There can be few more important but also more contentious issues than attempting to understand the human propensity for conflict. Our history is inextricably tangled in wave after wave of inter-human fighting from as far back as we have records. Richard Overy draws on a lifetime's study of conflict to write this challenging, invaluable book. Studying every facet of war from biology to belief, psychology to security, Overy allows readers to understand the many contradictory or self-reinforcing ways in which warfare can suddenly appear a legitimate option. Repeatedly humans have foresworn war, have understood its appalling risks and have wished to create more pacific, productive societies. And yet almost inevitably circumstances emerge under which war once more seems inevitable or even desirable.