The First World War created the modern world. A conflict of unparalleled ferocity far beyond its European epicentre, it broke the century of relative peace and prosperity which we associate with the Victorian era. It unleashed both the demons of the twenieth century - pestilence, military destruction and mass death - and the ideas which continue to shape our world today - modernism in the arts, new approaches to psychology and medicine, and radical ideas about economics and society. An event of this scale and complexity needs a great historian to portray it, and in his new book, John Keegan fulfils a life-long ambition to write the definitive book on the war. It was of course foremost a fascinating new interpretations of the military events. But the war also acted as a formidable engine for social change throughout the world, and this too is brilliantly conveyed in Keegan's fascinating and magisterial work.