Richard Overy is the master historian of the Second World War and of what he calls the “morbid age” that preceded it. This book is his magnum opus (in every sense of the phrase). It is a commanding global history of the conflict that brings together its geopolitical and geostrategic elements with a stringent analysis of its many dimensions: the extraordinary level of mobilization the war demanded; the means by which it was fought; the “war economies” it created; the moral and legal issues it raised; the role of civilians; the varying emotional responses to the war and its impact on mental health; and the scale and nature of the crimes and atrocities that came in its wake. The book concludes with a chapter that argues (uncontroversially) that the war signalled the approaching end of the “old imperial order”, whose rules and norms had governed the world for the previous century. It needs adding, of course, that it was not the end of empire, as so many commentators at the time and since have naively imagined. Empire is a shape-shifting phenomenon that is always with us: new colonialisms arise as swiftly as the old disappear.

One of the many virtues of Blood and Ruins is to force us to question why a war on such an enormous scale and of such appalling barbarity should have broken out at this particular moment in world history. What, if anything, in the previous century had lit the fuse for such a cataclysmic conflict, far more bloody and destructive than the “war to end all wars” only twenty years earlier? Was the war the ghastly end-product of what Eric Hobsbawm once labelled the “dual revolution” – the industrial revolution in Britain, the political revolution in France – their volatile interaction and (eventually) globe-wide impact? Or was it (merely?) the latest and bloodiest in the series of wars for global supremacy that have punctuated world history since the seventeenth century – wars that can be checked for a while by hegemonic power or a grand coalition of the status quo, but follow inevitably when challengers appear, strong enough to remake the world to their own design?

Richard Overy’s answer, laid out in his first three chapters, is to see the war primarily as the final grand struggle of rival imperialists. Their aggressive expansionist imperialism, manifest from the later nineteenth century, was driven...