The central moral paradox of nuclear deterrence theory is that peace (a morally very desirable good) is preserved by each superpower's immorally threatening the lives of millions of innocent people on the other side. The victims are people who would probably not have approved of the conventional aggression or nuclear surprise attack that began a war, but who must bear the brunt of the retaliation that turns the war into our worst nightmares of World War III. The prospective suffering of such innocents, the prospective destruction of the cities in which they live, presumably deters their leaders from ever beginning such wars in the first place, i.e. deters the prospectively guilty from becoming the guilty.

Various proposals for alternatives to deterrence can be supported by practical arguments that they might actually improve the situation of Americans or others, as we balance all the contingencies against each other. Yet such proposals for disarmament, or for antimissile systems as in Reagan's Strategic Defense Initiative, or for a reliance on conventional defenses so as to limit nuclear weapons to deterring each other and nothing more (perhaps this is where the 1987 Reagan–Gorbachev INF Treaty is to take us?) all also stem in part from the moral problems of continuing to accept Mutual Assured Destruction.

Preventing crime by punishing the loved ones of those who would have become criminals is certainly an alien and distasteful idea for anyone accustomed to the cultural traditions of the Western world. We cannot think of anything else for which we use such a bizarre mechanism, except the preservation of peace in the years after 1945.

It is difficult to read both the theoretical literature in political science on the causes of war and historians' case studies of the origins of particular wars without being struck by the difference in their respective evaluations of the importance of domestic political factors. Whereas historians devote considerable attention to these variables, most political scientists minimize their importance. Domestic political variables are not included in any of the leading theories of the causes of war; instead, they appear only in a number of isolated hypotheses and in some empirical studies that are generally atheoretical and noncumulative. This gap is troubling and suggests that political scientists and historians who study war have learned little from each other. A greater recognition of the role of domestic factors by political scientists would increase the explanatory power of their theories and provide more useful conceptual frameworks for the historical analysis of individual wars.

This study takes a first step toward bridging this gap by examining some of the disparate theoretical literature on domestic politics and war. It examines the relationship between national attributes and war behavior, the relative likelihood of democratic and non-democratic regimes going to war, Marxist and liberal theories regarding the impact of economic structure, the influence of nationalism and public opinion, and the scapegoat hypothesis. First, however, this article takes a closer look at the different treatment of domestic sources of war by political scientists and historians.

Are there really lessons of the past? The past is certainly a source of knowledge, our only source of knowledge given the flow of time, but, strictly speaking, it does not teach lessons. By lessons I mean maxims for attaining particular outcomes in the present or future: for example, Si vis pacem, para helium, or it is better for a prince to be feared than loved. Insofar as these maxims seem to offer guidance for policymakers, they are usually psychological, not historical. They supposedly summarize human traits that persist regardless of changing historical contexts. Other examples might include the notion that appeasement encourages aggression or that “military decision makers will tend to overestimate the feasibility of an operational plan if a realistic assessment would require forsaking fundamental beliefs or values.” Identification of such allegedly constant traits was the goal of philosophical history and may have seemed an appropriate program for historians during the Enlightenment and their policy-studies heirs. Subsequent historians, however, have usually sought to describe changing societal contexts or outcomes.

“A war nobody wanted” goes to the heart of a pathological puzzle that energizes our analyses of crises. Where nobody's interest is served, are we not required to lament and condemn all of the decision-making and policy processes that are involved? “War serves the interests of no one” has been a staple of many a sermon and commentary in the past; it is today an even more persuasive and plausible synopsis during any crisis that forces us to contemplate what modern weapons can do.

Thus, we will not treat a “crisis” simply as an enhanced likelihood of war, for this definition may be both too narrow and too broad. It may be too narrow in that it excludes the analogous family tensions and other human encounters where the worst each side can inflict on the other is far less than war, but where much of the same game of mutual risk-taking is at work. It may be too broad (even though much of popular usage might include all risks of war as crises) in that it draws in cases where no contest of wills is in place, and where neither side is betting its position on estimates of the other side's resolve. For example, if India loses its patience with the Portuguese and, minimizing costs all around in the process, tells its military to seize Goa, is the enhanced likelihood of war immediately prior to the seizure really a part of what we need to analyze in this article?

Explanations of the origins of World War II tend to emphasize either deliberate, if failed, choices or inexorable processes. The first view indicts Adolf Hitler's aggrandizing choices and preference for violence, and questions the judgment and strategy of the appeasers, personified, correctly or not, by Prime Minister Neville Chamberlain. The second view broadens the focus, pointing to secular changes in relative power between states; to the relation between states' commitments and their ability to uphold and protect them; and to domestic, economic, and cultural dynamics that individually, or in combination, predisposed the situation to conflict. Attention to both dimensions is necessary to appreciate Britain's strategy as the central axis of diplomacy and rivalry with Germany in the 1930s and to distill the “lessons” of the origins of the war.

In the 1930s, Britain took over the mantle of maintaining the status quo vis-à-vis Germany. Chamberlain and his associates faced the classic issue of judging the nature of its adversary's ambitions. Morgenthau captured the dilemma for Britain in this period: “While it would be fatal to counter imperialistic designs with measures appropriate to a policy of the status quo, it would be only a little less risky to deal with a policy [of an adversary] seeking adjustments within the status quo as though it were imperialistic.”

Among the major wars of modern European history, the Thirty Years' War stands out not only for its duration but also for its striking impact on the international system in which it took place. Before 1618, the Spanish Habsburgs were the central power in a Europe where religious differences were crucial. The war and its Franco-Spanish extension ended in 1659. By that time, France and other nations had increased their power, and religion played a much less important role in defining alliances. Moreover, Europe's center had moved east, as Russia, Prussia, and the Austrian Habsburgs became more powerful.

The war's origins are well known. Conflict in the Holy Roman Empire, especially in the Habsburg lands, over religion and over the power of the emperor provoked a civil war in Bohemia in 1618. The Bohemian war both resurrected and created a network of alliances which caused the conflict to continue into the 1620s. The opportunities offered by the disruption in Germany led the Danes to invade in 1625, and the Swedes and French to intervene in the 1630s, which continued the war by bringing in fresh combatants. The result was a conflict that could not be controlled by the Bohemians and the emperor, who had begun it. They were not allowed to extricate themselves until they had completely exhausted themselves and everyone else; as fitting compensation, the Bohemians and the emperor were important losers.