In this erudite and comprehensive study, Frederik J. Vervaet addresses the question of how the existence of formally equal magistrates could be brought into accordance with the necessity of maintaining the unity of military high command during the Roman Republic. In order to illustrate the (sometimes rather subtle) distinctions that existed between commanders with a nominally equal imperium, the author aims to examine the principle of the summum imperium auspiciumque and its underlying structures.

While the first three chapters establish some basic assumptions (the distinction between imperium and auspicia; the unity of the high command symbolized by the alternation of the consular fasces; the connection between summum imperium and provincia), the main part of the book consists of three case studies. Ch. 4 focuses on the highly controversial and much debated issue of triumphal law and the question of which commander was entitled to claim a full public triumph in case a victory was achieved by two or more generals. Against Mommsen, V. argues that the triumph was not an exclusive prerogative of the summus imperator. The main precondition was a formally independent imperium that could also be held by a subordinate general acting under the auspices of the commander-in-chief. The hierarchy of victorious generals was not subject to a systematically elaborated formal law but rather determined by a set of ‘some remarkably persistent qualifications and customary laws, never abandoned before the end of the Republic and the coming of monarchy’ (119).

Chs 5 and 6 deal with the hierarchy of magistrates in the provinces, namely the relations between consul and proconsul (151–92) and between several magistrates administering the same provincia (198–213). V. underlines again that, besides the existing statutory regulations, the impact of factors such as tradition, social rank or auctoritas have to be taken into account in order to understand the complex workings of Republican government. Ch. 7 traces the gradual monopolization of the summum imperium auspiciumque by powerful individuals during the late Republican period. According to V., this process, which sidelined the Republican principle of the consular summum imperium, ended in 27 b.c. with the Augustan provincial settlement. In a marked contrast to the mainstream of scholarship on the institutional framework of the Augustan principate, V. contends that already at this point the princeps was provided ‘with the supreme command “in alienis prouinciis”, viz. the summum imperium auspiciumque in what legally remained provinces assigned to, and governed by, other imperators’ (256).

Time and again V. reverts to two central methodological premises. First, he emphasizes that a study on such a fundamental issue as the high command in a heavily militarized society cannot only rely on an analysis of legal regulations and formal procedures, but also has to take into consideration the ‘structural and informal determinants of Roman social and political life’ (14) as well as mental dispositions, traditions and aristocratic values. This is certainly true and a principle that has been neglected too often in studies on Roman institutional history in the past. At the same time, however, this premise entails the fundamental question of the significance of legal regulations for political practice. On the one hand, V. asserts that there were some ‘paramount principle[s] of Roman public law’ (185), either written or unwritten. On the other hand, he repeatedly underlines (for example, 123, 157, 199) that even those legal principles could be suspended at any time by the Senate and People of Rome, were subjected to informal factors like social rank and auctoritas, and were ‘altered or abandoned as conditions changed’ (119). Since the evidence shows that Roman public law could indeed be very flexible and adjusted as the situation required, it has to be considered whether statutory and customary law actually determined the protagonists’ actions (as V. seems to assume in the end) or was rather used as an argument in political debates to bolster specific claims in advance and legitimize certain actions in retrospect.

Second, V. characterizes his study as ‘an old-fashioned, cautiously positivist, empirical and evidence-based enquiry’ (16), thereby rightly relativizing the excessively sceptical position taken by Mary Beard and others with regard to the value of the historiographical sources. At times, however, this approach leads to problematic conclusions, especially regarding the reconstruction of the early Republican conditions on the basis of Livy. In his discussion of the decemviri legibus scribundis (36–9) for example, V. seems to take Livy's account at face value. Yet it might be asked if the historian's remark that on the ides of May 450 b.c. all of the decemviri came to the forum with lictors holding the fasces and that this constituted a ‘sign of terror’ (3.63.3) should rather be seen as a comment within an early imperial (anti-)monarchic discourse.

V.’s command of both sources and modern scholarship is remarkable. With meticulous precision (although sometimes in overlong footnotes that diminish the book's readability and might have been better as appendices) the author illustrates the state of research for every issue he addresses and provides in-depth discussions of the respective passages. Unfortunately, given the abundance of cited primary texts, the volume goes without an index of sources. These caveats notwithstanding, V. has produced a highly substantial and lucidly argued contribution to the understanding of Roman institutional history, which provides ample material for further debate.