar prevalence of civil-war triumphs and their accompaniment by ‘elements of conspicuous brutality’ (176). But read in light of Hartmut Leppin's paper (‘Coping with the tyrant's faction: civil-war amnesties and Christian discourses in the fourth century AD’, 198–214), this demonstrative violence looks like an escape valve. Leppin emphasizes that emperors ‘could never afford bloody reprisals that would demand many victims’ (214). Amnesty was instead the main fate of supporters. When Mark Humphries points out (‘Emperors, usurpers, and the city of Rome: performing power from Diocletian to Theodosius', 151–68) that the usurpations of Maxentius, Magnentius and Magnus Maximus provide ‘a context for understanding the subsequent imperial visits' to Rome (161), one senses that bridge-building mattered.

We are also dealing with an ambiguous Constantinian legacy. Christian Reitzenstein-Ronning (‘Performing justice: the penal code of Constantine the Great’, 265–88) notes both an ideological and a practical dimension in the punishments laid down by Constantine: on close inspection, much legislative severity was rhetorical and ‘restricted to some well-defined areas' (288). Bruno Bleckmann (‘Constantine, Rome, and the Christians’, 309–29) explores the relation between Constantine's capture of Rome and his self-representation, wrestling not least with the emperor's church-building on the city periphery. Noel Lenski (‘Constantine and the Tyche of Constantinople’, 330–52) identifies neutral rituals by which Constantine ‘founded a new cult in his new city that was anything but strictly Christian’ (351).

How this legacy was modified is most obviously shown in the Christian sphere. Steffen Diefenbach (‘A vain quest for unity: creeds and political [dis]integration in the reign of Constantius II’, 353–78) argues that Constantius II was a good deal less bothered by credal formulae than often supposed. He was, however, quite ruthlessly disposed to rid himself of turbulent priests. Yet the use of violence could spiral away from emperors. In sometimes sharply negative language, Johannes Hahn points out (‘The challenge of religious violence: imperial ideology and policy in the fourth century’, 379–404) that ‘Christian religious violence eroded the monopoly of the late-antique state on the legitimate use of force’ (398). And Rita Lizzi Testa (‘The famous “Altar of Victory controversy” in Rome: the impact of Christianity at the end of the fourth century’, 405–19) offers a close reading of an old chestnut, vindicating a réaction païenne — and hence the survival of public paganism. But she does so in such modified, downbeat terms that one thinks of what a modern dramatist might call a ‘political procedural’.

Yet we are also looking at a strange and compelling mobilization of ancient modes of thought. Christopher Kelly (‘Pliny and Pacatus: past and present in imperial panegyric’, 215–38) reminds us that manuscripts of the XII Panegyrici latini have Pacatus immediately after Pliny. Reading them side by side, Kelly finds a ‘network of correspondences between the two’ (236). To an extent we had not appreciated, Pacatus spoke, in a.d. 389, in defence of a deep tradition of idealized monarchy. Conversely, as Harold Drake highlights (‘Speaking of power: Christian redefinition of the imperial role in the fourth century’, 291–308), Eusebius, Chrysostom and others re-inflected classical thought, to varying degrees, on pugnacious Christian lines — contesting the rôle of emperors ‘over access to the divine’ (307).

This is a book that deepens our sense of the complexity, and unexpectedness, of the late Roman Empire. It is a landmark.