Historians have written extensively and powerfully on individual civil wars, Irish ones included. But the reading of civil wars as such has more frequently involved lenses that have been designed by other disciplines. There has, for example, been no synoptic study by an historian that has been as influential within this field as Stathis Kalyvas’s magisterial 2006 book, The logic of violence in civil war. Perhaps that will now change. For David Armitage’s Civil wars: a history in ideas deserves to be seen as a work every bit as necessary to a full understanding of its topic as is Kalyvas’s brilliant book.

What Professor Armitage sets out to do, in a deeply erudite and compelling study, is not to provide ‘an overarching theory of civil war’ (p. 7). In exploring civil wars and their associated ideas, he stresses instead the contingent, complex, explicable and fluid dynamics that are involved in this Protean phenomenon; ‘The benefit of history,’ he writes, ‘is the knowledge that civil war has never been quite as stable or transparent a category as its popular usage would imply’ (p. 15).

The book interrogates civil wars’ ‘multiple pasts’ (p. 16), and it recognises the problems that exist with definition: ‘Only by ignoring the multiple histories of civil war would it be possible to define it. For history shows that civil war has had no stable identity or agreed definition’ (p. 18). This is very much ‘big picture’ (p. 20) history: a work which bravely attempts comparison over long periods, and which addresses a major global phenomenon rather than being satisfied with commanding only its constituent components.

Professor Armitage proposes that we consider three turning points in the history of civil wars: the late eighteenth century, when people sought to distinguish between civil war and revolution; the mid-nineteenth century, with efforts to establish a legal meaning for the term; and the latter period of the Cold War, when social scientists tried to understand associated global conflicts. His book traces the history of the idea of civil wars, from ancient Roman origins to contemporary Syria.

Along the way, Armitage evinces scepticism about social-scientific endeavours to bring ultimate conceptual clarity to the analysis of civil war. If the Romans were the first to identify conflicts as civil wars, then ensuing centuries have produced a palimpsest of understandings which have also remained contested at any particular historical moment.

And his historian’s approach offers rich rewards. Professor Armitage is sceptical about some attempts ‘to confine civil war within a single definition’ (p. 238), and might lead us to reflect on how this book can illuminate some Irish historical experience. One possible area would involve the Northern Ireland Troubles of the late-twentieth and early-twenty-first centuries. Was this a civil war? Against some of the Procrustean measures that have been deployed by social scientists, no; the levels of killing would rule the Troubles out of some such assessments, for example, through their simply being too low. But much of what this compelling book describes in the many histories of civil wars – conflict between very familiar enemies, between fellow citizens, between people battling against their neighbours and intimates within a single political community; wars in which contending parties have disputed the established legitimacy of one actor within those boundaries, in conflicts which are cyclical, recurrent and sequential – much of this identifies crucial aspects of the deep nature of the Northern Irish Troubles. Many of those involved in that conflict resisted and still resist the designation of that blood-stained period of Ulster’s history as a civil war. Armitage’s book, among its many other merits, hints that much illumination might be secured by framing it in just those terms.

Also of great value is Bill Kissane’s new book, Nations torn asunder: the challenge of civil war. Professor Kissane has already written valuably on the Irish civil war itself, and this wider-angled study aims to evaluate and summarise the scholarly literature of recent decades on civil war as such. As with Kissane’s other work, there is a welcome blend of the social-scientific with the historical, and the book is all the richer for that. The recurrent, sequential quality of civil wars is again noted (p. 12), as is the tendency for people persistently to view them negatively (p. 25) (far more so, say, than with the term ‘revolution’). And there is much sharp-eyed assessment: Kissane is, for example, lucid on the failings of much of the ‘new wars’ literature. And his ambitious Epilogue to the book unveils wider patterns of approach (the profound division, for example, between explaining why conflicts emerge and understanding what happens to people when they then occur (p. 218)).

Kissane also points towards the need for focusing (more than many scholars do) on the state as such, when we think about civil wars. This seems to me a vital point. Professor Kissane raises it again in the Introduction to his edited collection, After civil war: division, reconstruction and reconciliation in contemporary Europe, where he points to the significance of political legitimacy after civil war, as one of the key issues for subsequent states.

Nations torn asunder reflects an author who is admirably aware of the need for historically-oriented answers to questions relating to civil war. Kissane rightly notes that, ‘Historians are more likely to stress the specificity of individual conflicts’ (p. 27); but I think one of the many merits of his academic synthesis of scholarly work on civil wars is to remind even the most particularistic of scholars to think comparatively where that makes intellectual sense. This will not produce tidy patterns, and Kissane acknowledges the likely persistence of unpredictability in civil warfare (p. 90). But particularity and uniqueness are the foundations for cross-case comparison, rather than its enemies.