L’armée de Gaule sous le Bas-Empire fut une des trois armées principales de l’Empire romain. Son évolution de la fin du IIIe siècle jusqu’au début du Ve fut marquée par une réorganisation graduelle dans le commandement, ainsi que dans l’organisation des troupes et des fortifications. Ces réformes ont fait l’objet d’études qui ont dressé un schéma de déploiement des troupes resté longtemps populaire. À ce schéma s’est ensuite ajoutée l’idée de la stratégie à grande échelle qui y aurait été associée. Ce mémoire tâche de dresser une synthèse des derniers travaux sur l’armée romaine tardive en Gaule. L’approche choisie repose sur une réévaluation des sources sans l’influence d’un schéma défensif préconçu, ainsi que sur une critique de certaines idées reçues concernant l’armée romaine du IVe siècle. / The army stationed in Gaul during the Later Empire was one of the three main armies available to the Roman Empire. Its evolution from the late IIIrd century to the early Vth century was marked by reforms applied gradually to the high command, and to the organization of troops and fortifications. These measures have interested scholars who established a model of troop deployment which enjoyed great popularity over a long period of time. The idea of strategy applied on a great scale was later included in this concept. This thesis proposes a synthesis of the latest research on the late Roman army in Gaul. The selected approach of analysis is based on a reevaluation of the sources without the bias of a preconceived defensive model. Some obsolete ideas regarding the late Roman army will also be subject to criticism.

This thesis investigates representations of dynastic legitimacy and imperial power in the later Roman Empire (AD 284-337). It explores the continuity and change in expressions of dynastic legitimacy by, for and about the emperors of this period, which were presented in coinage, panegyrics, and other literary and material evidence. I argue that familial relationships were used throughout this period to make legitimation claims or to counter claims made by rivals, rejecting the notion of clear breaks between the third century, the Tetrarchy and the reign of Constantine. The Tetrarchy’s creation of familial links through adoption and marriage led to a web of inter-familial relationships that they and later emperors used in promoting their own claims to imperial legitimacy. At the same time, the presentation of these imperial colleges as harmonious co-rulership relied heavily on the adaptation of pre-existing strategies, which in turn would be adapted by the emperors of the early fourth century. This thesis proceeds roughly chronologically, focusing on the regimes of individual emperors and their collaborators when possible. Chapter 1 examines the creation of the Tetrarchy as an extended ‘family’ and the adaptation of ideologies of third-century co-rulership. Chapter 2 explores the changes in the Second Tetrarchy, with an especial focus on the ‘Iovian’ family of Galerius and Maximinus Daza. Chapter 3 looks at Maxentius’ claims to both ‘retrospective’ and ‘prospective’ dynastic legitimacy. Chapter 4 examines Licinius’ legitimacy both as a co-ruler and brother-in-law of Constantine, and as the beginning of a new ‘Iovian’ dynasty. Chapter 5 delves deeper into the different claims to dynastic legitimacy made by Constantine over the course of his thirty-year reign. Taken together, these chapters offer a new approach by arguing against the dichotomy between ‘dynasty’ and ‘collegiality’ that tends to dominate scholarship of this period. Instead they focus on the similarities and continuities between the representations of imperial families and imperial colleges in order to understand how perceptions of dynastic legitimacy evolved in the third and fourth centuries.

L’armée de Gaule sous le Bas-Empire fut une des trois armées principales de l’Empire romain. Son évolution de la fin du IIIe siècle jusqu’au début du Ve fut marquée par une réorganisation graduelle dans le commandement, ainsi que dans l’organisation des troupes et des fortifications. Ces réformes ont fait l’objet d’études qui ont dressé un schéma de déploiement des troupes resté longtemps populaire. À ce schéma s’est ensuite ajoutée l’idée de la stratégie à grande échelle qui y aurait été associée. Ce mémoire tâche de dresser une synthèse des derniers travaux sur l’armée romaine tardive en Gaule. L’approche choisie repose sur une réévaluation des sources sans l’influence d’un schéma défensif préconçu, ainsi que sur une critique de certaines idées reçues concernant l’armée romaine du IVe siècle. / The army stationed in Gaul during the Later Empire was one of the three main armies available to the Roman Empire. Its evolution from the late IIIrd century to the early Vth century was marked by reforms applied gradually to the high command, and to the organization of troops and fortifications. These measures have interested scholars who established a model of troop deployment which enjoyed great popularity over a long period of time. The idea of strategy applied on a great scale was later included in this concept. This thesis proposes a synthesis of the latest research on the late Roman army in Gaul. The selected approach of analysis is based on a reevaluation of the sources without the bias of a preconceived defensive model. Some obsolete ideas regarding the late Roman army will also be subject to criticism.