The events of September 11, 2001 have for the first time demonstrated to a wider public what studies of war had brought to light already some time ago. Since the end of World War II, war between states has become rare. The vast majority of wars today represent acts of violence between a state and a non-state actor/group. As this kind of modern war takes place mainly in Africa and Asia, it has hardly been taken note of by the European and North American public. Yet this dominant form of war since the middle of the twentieth century repeals the state’s monopoly on war that European states have largely been able to assert since the sixteenth century.
What does this repeal of a development, in the course of which the state became the bearer of the monopoly on legitimate violence (Max Weber), mean for historical research on war? The essay discusses this question taking two approaches: one asks for the significance of anthropological constants as regards the readiness of humans to wage war. Throughout the history of humankind, dehumanizing the enemy, for example, appears to have been an important presupposition to make humans ready to accept the killing of the other as legitimate. Rules of conduct that also applied and were observed during war are being invalidated against someone culturally different.
In a second approach, the essay asks for the change in conceptions and legitimization of war from the Middle Ages to the present. Particular attention is given to the question how the idea of the modern nation has changed the perceptions of war. The caesura in the legitimization of war that occurred around 1800, hitherto unsurpassed, has been put for the first time into a theoretical framework by Carl von Clausewitz. His theory, however, only applies to the kind of war that has become dominant in Europe and North America since the sixteenth century, i.e. the war between states. The wars of earlier times as well as the wars of the present do not conform to this type of war. To analyze them, interdisciplinary cooperation, in particular between historical and ethnological research, is necessary.