War has afflicted the life of mankind in this century as it has done in no other. The First World War killed ten million people, the Second fifty million, and wars since 1945 have killed millions more. Nuclear weapons, a product of the Second World War, have the potentiality not only to destroy lives on a scale greater than any yet explained or even imagined but to obliterate organised society itself. Because the story of war is intertwined with that of mankind from the earliest recorded times, no short book can encompass its whole history. John Keegan therefore concentrates in significant themes: the impact of war on our century and the forms it has taken; the origin of war in human nature and history; the adoption and use of war by states as an instrument of policy; the experience of war by individuals and human groups and its effect on their existence; and, finally, the future of war, particularly the question whether there can now be an end to it.