The existing literature on the causes of war provides several fragments of a general theory, many of which have some empirical support
One of the longest and most heated debates about the causes of war concerns the effects of capitalism. Beginning with Adam Smith, liberal economists have argued that capitalism promotes peace. Marxists, by contrast, suggest that capitalism leads to frequent imperialist wars. Liberal economic theories point to the wealth generated by laissez-faire capitalist economies, the interdependence produced by trade, and the death and destruction of assets caused by war. Since capitalism has increased both the benefits of peace (by increasing productivity and trade) and the costs of war (by producing new and better instruments of destruction), it is no longer rational for states to wage war. The long period of relative peace that followed the triumph of capitalism in the nineteenth century and the two world wars that came after the rise of protectionist barriers to free trade often are cited in support of liberal economic theories, but those facts can be explained by hegemonic stability theorists as a consequence of the rise and decline of British hegemony.
In contrast to the sanguine views of capitalism presented by liberal economic theories, Marxists argue that economic problems inherent in advanced capitalist economies create incentives for war. First, the high productivity of industrial capitalism and a limited home market resulting from the poverty of the working class result in chronic ‘‘under consumption’’. Capitalists thus seek imperial expansion to control new markets for their goods. Second, Lenin argued that capitalists fight imperialist wars to gain access to more raw materials and find more profitable outlets for their capital. These pressures lead first to wars between powerful capitalist states and weaker peripheral states and then to wars between great powers over which of them will get to exploit the periphery.
In contrast to the stress on the political causes (power and security) of war in most theories, the Marxist theory of imperialism has the virtue of drawing attention to economic causes. However, there are several problems with the economic causes posited in theories of imperialism. Like most Marxist arguments about politics, theories of imperialism assume that states are controlled directly or indirectly by dominant economic classes and thus that state policies reflect dominant class interests. Since states are often free of dominant class control and since many groups other than capitalists often influence state policies, it is simplistic to view war as a reflection of the interests of capitalists. Moreover, in light of the arguments made by liberal economists, it is far from clear that capitalists prefer war to other means of expanding markets and increasing profits.
With the increasing globalization of economies and the transition of more states to capitalist economies, the debates about the effects of capitalism, trade, and imperialism on war have become increasingly significant. If Adam Smith is right, the future is likely to be more peaceful than the past, but if Marxist theorists are right, there will be an unprecedented increase in economically based warfare.
The form of government in a country also may determine how often that country initiates wars. Some sociologists argued that democratic states (with constitutions and separation of powers) initiate wars less often than do autocratic states. This conclusion follows from an analysis of who pays the costs of war and who gets the benefits. Since citizens are required to pay for war with high taxes and their lives, they will rarely support war initiation.
Rulers of states, by contrast, have much to gain from war and can pass on most of the costs to their subjects. Therefore, when decisions about war are made only by rulers (in autocracies), war will be frequent, and when citizens have more control of the decision (in democracies), peace generally will be the result.
Empirical research indicates that democratic states are less likely than are nondemocratic states to initiate wars, but the relationship is not strong. Perhaps one reason for the weakness of the relationship is that the assumption that citizens will oppose war initiation is not always correct. Many historical examples indicate that in at least some conditions citizens will support war even though it is not in their economic interest to do so.
Nationalism, religion, ethnicity, and other cultural factors often are cited as important causes of particular wars in journalistic and historical accounts, but there still is no general theory of the conditions in which these factors modify or even override economic interests. Many classical sociological arguments suggested that these ‘pre modern’ and ‘irrational’ sources of war would decline over time, but the late twentieth century has demonstrated the opposite. Nationalist and ethnic wars have become more common and intense. This raises the general issue of the factors affecting the choices individuals make about war initiation: Can these factors be modeled as rational maximization of interests, or is the process more complex?
Although the assumptions may be only implicit or undeveloped, all theories of war must contain some assumptions about individual decision making. However, few theories of war focus on the individual level of analysis. One notable exception is the rational-choice theory of war developed and tested by Bueno do Mesquita (1981). He begins by assuming that the decision to initiate war is made by a single dominant ruler who is a rational expected-utility maximizer. Utilities are defined in terms of state policies. Rulers fight wars to affect the policies of other states, essentially to make other states’ policies more similar to their interests. Rulers calculate the costs and benefits of initiating war and the probability of victory. War is initiated only when rulers expect a net gain from it.
This parsimonious set of assumptions has been used to generate several counterintuitive propositions. For example, common sense might suggest that states would fight their enemies and not their allies, but some political scientists argue that war will be more common between allies than between enemies. Wars between allies are caused by actual or anticipated policy changes that threaten the existing relationship. The interventions of the United States in Latin America and of the Soviet Union in eastern Europe after World War II illustrate the process. Other counterintuitive propositions suggest that under some conditions a state may rationally choose to attack the stronger of two allied states instead of the weaker, and under some conditions it is rational for a state with no allies to initiate a war against a stronger state with allies (if the distance between the two is great, the weaker state will be unable to aid the stronger). Although these propositions and others derived from the theory have received strong empirical support, many have argued that the basic rational-choice assumptions of the theory are unrealistic and have rejected Bueno de Mesquita’s work on those grounds.
Other analyses of the decision to initiate war focus on how the social features of the decision making process lead to deviations from rational choice. Furthermore, all political decisions are made within organizations and that this setting often influences the content of decisions. The standard operating procedures and repertoires tend to limit the flexibility of decision makers and make it difficult to respond adequately to novel situations. Sociologists also focus on the small groups within political organizations (such as executives and their cabinet advisers) that actually make decisions about war. He suggests that the cohesiveness of these small groups often leads to a striving for unanimity that prevents a full debate about options and produces a premature consensus. Other scholars have discussed common misperceptions that distort decisions about war, such as the tendency to underestimate the capabilities of one’s enemies and overestimate one’s own. In spite of these promising studies, work on deviations from rational choice is just beginning, and there still is no general theoretical model of the decision to initiate war.
The failure to develop a convincing general theory of the causes of war has convinced some scholars that no such theory is possible; that all one can do is describe the causes of particular wars. This pessimistic conclusion is premature. The existing literature on the causes of war provides several fragments of a general theory, many of which have some empirical support. The goal of theory and research on war in the future will be to combine aspects of arguments at all three levels of analysis to create a general theory of the causes of war.