Putting the Democratic Peace Theory to the Test

After the collapse of USSR, the Cold War ended up with the triumph of democracy. Liberal democracy has spread from West Europe and North America towards a much wider range of area. The celebration of democracy seems to signal the coming of a new bright era of human history. Fukuyama (1992: xi) even optimistically argued that democratic liberalism may become ‘the end point of mankind’s ideological evolution’ and the ‘final form of human government’ in his book the end of history and the last man.

Another controversial claim about liberal democracy is the thesis of democratic peace which proposes that liberal democracies rarely have militarised disputes or go to wars with each other. Some scholars firmly believe this argument while some others suspect that the democratic peace thesis is merely one of the ‘several decades of empirical research that has failed to produce a single meaningful law like generalization in international relations research’ (Maoz, 1997: 163).

This essay seeks to analyze the validity of one of the related hypotheses of democratic peace: the more liberal democratic the dyad of state, the less likely the dyad is to go to war or has militarised disputes. I am going to argue that this proposition is correct because it is not only supported by adequate empirical evidence, but also supported by logically coherent theoretical analysis.

Liberal Democracy as a Continuum

The emergence of the notion and practice of democracy can be traced back to the first golden era of western civilization. As early as 508BC, Cleisthenes successfully implemented a democratic reform in Athens by creating Council of 500, which ‘with its rotating membership and restrictions on re-election, succeeded in extending political participation in an organized way across the entire geographical sweep of Attica’ (Hornblower, 1992: 9).

However, the modern thinking of liberal democracy began to form mainly during the Age of Enlightenment, when the Enlightenment philosophers started to propose the equality and liberty of human beings as the principles of organizing the society. Immanuel Kant advocates that the form of republican government is required by the progress of history, and the freedom of human beings ‘can be realized only when there is representative body to constrain the executive powers of the state’ (Gaubatz, 1996: 138).

While the core value of liberal democracy based on the old time wisdom is widely understood, the debates over the question of what exactly it is has even become fiercer. The definition and implications of liberal democracy is vital because without it the analysis of all related issues will be impossible. One productive definition was given by Schumpeter (1954: 269), who declared that ‘the democratic method is that institutional arrangement for arriving at political decisions in which individuals acquire the power to decide by means of a competitive struggle for the people’s vote’. This definition demonstrates clearly how people’s rights and power can be realized through the democratic mechanism.

However, while this definition correctly points out the characteristics of liberal democracy from institutional perspective, it is still incomplete because it ignores the spiritual aspects of liberal democracy. Liberal democracy is not only a material institution; it is also a complex of ideas and perceptions reflecting the value and spirit of liberalism. In this sense, Oven (1994: 89) has made a good complementation to the inadequate definition of Schumpeter. Oven argues that from liberal perspective, people have universal interests to pursue peace and freedom, which is the precondition of achieving higher individual well-being, and the democratic institutions will be the tools of realizing those norms.

Synthesizing the analysis above, a more comprehensive definition of liberal democracy can be given. Liberal democracy is a complex myriad of:

(1)A set of institutions, through which the rights and powers of citizens will be realized by the decision makers who are chosen to represent the whole people. Some examples of these institutions and mechanism are the fair and competitive campaigns, the separation of powers and certain degree of political participation.

(2) A series of liberal norms, which emphasize the equality of human beings, the freedom of individual to pursue his happiness and well-being and the legal right to defend the order and justice in the society.

In addition,  liberal democracy should be considered as a continuum rather than a dichotomy. Liberal democracy is a dynamic organism which will continue to evolve as long as it has a foundation to exist. So when considering the degree of liberal democracies, I can take a look at the degree of the two aspects of liberal democracy because the changes of these aspects will lead to the changes of liberal democratic degree. This is the basis of the theoretical analysis in this essay.

The Empirical Test of the Correctness of the Proposition

There have already been a lot of empirical researches which aimed at testing the validity of democratic peace. One of the most influential was conducted by Maoz and Russett (1993: 625) in their Normative and Structural Causes of Democratic Peace, 1946-1986. This research involved a testing of one hypothesis: ‘The more democratic are both members of a pair of states, the less likely it is that militarized disputes break out between them, and the less likely it is that any disputes that do break out will escalate’. Their statistical results show that the degree of democracy, as the independent variable, has a strongly negative effect on the possibility of outbreak and escalation of militarized disputes and international crises.

Here I conduct another simple test which covers a wider range of period from two databases: Polity IV Project: Political Regime Characteristics and Transitions, 1800-2009 (Marshall, 2009) and the newest Correlates of War dataset (COW, 2010). Polity IV Project provides a wide range of degree of democracy based on a definition which is similar to that given above but with more specific details, such as the degree of competitiveness of executive recruitment and the competitiveness of political participation. By seeing the degree of democracy in both sides of the wars and militarized disputes, the hypothesis of ‘the more liberal democratic the dyad of states the less likely that dyad is to go to wars or have militarized disputes’ can be tested.

The result of the test of the wars is strongly positive. In the Polity IV dataset, a country can be identified as a democratic regime when its score in the “Polity” category is not below 6, so a dyad of liberal democracy must be one in which either sides score should be 6 or above. According to the COW project, from 1816 to 2007, there have been 95 inter-state wars around the world, but none of them happened between two countries which at least got a score of 6 in Polity IV. So if Marshall’s score of regimes is credible, it is true that the more liberal democratic the dyad is, the less likely that dyad is to go to war, because even the dyad with the lowest degree in the continuum of liberal democracy has no record of launching war against each other.

In terms of militarized disputes, I use the MID v3.1 dataset (COW, 2007) which includes all the interstate militarized disputes from 1816-2001. This test shows confusing result. According to the MID v3.1, there have been 4,344 inter-state militarized disputes around the world, but there are only 118 happened between two nations with minimum score of 6 in Polity IV, that is 2.7% of total. More specific category of the frequency of inter-state militarized disputes according to the degree of liberal democracy of the dyads is shown in the table below. The degree of liberal democracy is calculated as the mean number of both sides’ scores in Polity IV:

Table 1: Degree of Liberal Democratic Dyads in Militarized Disputes

Degree of Liberal Democracy Number of Dyads
6-6.5 3
7-7.5 27
8-8.5 46(25)
9-9.5 22
10 20


The table seems to show that the militarized disputes are most likely to happen when the degree of liberal democracy is in the category of 8-8.5. But after careful examination, I find that the table has not told the full story. Although there 46 militarized disputes in the category of 8-8.5, 22 of them belong to the same conflict issue: the disputes of Turkey VS Greece and Cyprus. They are very special because the source of all these conflicts is Turco-Cypriot War of 1974, during which Greece was not a democratic nation yet. This series of conflicts was problems left over by history rather than various conflicts originating from the liberal democratic dyad, so all these conflicts concerned should at most only be counted as one conflict. After this modification, there will be 25 cases in category of 8-8.5, which means that the statistic does not contradict the hypothesis proposed. Some may also wonder why the lowest level of liberal democracy occupies the smallest share. The answer is that too many countries with the score of 6 are politically, geographically or militarily unimportant so that it is hard for them to have reasons to dispute with other liberal democracies. Examples of this include Botswana, Burundi, Fiji and Malawi. In contrast, most of the big players in international systems are positioned in the higher level of liberal democracy with a much wilder time span, such as France, United Kingdom and United States. So in total, after making the modification and giving the explanation of some points of the data, the statistic still shows that the number of the cases of militarized disputes declines as the degree of democracy becomes higher.

After the above analysis, I conclude that in general, the empirical data supports the claim that the more liberal democratic the dyad of states is, the less likely that dyad is to go to war or have militarized disputes, although the support for the militarized disputes is not as evident as that of wars. In the next part, I will attempt to give some underlying reasons to explain the correctness of this claim.

Theoretical Reasons

Although the empirical evidence supports the proposition, I still need to find the reasons behind these facts because just as Waltz mentioned, ‘[s] Statistics do not show how anything works or fits together. Statistics are simply descriptions in numerical form’ (Waltz, 1979: 3). Firstly, it will be beneficial to have a brief look at the whole international system. All countries are conducting their behaviors in a shared international environment and anarchy is the most crucial characteristic of it which means that ‘no centralized authority or ultimate arbiter that stands above states’(Mearsheimer, 2010: 79) and which creates a permissive environment for the aggressive behaviors. Both liberal democracies and non-liberal democracies coexist in the same anarchical system, but why liberal democracies rarely fight with each other and why, as the empirical evidence suggests, the more liberal democratic the dyad is the less likely that the dyad is to go to war or have militarized disputes? There must be some traits in the dyad of liberal democracy change the hostile nature of international system and the behavior pattern in the dyad to some extent. The more liberal democratic the dyad is, the bigger the changes are. The changes are shown below:

Chart 1: The Degree of a Liberal Democratic Dyad

Less Liberal Democratic                              More Liberal Democratic
Stronger Sense of Uncertainty                    Weaker Sense of Uncertainty

Lower Mobilization Cost of War                   Higher Mobilization Cost of War

Stronger Nationalism’s Effect                      Weaker Nationalism’s Effect

on Military Actions                                        on Military Actions

Weaker Shared Identity                               Stronger Shared Identity

In a prior section a definition of liberal democracy has been given, which can be regarded as a continuum with two important aspects: the democratic institutions and the liberal norms and ideas. It is from these characteristics that I can see more specifically what have been changed and how they have been changed, with the result that the proposition concerned is correct.

The Democratic Institutions

The institutional structure of liberal democracies leads to the direct result that it is relatively hard to mobilized militarized actions compared with an authoritarian regime or a militarily dictatorship, in which the governance of the nation ‘relies in the end upon the personality and resolve of the ruler’ (Silitski, 2009: 44), the elites or rulers can easily launch a war by using absolute powers. Some critics argue that democratic nations are at least as war-prone as the non-democratic ones. This is true because when facing a non-democratic country, the heavy costs of mobilization in liberal democracies do not really matter because the logic of realism can be said to dominate this kind of relationship. To ensure survival, the best way is to defeat and eliminate your enemy, whose behavior is hard to anticipate which provides a consistent threat. That is why the United States set out to ‘root out aggressive fascism and Nazism in Japan and Germany after World War II’ (Russet, 1993: 32).

But things change when two liberal democracies face each other and it is a matter of degree. I have pointed out above that liberal democracies share certain key institutional features. Both sides know how the mechanism of policy-making runs in the opposite side, thus understanding that mobilization of military actions will be costly and time consuming. These decreasing senses of uncertainty and lower information asymmetry have won the time for both sides to think about alternatives. The more liberal democratic the dyad is the more evident the effects are because three institutional features: separation of powers, fair selection of officers and civil society, will emanate stronger powers.

In a more liberal democratic dyad, the system of checks and balances will exert stricter containment on the decision makers, thus having better preventive effects on the abuse of absolute powers. The decision of going to wars or militarized disputes will lead to greater debates in legislature institutions. If those political leaders can not ‘demonstrate a favorable ratio of costs and benefits to be achieved, at acceptable risk’ (Russet, 1993: 38), the decision may be delayed or even be cancelled in a higher possibility.

Equally, the more liberal democratic the dyad is, the more fierce competition of election is because it will be more like a buyers’ market because the voters’ tolerance for the mistakes of government will be lower. To the related officers, they will be cautious or even reluctant to launch military actions in this dyad because if the risky actions prove to be failure, the officers will be more likely to lose the next election campaign. So normally speaking, ‘[w]When states bargain in a crisis, the costs of war generally ensure that there exists some range of settlements that all sides prefer to war’ (Schultz, 1999: 236).The more competitive the democratic elections are in the dyad, the more likely military actions will be not adopted.

For another, more liberal democratic countries will have a more mature civil society. A more mature civil society will have more free media and more advanced NGOs and think tanks. A more free media system, which will increase the transparency of society, becomes a stronger obstacle of acting militarily, which is demonstrated nicely in the following claim: ‘[a]At times of tension, the news consists largely of military moves and statements by political leaders, which give rise to anxiety. But it should not be impossible to reconcile full and truthful reporting with a presentation which reminds readers of the possibility, indeed the necessity, of peaceful solutions to disputes’ (ICSCP, 1980). The prosperity of NGOs and think tanks also matters. More robust NGOs and think tanks will exist in more liberal social environment and means wider participation of citizens in the process of policy making. In a more liberal democratic dyad, both sides of government will have more chances to consult a wider range of policy options from those independent think tanks before actual actions will be taken, and the NGOs, most of which are anti-war ones, such as Oxfam and War Child, will act as the mediators between the two sides, influencing the public opinion through their anti-war propaganda. All these features and activities from a better developed civil society provide higher possibility of alternatives and prolong the process of final decision making, thus rendering a more difficult delivery of militarized actions.

Liberal Norms

The influence of liberal norms coexists with that of democratic institutions. And the influence will be strengthened as the degree of liberal democracy proceeds because the norms will become more prevalent in that case. Liberal norms are evolving. For example, in ancient Athens, political equality and freedom only exist in male citizens, women and slaves were excluded, but after the civil war of United States, slavery was abolished. However, in a dyad of liberal democracy, the influences of liberal norms do not merely mean the evolution of the norms themselves, but also includes the externalization effect and mutual understanding. The former means that liberal democratic countries apply domestic liberal criteria and norms to deal with other democracies. Russet and Maoz (1993: 625) proposed one important aspect in their Normative Assumption1, which are the norms of compromise and non zero-sum game. But other liberal aspects should not be ignored either. Freedom, human rights and justice, these core concepts of liberal democracy have also been externalised. For example, in the 2002 State of the Union Address, Bush justified the claim of “axis of evil” by saying ‘it is both our responsibility and our privilege to fight freedom’s fight’ (Bush, 2002). The more liberal democratic the dyad is, the values and cognitions of respecting human rights, compromising and liberty, will be expressed in the foreign policies to a deeper extent, thus reducing the outbreak of militarized conflicts with higher probability.

The second issue is the mutual understanding in the liberal democratic dyad. The primitive form of this proposition can be found on Kant’s Perpetual Peace, in which he claimed that to achieve perpetual peace, ‘[t]The civil constitution of every state should be republican’ (1988 [1795]: 434) and the citizens of each free states should treat the foreigners with ‘universal hospitality’ (1988 [1795]: 439). The realization of mutual understanding is feasible because those liberal norms reflect the universality of the desire of human beings, such as pursuit for individual freedom and legal rights. I believe that the share in ‘universalistic and tolerant’ (Oven, 1994: 94) liberal norms has created an identity among the citizens in the dyad, which is beyond the national border. The more liberal democratic the dyad is, this identity will become stronger. A stronger identity will more effectively constrain other sentiments which can be vital catalysts to military conflicts, such as nationalism. Nationalism has long been a powerful momentum of launching inter-state military conflicts partly because it creates a parochial identity among people not according to the universal values and preferences shared by all human beings, but to geographical positions, ethnicity or ancient tradition. This narrow identity further creates a difference between “us” and “them”, which provides the legitimacy that ‘justify the goals of the political movement both to the state it opposes and also to powerful external agents, such as foreign states and their public opinions’ (Breuilly, 1996: 167).

However in a more liberal democratic dyad, in which a more liberal and universal identity is accepted and embedded into the mind of people to a deeper extent, which has deepened the degree of “we-feeling”, the former narrow identity’s effect on military actions will be weakened because the legitimacy of conducting hostile behaviors towards the “others” will be reduced consistently. The most prominent example of this will be European Union. Before the establishment of European Union, Europe witnessed the most frequent inter-state wars since the emergence of nation-states. But after its establishment, one can rarely find battles between the democratic European nations. Some key features of European Union, such as the European Parliament and those liberal policies have constructed a supranational identity to some degree. As Fligstein(2008: 139) points out, people will ‘come to see each other less as Italian and French, and thus foreign, and more and more as sharing common interests, a process that eventually will lead to seeing themselves more as Europeans and less as having merely a national identity’. This does not mean that national identity will be replaced by this European identity. In contrast, as Sigalas (2010: 246) mentioned, European identity matters when it is ‘seen as perfectly compatible with the national self-identity’. However, the presence of this supranational identity has constrained the negative nationalistic effect of that identity in national level, and as the EU continues to advance, it will enhance the “we-feeling” in the minds of European. The constraining powers from European identity will be more powerful.


In the above section I have supported the proposition of ‘the more liberal democratic the dyad of states the less likely that dyad is to go to war or have militarized disputes’ by examining it through empirical test and trying to give the theoretical explanations behind the statistics. The result suggests the proposition wins significant statistical support. The underlying theoretical reasons have been divided into two parts from the definition given. I treat both as processes of evolution and during the processes some features contributed to decreasing the possibility of military conflicts will become stronger while the aspects with opposite effects will get weaker.

Although democratic peace has gained various statistical and theoretical support, it can not escape from criticism. Most criticisms focus on the causality mechanism. After all, there may be another more convincing reason superior to DP to explain the peace phenomena. For example, realists may argue that the peace may result from consideration of power politics or national interests rather than democratic structures (Layne, 1994); but the suspect of the causality fails to deny the empirical linkage between peace and democracy, which can not be found in other types of dyad.

Now, we face the reality that we at least know that if we want to achieve perpetual peace, we are in the right situation, as liberal democracy is becoming the mainstream regime type and the number of democratic countries is increasing. But caution should be exercised in this assessment. The validity of the proposition should not be used as an excuse for adopting a foreign policy of forcibly conducting democratization, as the chances of success for this kind of action are highly questionable, as demonstrated in the cases of Iraq and Afghanistan. The best option for those well-established democracies is to preserve themselves, assist those who are already in the process of democratization, and then wait for the ‘realization of Nature’s secret plan’ (Kant, 1988 [1784]: 422) with good will.


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Written by: Wei He
Written at: Bristol University
Written for: Eric Herring
Date Written: January 2011


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