War has been one of the key institutions of the practice of international relations, and has always been a central focus of the study of international relations. In the post-cold war period many observers have suggested that the nature of war is undergoing fundamental changes, or even that in some parts of the world at least, it has become obsolete. With the advance of economic interdependence through globalization, and the spread of democracy, some groups of states seem to have formed security communities where war between them is no longer a possibility.
Elsewhere, however, war has continued to exist, and to take a number of different forms. For some countries, such as the United States, the use of advanced technology to achieve dramatic victories against conventional armies has led to suggestions that a revolution in military affairs is under way. Other parts of the world, however, have been characterized by warfare in whichnon-state actors have been prominent, the military technology employed has been relatively unsophisticated, and atrocities have been commonplace. Such new wars, it is argued by many, are a direct result of the process of globalization.
War has not disappeared as a form of social behaviour and shows no signs of doing so, though it is not necessarily an inevitable form of human behaviour and seems to have become ef ectively extinct in some parts of the world. Since the end of the cold war, the annual number of wars, the number of battle deaths, and the number of war-related massacres have all declined sharply compared with the cold war period. Between 1989 and 1992 nearly one hundred wars came to an end, and in terms of battle deaths, the 1990s were the least violent decade since the end of the Second World War (University of British Columbia, Human Security Center 2005: 17).
Despite the overall decline in the incidence of war, however, in many regions it is very much present and is displaying some novel features in comparison to those typical of the cold war period. In the contemporary world there are powerful pressures producing changes to national economies and societies. Some of these can be seen to rel ect the impact of globalization, others are the result of the broader ef ects of post-modernity, but their cumulative ef ect has been to bring about signii cant political and social changes, which have in turn been rel ected in changed perceptions of the nature of threats coming from the external environment. is in turn has inl uenced beliefs regarding the utility of force as an instrument of policy, and the forms and functions of war. In the past two centuries, the ‘modern’ era of istory, war has traditionally been seen as a brutal form of politics, a way in which states sought to resolve certain issues in international relations, and an outcome of their willingness to amass military power for defence and deterrence, and to project it in support of their foreign and defence policies. e two ‘world wars’ of the twentieth century typii ed this approach to the instrumentality of war. In the post-cold war period, the kinds of threats that have driven the accumulation of military power in the developed world have not taken the form of traditional state-to-state military rivalry, but have been a response to rather more amorphous and less predictable threats such as terrorism, insurgencies, and internal crises in other countries that seem to demand the projection of military force to resolve them.
For some observers, the current era has seen a major evolution in the structure of international relations, with the dramatic political changes that followed the end of the cold war and the dissolution of the Soviet Union. Changes in the international system on this scale are not common in history, and when they occur can be expected to have a major impact on the mechanisms by which the international system is governed.
At the same time, and partly as a result of the evolution of the international environment, changes are also occurring in the domestic attributes of many of the states that make up the international system. h ere has, for example, been a notable increase in the number of democratic political systems, but in the same period many other states have disintegrated into civil wars and insurgency. he identity of the key players in international relations has also changed since the end of the cold war. h e world has become temporarily subject to the hegemonic control of a single state,