This book provides a synthesis of modern research on the relationship between Roman emperors and their armies, up to the end of the Severan dynasty, suitable for a wide audience. It derives from the author’s PhD dissertation, undertaken under the supervision of Brian Campbell, who authored the definitive work on the same theme and whose intellectual fingerprints are evident in Eaton’s conceptual and methodological approach. Consequently, specialists will not find much that is new here; but they do not seem the primary target. The book’s merits lie primarily in its promotion to a more general reader of a Roman army firmly embedded within its wider socio-political contexts, although non-Romanists may feel the absence of much indication of chronology. For the reader who already possesses some familiarity with the period in question, the book provides an enjoyable and easy read, with its thematic approach clearly expounding Eaton’s central thesis that emperors were generally able to maintain a tight hold on the leash of their fearsome armies through a remarkably successful system of checks and balances. This argument is advanced through six thematic chapters that broadly work themselves outwards from Rome, and up the military hierarchy, taking the reader through the political role of the Rome garrisons, the centrality of discipline and morale to the soldier, the legionary centurionate, the military roles of equestrians and senators, political awareness within the various levels of the military, and the emperors’ self-representation to their armies.
Eaton covers the same period as Campbell, with the chronological boundaries set at Actium in 31 BC and the end of the Severan dynasty in AD 235. The terminal date also recalls the starting point for Hebblewhite’s 2017 monograph, which reads very much like a continuation of Campbell 1984, on emperors and armies in later Roman history. Although the chronological scope and thematic approach feel familiar and help position Eaton’s work as a spiritual successor to Campbell (and thus also a prequel to Hebblewhite), it is curious that the selected terminal date receives no justification here. One of Eaton’s stated goals is to counter such accounts of the relationship between emperors and armies as that offered in Birley 2007—which sneaks into the years that followed the Severans—broadly driven by narratives of “the rare occasions that the system broke down rather than the normal circumstances under which it worked” (ix). The consequence of Eaton’s approach is that we are left with the impression of an army whose relationship with the emperors during the period in question was, following the experiments of the early Julio-Claudians, broadly static and largely fruitful for both parties, implying a sudden and dramatic watershed around 235. This reviewer therefore believes that the book would have benefited from consideration of any longer-term shifts in the relationship between armies and emperors that precipitated the rapid turnover of emperors following the end of the Severan dynasty.
The chapters themselves are clearly organised and, with one exception, well-balanced in length. Eaton begins with the units stationed at Rome and their contradictory position, simultaneously providing protection but threatening danger to the emperors. Amongst other tools used to maintain control over the garrisons, Eaton suggests that intra-garrison unit rivalry helped prevent units collectivising to launch a coup. But rivalry between units risks fragmentations into distinct groupings, and the second chapter presents the importance of virtus and the emperor’s role as commilito in maintaining a united identity across the legions despite their distinct geographic areas of operation. Eaton further argues here that by effectively making the army commanders responsible for military discipline, emperors could appear simultaneously in control of the army while not falling out of favour with the soldiery. The third chapter, on “The Legionary Centurionate”, is by some way the shortest and, for this reviewer, also the weakest. Most of the material here is a cursory conspectus of the centurionate, sailing through the usual suspects in brisk order. More original is a review of centurions on the battlefield, which offers the intriguing hypothesis that they took up their combat/command positions in the second—and not the first—rank (46-7). The most interesting sentence within this chapter comes during the very short section on centurions’ relationships with army commanders, and notes “clear evidence of the targeted movement of centurions [by emperors] during times of political unrest” (49). This goes on simply to refer the reader to the author’s own 2017 paper on “The political role of the legionary centurions”. This point is restated in the conclusion to this chapter (129), and is clearly considered one of the key features of the centurionate by the author. So it is frustrating that the primary evidence for such an important interpretation is not discussed at greater length here. Given the brevity of this chapter, this reviewer believes that dividing its content amongst the other chapters and expanding upon its original ideas would have better served the book. Chapters 4-6, which are all longer than the first three, contain the real meat of the book. Chapter four emphasizes that generals very rarely proved overtly disloyal, and that the key attribute for a military commander in the period covered was loyalty to the emperor. Chapter five argues for the importance of coinage and statuary in enabling emperors to overcome their normal physical absence from the lives of their soldiers. It also posits that soldiers were attracted to imperial candidates who could provide a dynasty and stability—they were not mere bandits. Chapter six builds upon the rest of the book to provide a compelling account of the centrality of military support to the success of any emperor.
Eaton’s arguments are supported by a range of material throughout the book. Literary sources predominate, but these are often complemented by documentary materials from the epigraphic and papyrological records. There is some engagement with material culture, though the use of artistic representations is mostly confined to the interesting discussion on the use of severed heads as trophies (121-6). The book is well-served by the deployment of numismatic evidence to illustrate the ways in which emperors sought to present, to both military and non-military audiences, their mutually beneficial relationship with their armies. It is unfortunate that these discussions are not supplemented by relevant images of the objects discussed. Indeed, the photographs selected for inclusion (between pages 82 and 83), though of high quality, are generic and somewhat disappointing (e.g. the Colosseum, Hadrian’s Wall, the ara pacis). Nowhere does the text reference the photographs, and one suspects that they are an addition by the publishers. Pairing the discussion of specific scenes from the columns of Trajan and Marcus Aurelius (117: on the emperor awarding decorations; 121-6: on severed heads as trophies) with photographs of these scenes would have been more beneficial than the stock photographs of the columns that are provided. And how much more useful the photographs could have been if they had been used, say, to present images of the coin issues discussed on pages 12 and 83-89.
The book is not always up to date on academic debates. For instance, discussion of the emperor’s role in providing benefits for the military cites the so-called “marriage ban” on serving soldiers, and the role of Septimius Severus in rescinding it (108); reference is made to Phang 2001, but no awareness is indicated of Eck’s 2011 challenge, based upon the military diplomas, to the assumption that it was Severus who permitted soldiers to conduct legal marriage. Whether or not Eck’s arguments are accepted, their consequences for Eaton’s account of imperial beneficence towards soldiers at least merit attention. Elsewhere existing debates and alternative viewpoints are not always acknowledged. For example, the statement in the appendix on units at Rome, that trecenarius refers to someone who had held the trio of centurionates in the vigiles, urban cohorts and Praetorian Guard (134), follows the hypothesis in Mann 1983 without recognition of competing explanations for this obscure term.
An appendix provides a short overview of the military units based at Rome (and their increasing size) during the period in question, giving a sense of the origins of, and promotion and transfer patterns for, the soldiers within these units. There are forty-one pages of endnotes which consist primarily of references to scholarship and primary sources; more discursive notes offering further interrogation of material cited in the main work are on occasion also present. The bibliography is nineteen pages, although this is decidedly geared towards the Anglophone sphere, with just six percent in languages other than English. The index is rather short, and mostly consists of names (including, curiously, Ronald Syme as a sole representative from secondary scholarship amongst the host of ancient names).
The text has been well proof-read and is virtually without errors of fact or spelling. Some typographical errors do occur in the Abbreviations, and Fink’s 1971 work is properly Roman Military Records on Papyrus (hence RMR), not Roman Military Documents on Papyrus as recorded here (139). Confusingly, the index amalgamates under “Calpurnius Piso”, with no differentiation, references to three distinct individuals: Cn. Calpurnius Piso (d. AD 20), subject of the senatus consultum de Cn. Pisone patre; C. Calpurnius Piso (d. AD 65), conspirator against Nero; and the Tiberian urban prefect L. Calpurnius Piso Caesonius (d. AD 32). Cn. Piso and the senatorial decree against him receive significant and repeated attention; but C. Piso and the so-called “Pisonian conspiracy” are blink-and-you-miss-it (107 and 123). And yet the lack of distinction between the Pisones within both the index and the text risks leading the non-specialist into confusion. Similarly, following up references in the index to Quinctilius Varus, we find that pages 41-2 concern instead the very different Arrius Varus.
There is a question of readership. For specialists working on the Roman army this book will feel too general, and offer too little engagement with current academic debates; for non-Romanists, the lack of a clear indication of chronology, and the frequent dropping of names or mention of events with minimal context, may demand additional research from the reader. Students and others already familiar with the chronology and themes of the historical period in question may derive interest from this new accounting of the mechanisms that underpinned the subordination to the emperors of the armies of Rome; but it should be read as an update to, rather than a replacement of, Campbell’s 1984 monograph on the same topic—still the gold standard. Nonetheless, Roman army enthusiasts in particular will find themselves right at home with this book, and for this audience Pen and Sword have enabled an enjoyable and useful addition to their catalogue.
 Campbell, J.B. (1984). The Emperor and the Roman army 31 BC – AD 235.
 Hebblewhite, M. (2017). The emperor and the army in the later Roman empire, AD 235-395.
 Birley, A.R. (2007). “Making Emperors. Imperial Instrument or Independent Force?” In P. Erdkamp (ed.) A Companion to the Roman Army.
 In Parker, A. Ad Vallum: Papers on the Roman Army and Frontiers in Celebration of Dr Brian Dobson. BAR British Series 631.
 Phang, S. (2001). The Marriage of Roman Soldiers (13 B.C.-A.D. 235): Law and Family in the Imperial Army.
 Eck, W. (2011). “Septimius Severus und die Soldaten: das Problem der Soldatenehe und ein neues Auxiliardiplom”. In Onken, B. & Rohde, D., (eds). In omni historia curiosus: Studien zur Geschichte von der Antike bis zur Neuzeit: Festschrift für Helmuth Schneider zum 65. Geburtstag.
 Mann, J.C. (1983). “Trecenarius”, Zeitschrift für Papyrologie und Epigraphik, 52. But contrast alternative interpretations at e.g. Domaszewski, A.von. (1908). Die Rangordnung des römischen Heeres, p.99; Dobson, B. and Breeze, D.J. (1969). “The Rome cohorts and the legionary centurionate”, Epigraphische Studien, 8, pp.118-119; Summerly, J.R. (1992). Studies in the Legionary Centurionate, Durham PhD Dissertation, p.9.