The overall approach of the book is thematic, with the Introduction providing important context for what follows, especially for those less familiar with Roman history, first by defining key terms and parameters (especially explaining the chronological range of the volume, from the fourth century BC to the early seventh century AD), and then through an overview of the incidence of warfare, both external and internal, across the course of Roman history. The evolution of Roman military forces from the Republic through to Late Antiquity is outlined, with particular attention to Augustus’ formalisation of a standing army and the reconfiguration of the empire’s forces in the early fourth century. Finally, the most important ancient sources for the subject are introduced, with discussion of key literary sources (Polybius, Caesar, Livy, Josephus, Tacitus, Ammianus Marcellinus and Procopius), the less familiar Syriac chronicle atttributed to Joshua the Stylite, military treatises, documentary evidence (inscriptions, papyri) and relevant archaeological material.