It can be said at once that this is a most important book that fills a significant gap in the literature for a study of the Roman Empire. This gap is not so much in the history of Rome and her frontier wars — the context in which frontiers were established — but in the actual installations and character of the frontiers themselves. It is also difficult to think of anyone except for Breeze himself who could have filled the gap. And the frontiers themselves are surely worthy of study — as the author himself points out, after the famous network of Roman roads, with a length of 7,500 km (4,800 miles), together they form the single largest monument surviving from the Roman World. The omission is all the more odd as Roman Frontiers Studies — Limesforschung — is a sub-field of Roman provincial history/archaeology in its own right and the subject of sustained archaeological activity in the relevant provinces of the Empire and of regular international congresses of which there have been no less than twenty, from the first established under the initiative of Eric Birley in 1949, to the Madrid Congress of 2009.

Like Gaul, B.'s work is divided into three parts: Part I – The Sources; Part II – The Frontiers themselves — the core of the book which is discussed below; Part III – Interpretation/ Discussion; this analytical element is subdivided into five sections: (1) Development; (2) Military deployment; (3) How frontiers functioned; (4) Defences behind frontiers; (5) Roman imperial frontier policy. At the end there is a short section on conclusions.

Part II is divided into ‘type’ of frontier: i.e. linear barriers, and river, desert, mountain and sea frontiers — including the defences of the Saxon Shore. Within these divisions individual frontiers are treated chronologically. This is an interesting arrangement which facilitates the typological comparison of, say, Hadrian's Wall with the land frontier in southern Germany. However, this is not the only possible arrangement and has one disadvantage in that certain frontiers could come into more than one category, e.g. the Fossatum Africae both as a linear frontier and a desert frontier. One could have chosen to deal with the frontiers geographically — the various Roman frontiers in Germany for example — or chronologically. On occasion the Romans themselves did both, or at least considered the legionary establishment that supported the frontiers in these ways, cf. Tacitus, Annals 4.5 reviewing the situation under Tiberius, and the inscription listing the frontier legions (ILS 2288, dated to pre-a.d. 165 but with additions). These sections in Part II on the various frontiers can, despite the provision of maps, make rather difficult reading at times unless one is familiar with the relevant place names, but this will have been inevitable.

The conclusions are followed by sections on Further Reading, guides to different frontiers, DVDs and sites to see — all most useful additions. The final sections are the notes to the main body of the text and the index. The notes (226–33) are naturally arranged chapter by chapter, though again, as in the section on Further Reading, the chapter numbers are omitted. Another technical point making use of the notes less easy than it might otherwise be, is that works cited in the footnotes are often given in abbreviated form and can be hard to track down — e.g. for the expansion of ‘Wooliscroft 2001’ (note 15 on p. 77), which is not given in the footnote itself (228), one turns first to the bibliography for the relevant chapter, and then failing that, to the bibliography for other chapters before finally finding it in the bibliography to the introduction.

These technical niggles hardly detract from what is a huge achievement and we are fortunate indeed to have at last a full and authoritative survey of the frontiers of the Empire and their associated frontier works.