This book is the outcome of many years' thinking and writing about certain questions arising from the relationship between what we call civilization and war. For instance, why do different societies have different ideas about right and wrong behaviour in war? How did the system of international law which the European society of States evolved for itself and then disseminated all round the globe come to have at its heart a body of rules and principles for the proper conduct of wars, and why were they formulated just so? And, irrespective of whether it may have worked well or badly in times past, does this body of rules and principles in our own time successfully moderate the conduct of wars (armed conflicts, as many nowadays prefer to call them) as the theory of our civilization expects it to do?
It is with the third of these questions--not 'why do wars happen?' but 'what happens in wars?'--that this book is mainly concerned. War, in one form or another, is something of which many States, societies, and persons in our contemporary world have direct and, very often, unhappy experience. To all the others who are spared direct experience of it, war remains a subject of intense anxiety and interest because of the sympathy and indignation felt for its victims by onlookers, who moreover must often reflect that their own immunity might not last for ever. War and the risk of war are universally acknowledged to be, if not the outstanding shame and horror of our age, at least top-equal with the outstanding ones. It is precisely on that account that the parts of international law supposed to control and moderate it, the Laws of War as they were formerly known, have become, in our age, more highly developed than ever before and popularly known as International Humanitarian Law.
Law is not the only means by which the nastiness of war-conduct can be moderated, but it is a prominent one, deep-rooted in the history of our civilization and, it can be argued, rather an admirable one. The present generation has witnessed two big bursts of activity to enlarge and refine it: the first, directly after the Second World War; the second, in the 1970s, with debate about its merits still going on. Almost all armed forces profess to incorporate elements of it in their basic instruction, and some of them are known effectively to do so. So much attention is being paid to it in contemporary debate and reportage about the causes and conduct of wars that one may reasonably guess that more people are now aware of it (or, more likely, bits of it) than in any previous period of human history.