The Democratic Peace Theory

Why democracies do not go to war with each other and why this matters

Disclaimer: I wrote this for another blog of mine out on the wastelands on the internet a year ago. I simply refined it for this post because I think this theory deserves more attention. I want to motivate myself to write something similar about Just War Theory. Future posts will not be nearly as long or as detailed.

Introduction

The Democratic Peace Theory (DPT) is a hugely popular and highly influential theory in International Relations. It is the closest International Relations (IR) has come to a law-like rule. Usually the humanities, especially political science, avoids very strong claims. Put simply, the theory says that democratic states never, or rarely, wage war with one another. Although there are some that have questioned the statistics (see Arguments against), the major disputes lies not in the fact that democracies do not go to war, but in why they don’t. Realists of course emphasise power, whereas liberals (and social constructivists) emphasize democratic constraints and democratic norms. 

Keep in mind in IR realists basically emphasize power, military and economic might, and self-interest. Liberals are not modern leftists. In IR liberalism simply emphasizes the importance of democracy, individual rights, and the importance of free trade (you could still be pro-government intervention in the economy or against it and be a liberal in the IR sense). Constructivists in turn highlight the social values of states, like human rights, and how states actually believe in them.

The Democratic Peace Theory became popular in the 80s when scholars noticed a correlation between democratic states and peace between them. This spawned an intense but extremely interesting debate. 

Definition of democracy and Immanuel Kant

In order to understand the debate it is necessary to know what DPT scholars mean with “democracy”. DPT scholars draw their main inspiration from Immanuel Kant. In 1795 Kant wrote about a "Perpetual Peace" (I have not read it so I draw the following from other sources). He believed that a liberal pacific union will expand over time, leading to an eventual worldwide peace. This peace is guaranteed by three articles:

Article 1: A state must be republican. This means it manages to combine moral autonomy, juridical quality, a separation between the executive and legislature, and individualism and social order. It allows for private property and a market-oriented economy. In other words, it is an actual democracy that respects free trade.

Article 2: These republican states establish a pacific union among themselves, which eventually expands (with setbacks) across the world. This is not a world-government - these states simply become part in this union of their own will without some overarching authority. Outside of this union liberal governments (and non-liberal ones) are still in an anarchic state of war with each other. The EU is probably the closest idea that Article 2 has in mind, though as far as I know a central political authority is not the point. The EU is an example in the amount of cooperation between European nations.

Article 3: Republican states should treat foreigners with hospitality, including allowing them to trade with republican states. This provides a material incentive whereby peoples and states prefer peace (and trade) to war.

In short, peace is attained if states hold to liberal-democratic values, if they are part of a union populated by democracies, and if they have high degrees of (economic) interdependence.

Some scholars do however question whether Kant's philosophy has been interpreted correctly by DPT proponents. Caranti (2016) claims that a state being a republic is more about the ideals of citizens and state leaders than about the actual structure of the state. In this sense, a monarchy or oligarchy can be a “republic” in so far as the leaders actually see themselves as representatives of the entirety of its people and act in the entire public's true interests. In contrast, it is possible for a democracy not to be a “republic” if its leaders only represent either themselves or some subsection of society. This being said, most DPT scholars do not agree with Caranti's view of Kant's philosophy. But keep in mind that everything is debatable.

In addition to what Kant argued, DPT scholars also add that in a republic the public should have leverage over war decisions, and that they should have competitive elections and free speech. 

Arguments in favour

The argument in favour of the DPT is mainly presented by liberals, with some support from social constructivists. A number of quantitative studies have analysed the amount of wars between states over the last few centuries to determine the amount of times that democracies have gone to war. Initially liberals argued that this amount was zero - they said that democracies never go to war with each other. Over time, however, the argument has become more modest: democracies rarely go to war with one another. This qualification is important as it makes the theory more powerful.

There are a number of explanations given to explain how democracy leads to peace. The two most important factors are institutional constraints and norms.

Institutional constraints

Liberals argue that democratic states have a separation of power. Executives (such as the president) share their power with ministers, parliaments, and to some extent the media. This is coupled with a free press and opposition parties opposing government policies. This significantly decentralizes power from the president.

Because of all of this, the ruling elites have to listen to the public if they want to be re-elected. If they do not, then they are ousted from their positions. Similarly, such elites have to convince the public to support wars. It is not easy for a president to simply force its people into a war. He could do this, but such a war would be unpopular if the public does not support it, which means he might be ousted from power.

The public, in turn, is sceptical of going to war. The country has to spend money that could rather be spent domestically and the public, rather than the elite, will be the ones who will have to die for these conflicts.

The democratic elite therefore rarely goes to war with another state against the wishes of the public. Democratic leaders also know that their fellow democratic allies are constrained in a similar way, and hence they do not feel as insecure towards fellow democracies as they do towards authoritarian states. 

Basically, Angela Merkel is constrained by the media, the opposition, coalitions, etc. But she knows that Macron is also constrained by the media, the opposition, coalitions and the others. This makes Merkel less afraid of a possible French invasion. And of course it makes Macron less afraid of a German invasion.

In contrast, both Macron and Merkel knows that Erdogan is not so constrained. He has a lot of power, has dominance over his enemies and the media, and Turkey is not so dependent on Germany and France. The lack of a free press and checks and balances in Turkey means that the possibility of war with Turkey is more likely as Erdogan has less hurdles to overcome to start a war. So what makes France and Germany feel safe about each other, does not apply to Turkey.

Normative constraints

The second major factor of democracies that lead to peace towards one another are democratic norms. This is a more constructivist take and therefore requires an explanation. Norms are shared beliefs that states actually believe in. You simply do not prevent women from voting. You simply do not nuke another state. You simply do respect free speech, pacifism, and mediation. These norms are sometimes codified into law (such as in human rights resolution), but sometimes they are simply assumed. These beliefs are more social than political, but they do affect the political.

With the above in mind, liberal democratic norms ensure peace between two democratic states in two ways. Firstly, democratic norms mean the public inherently support peaceful resolutions, political competition, openness, a free media, and trade. Studies show that democratic individuals associate other democratic states as allies by default. There is a tendency to associate other democracies as inherently trustworthy (see the sources cited below which provide convincing proof of this).

However, democratic states know that undemocratic states will exploit these democratic norms. They will thus shift norms when confronted by nondemocratic rivals. In this case a democratic state is forced to conduct relations by the normal norms of international relations. Consider how suspicious Britain and America is about Russia and China abusing the former’s openness by interfering in their elections. Britain does not think America is interfering in its elections, but they do think that of Russia.

Democracies share liberal norms with other democracies, but not with non-democracies. This explains why democratic states are not also peaceful and cooperative with nondemocratic states.

The second way in which democratic norms ensure peace is by democracies externalising these norms. This basically means that, similar to the institutional factor, democratic states know other democratic states hold to the same norms. Germans know that Spaniards also believe in democracy, pacifism, and pluralism. In contrast, Iran does not have the same liberal norms of free speech, women’s rights, and others.

It would be easier for Merkel to convince her public to invade Iran than it would be to convince them to invade Spain.

The Evidence and Cases in favour

Quantitative studies have been done to support the contention that democratic states are less likely to escalate disputes among each other (Maoz and Russet 1993). These studies have tested for both norms and institutional constraints. Power relationships do make a difference, as realists would predict, but democracy nonetheless remains a strong and independent actor. The Cold War and American dominance do also help peace, but democracy is an independent factor as well. As Maoz and Russett (1993 633) put it: "The phenomenon of democratic peace is real, not spurious". Even more, Poznansky and Scroggs' (2016) quantitative study show that democracies are also less likely to threaten each other with force. On a normative view, another study (Jakobsen, Jakobsen & Ekevold 2016) shows that democracies do lead to more peaceful citizens. Democratic citizens tend to be more pacifist thatn non-democratic citizens. In short, democratic states are more peaceful towards one another. 

Arguments against

Frequency

The critiques against the DPT has been made mostly by realists. One critique, which seems to be held less in recent scholarship, is that the statistics which favour DPT are inconsequential; there have not been many democratic states in the past and therefore the chances of war at any point in time is itself low. Even in the time where there have been many democracies (such as the 20th century) the world was dominated by first the Cold War and then American hegemony. As such, if there is a correlation between democracy and peace it is not of great significance. It could be pure chance, or due to America and Russia maintaining order over their areas of influence. 

Counter-examples

Realists point out a number of conflicts between democracies. These include the War of 1812, the Anglo-Boer War, the Spanish-American War, the First World War (Germany was just as democratic as Britain) and even the Second World War (democratic Finland initially allied with Germany). In many of these cases the citizens of one or both democracies were in favour of war and, in the case of the Spanish-American War, actively forced their leaders into war against their leaders' judgment. The critique even goes to ancient times where democratic Athens and Syracuse went to war.

Institutions and norms

Institutions

Realists also target the two main factors. On the institutional level, they point out that even if this logic holds, it doesn't explain why democracies are still violent against non-democracies. The same institutions and peace-minded citizens of democratic states should make them just as wary of war against non-democratic states. A war between America and Iraq, for instance, also has to go through checks and balances, America citizens have to pay the moral and physical price, etc. The institutional logic therefore does not explain what is unique about non-democracies vs democracies. 

Also, it is not obvious that democratic leaders are more accountable to their citizens than non-democratic leaders. According to Rosato (2003) autocrats have been more likely to lose office or be punished if they were involved in a costly war. The consequences for Gadhafi or Saddam Hussein to lose a war is much higher than than if Trump or Boris Johnson loses a war, as the fate of the former two show. (Compare the fate of Hussein and the fate of Tony Blaire, or of Hillary Clinton and Gadhafi).

The public is also not necessarily motivated by arguments of cost. Those who die in war are usually people who voluntarily joined the army, with their friends and family aware of the risks. As such, the public may be more permissive towards conflict than proponents of the theory would argue. This is worsened by the real phenomenon of publics "rallying around the flag" when a country is forced to go to war. People become patriotic when a war starts and at least initially supports retaliation.

Norms

The normative element has also been critiqued. There have been cases where democracies have come close to war with fellow democracies. Examples include the Fashoda crisis between Britain and France in 1989, Britain nearly going to war with the America during the American Civil War (the Trent affair), the Venezuela boundary dispute between the US and Britain again in 1895-96, and the Ruhr crisis in 1923 between France and Germany. 

In each case it was realistic considerations of the balance of power which made these democratic states favour peace, not democracy (Layne 1994). For instance, the USA could not realistically fight both Britain and the Confederacy during the Civil War and therefore opted to appease Britain. They were driven by logical self-interest, not by a respect for Britain being a democracy. Similarly, in the dispute over Venezuela, Britain appeased America because it did not want to antagonise America while Germany was growing in power in Europe. 

The normative element also does not explain why established democracies have undermined new democracies through covert actions or limited military manoeuvres . Consider how America has spied on its allies and toppled democratic third-world states. Indeed, Crandall et al. (2018) show that democracies are more willing to take covert action towards other democracies - including sending democratic suspects to black sites without trail. It is precisely because violent action against democratic citizens is considered immoral that democratic states will attempt hide it. Ironically this leads to worse democracies treating suspects of other democracies worse than they treat suspects of authoritarian states. An institutional logic still allows for this, but not a normative one. 

Aside from the above, the colonial and imperial conflicts over the 19th and 20th centuries show that liberal democrat states have waged war for non-liberal reasons. The way these wars were fought, including establishing concentration camps during the Boer war, makes it doubtful whether these states were motivated by liberal norms.

Definitions

Critics further accuse DPT scholars of changing the definition of "democracy" in a way that it loses its meaning. (Layne (2001: 801-802) especially makes a powerful critique of this). For instance, the Anglo-Boer War is not seen as a war between democracies by DPT scholars. The Boer republics are not considered democratic by some them scholars because these states did not allow women and black people to vote. However, DPT scholars still consider America and Britain democracies at the same time even though they also did not allow either to vote. In fact, if a population is willing to oppress minorities, why would they be unwilling to oppress foreigners?

The same dual standards apply to the case of Germany and the UK before WW1. Both had similar domestic liberties. Germany also had a representative legislature, competitive elections, and open public debate. Although the Kaiser had significant autonomy on foreign affairs, the same was true of British and American executives. Yet DPT scholars don’t consider Weimar Germany to have been a democracy.

Finland in particular is important depending on the definition of democracy. Finland was an ally of NAZI Germany in opposition to the Soviets. Some DPT scholars only count wars where more 1000 troops were involved or 100 casualties were suffered. If this is acceptable, then Finland's participation in WW2 does not count. DPT argue add that Britain had to be convinced by Stalin to declare war on Finland, that Finland took no hostile action against Western countries, and that the target of a Western operation against Finland was a German-operated nickel mine. However, even though DPT scholars exclude Finland on these qualifications, they still include Belgium's participation in the Korean conflict, which had less than 25 casualties a year. Some realists consider Finland's exclusion to be an ad-hoc response

Liberal Rebuttals

Frequency

Proponents of DPT have defended the theory against the above critiques. On the significance of the correlation between democracy and peace, liberals have presented a number of quantitative studies which have shown such a correlation. In these studies they accounted for power-realities, economic interdependence, proximity (border states are more likely to go to war with each other), development, and a number of other factors. They usually point out that although there may be correlations between some other factors and peace (for example, realist power concerns), democracy is nonetheless an independent factor in favour of peace. Put simply, American and Soviet hegemony in a bipolar world did help peace between democracies, but this is an additional factor. Not the primary one.  

Institutions and norms

On institutional constraints, liberals point out that the institutional and normative elements go hand in hand (see especially Risse (1995) for the importance of norms in addition to institutions). Democracies constrain the executive, and allow the democratic norms to have an effect. If we only consider institutional constraints, then one could argue that less constrained democracies would exploit more constrained democracies. Conversely, if the public holds to democratic norms but the state is ruled by a repressive dictator, then those norms will fail to be expressed towards democracies. In contrast, taken together, a constrained executive accountable to its citizenry allows democratic norms to be expressed towards fellow democracies.

As an example, a “democratic” Iraq where people still do not respect basic democratic ideals would not be conducive to a democratic peace. Conversely, if America becomes a dictatorship, the democratic norms of the American people will not have an effect on America’s foreign policy. Both the norms and the institutions are needed. America has to be both a democracy and consist of people that hold to democratic norms.

Lastly, supposed counter-examples showing war between democracies have been answered in a number of ways. It might take time for new democracies to accept these norms. An oppressive South Africa that becomes a democracy in 1994, might still be more willing to wage war in 1996 against Botswana than in 2021, simply because it takes time for these new pacifist norms to become widespread. Scholars such as Weart (2001) argue that four years should be sufficient for a liberal political culture to develop. 

Perceptions

An interesting line of argument to accommodate counter-examples focuses on perceptions. Owen (1994) (as well as Risse (1995)) especially advanced this view. Such an approach points out that America in 1812 did not consider Britain to be a democracy. They viewed Britain as a monarchy rather than a "republic". America believed Britain always tried to crush freedom around the world. Britain, similarly, initially did not consider America a democracy during the Civil War.

However, when Lincoln made a proclamation against slavery the British public’s opinion changed. They began to side against the Confederacy and with the States. As such, realist factors might account for the two states avoiding war during the Civil War due to power realities as at that point Britain did not consider America to be a liberal state. But once Britain realised America was democratic, the public opted against war even though a divided America would have been in Britain's interest. Some DPT scholars also point out that realism, as opposed to the DPT, fails to explain why Britain chose to side with America in the first place, rather than accommodating Germany instead. From a realist view America was also becoming a serious international rival. That Britain chose to appease the States rather than the Germans proves the point that democracy matters. 

In a similar vein, in the advent to the First World War, Britain and France did not consider Germany to be democratic even if Germany was a democracy. Past conflicts and the predominance of the Kaiser in German politics argued against such a perception. As we would expect, the same holds to true to ancient Greece. Syracuse did not consider Athens to be a democracy.

Additionally, scholars also argue that it might be a specific feature of modern representative democracy (rather than Athens' direct democracy) that encourages peace. In contrast to direct democracies, in modern systems state leaders exist can be voted out of office. In direct democracies the citizens themselves cannot be punished for mistakes as every decision is taken collectively.

Lastly, the issue of manipulating the definition of "democracy" goes both ways. DPT scholars give their different definitions of democracy precisely so they can be clear on what they mean. In contrast, critics are also subject to bias by reinterpreting the definition of "democracy" in a way to oppose the DPT.

Realist responses and liberal counter-responses

The debate over the democratic peace theory has not subsided. For every response by proponents, there have been critiques by realists.

Correlation

On the question of correlation, to my understanding realists have come to accept that there is at least a strong correlation between democracy and peace. However, they do not think democracies never go to war with each other and they strongly question the causal factors between democracy and peace. As such, they argue that power-realities (as mentioned) or some other third factor adequately explains both democracy and peace (see below). 

Perceptions

Realists have also targeted the idea of perceptions on two fronts. Firstly, it is difficult to measure perceptions. We cannot know exactly what policy-makers had in mind and what they perceived. Even where we do know, it is still difficult: Do we take into account opposition parties? The media? Factions in government? If so, to what extent? If a government favoured a war, but the opposition party opposed it based on the opposition party's view of the enemy, is the perception in favour of the war or not? 

This can lead to a tendency towards bias. Cases where democracies did fight each other can be defended by saying opposition parties perceived the other state as non-democratic, or vice versa. Even worse, if perceptions are divorced from objective realities, then there is a risk that elites or others can manipulate the public into thinking that other democratic states are enemies. Indeed, the US has supported covert operations against other democracies, such as in Iran in 1953. 

However, in anticipation of this critique, Owen (1994) showed liberals do have stable conceptions of what democracies look like. During times of crises with other liberal states, the public do not suddenly change their opinions of their potential foes. For example, if there is a crisis between Britain and Germany, Britains do not suddenly begin to think that Germany is undemocratic. This shows that a state simply being an enemy does not necessarily deceive liberals into thinking it is illiberal.

Theory: Liberalism and Realism (and social constructivism)

The DPT goes to the heart of the debate between liberalism and realism. If the DPT is true, then liberalism is greatly enhanced: individuals are paramount. Anarchy can be overcome in favour of peace. A state's behaviour is driven by domestic factors. In contrast, realism - if it manages to defeat the theory - had opportunities to show the predominance of self-interest, the balance of power, and anarchy in determining state behaviour. Constructivism in turn would also be somewhat vindicated if the normative aspect of the DPT holds. If it does, then norms are shown to matter. States are not only motivated by power, but also by values, beliefs and ideas. In this case liberalism and democracy.

However, there are also problems. Viewing the theory only through theoretical lenses might lead to a stale-mate. Liberalism gives the individual, and a publicly accountable state, primacy over international factors. Yet the role of the "pacific union" in containing state behaviour is not addressed. By emphasizing the freedom of states to behave contrary to power realities, it does not focus on how the democratic peace can structurally alter the behaviour of democratic nations. To what extent can this union prevent democratic states from backsliding? Or perhaps even encourage it? To what extent does a state's awareness of power - which many DPT scholars believe at least have some influence, manage to affect democracies' actions?

In other words, suppose there is a democratic peace right now among European states. What prevents Poland from backsliding? Why is Poland backsliding? It is part of the EU, has democratic norms, etc. This “union” of democratic peace does not do anything and in fact it is surprising that democratic states in this “union” would change. At best you could point to the EU taking Poland to the EU Court. But this supra-national government is not part of DPT. It should not be necessary to have such a powerful political organization to keep peace between democracies.

This is concerning as it means that even if DPT is true, it doesn’t mean that democracies won’t become illiberal in the future. Even more, it also means that democracies that become autocracies could eventually wage war with their former allies. America might be a democracy now, but it may not be one tomorrow. And that should concern the Italians.

In short, it is worth keeping in mind how the DPT is situated within IR's theoretical debates and what it would mean if one of these theories are vindicated. If DPT is true, then we can be more optimistic about an elightened future of democratic states. If it is false, well then there is less optimism.

Practical concerns

The democratic peace theory also has practical application outside of academia. The idea that democratic states do not wage war with each other has had an important influence on (American) foreign policy. Bill Clinton, George Bush, and many of their predecessors, have held to this idea. If democracies do not go to war, so America argues, then American security requires the spread of democracy. The best way, the reasoning goes, to make Iran or China allies is to turn them into democracies. Woodrow Wilson and others had similar ideas in the aftermath of the First and Second World Wars. This is seen in the forced and successful democratization of Japan and Germany.

However, the potential for misuse is obvious. The American invasion of Iraq is a case in point. Wanting to spread democracy to ensure American security, they destabilized an entire country, radicalized its inhabitants, and created insecurity for both the region and the US itself. 

Additionally, if perception matters, then it is also not enough to establish a democratic state. That state needs to view other democracies as democracies. Forcibly spreading democracy may therefore lead to the opposite result as, even if successful, those inhabitants might view the imposing democracy as imperialistic rather than as a liberal, pacifist nation. Consider how America was somewhat successful in making Iraq a democracy. That does not change the fact that because of this both Iraqis and citizens around the world no longer consider America to be a true democracy.

China is an interesting example. The US encouraged China to open up its economy in the 1990s. It was believed that trading with China, encouraging China to partake in (mostly liberal) international institutions such as the UN and WHO, and generally making China dependent on these institutions would all make China more democratic and, because of that, more peaceful towards the West. Recent years, however, have shown that this approach has been naive. China has become more authoritarian. DPT thinking arguably worsened the situation.

None the less, there is room for hope. Encouraging democracy does help peace. America and Japan turned into powerful American allies after becoming forcibly democratized. South Africa, South Korea, Russia (before Putin) and others have become more peaceful towards other states after their democratization.

At the very least, keep in mind that DPT is a theory and not a well worked-out foreign policiy.

Future possibilities

Is this everything there is to know about this debate? No. There are interesting alternatives.

As mentioned, certain realists believe there might be a third factor which causes both democracy and peace between them. They usually focus on power or capabilities as that factor. However, in recent years other potential theories have come about. I only came across these alternatives in the last article I read (Ungerer 2012) before writing this post.

One possibility is to turn the relation between democracy and peace upside down. Instead of democracy leading to peace, it might be the case that peace leads to democracy. States in violent neighbourhoods need larger armies and better tax systems. Such states subsequently centralize power to increase taxes and keep control over their larger armies. In other words, insecure states will tend to be less democratic as power is shared among less people. Conversely, when peace is achieved the army is diminished and civil society, parliament and other actors are allowed more power. Peace, then, leads to gradual democratization.

Another possibility is that a third factor explains the correlation of both democracy and peace. This is the "economic norms" explanation. Basically, it argues that a successful economy requires both peace and democracy. The two are thus the result of a capitalist economy, rather than peace causing democracy or vice versa. Democracy ensures equality between citizens and respect for private property which is necessary for growth. Trade is hampered if certain individuals get preferential economic opportunities. Liberal democratic values then originate not from democracy per se, but rather from the market economy.

Conclusion

The democratic peace theory is highly debated. There seems to be an acceptance that there is at least a correlation between democracies and peace. The debate lies within the reasons for this. Is it because of norms and institutions? Or is it because of realistic considerations of power capabilities? Or is it perhaps due to some unknown third factor, such as the economy?

For every critique there is a justification which is just as convincing. For every counter-example there is a reinterpretation. This makes it difficult to pin down who exactly is right. The practical consequences of the DPT for the world is significant. If true, then democracy should be spread. If not, then believing it is true can hamper a state's security.

Theoretically it also has high stakes for the main IR theories. Is anarchy paramount? Or can states overcome it? 

All these questions make the democratic peace theory important and interesting. It is a worthy area to research.

For my own part, I think the DPT is mostly true. Democracies avoid wars with each other not only because of power, but simply because of these constraints and values. Nonetheless nothing in IR is absolute. The exceptions like the Boer War is hard to explain. And there are some curious problems left to explain. Power should also not be ignored - it was foolish to let China become so poweful. Nonetheles, if accepted cautiously, the DPT is useful in understanding state behaviour and in formulating your own foreign policy.

Bibliography

Caranti, L. 2016. Kantian peace and the liberal peace: Three concerns. The Journal of Political Philosophy, 24(4): 446-469. On the proper use of Kant's philosophy

Coetzee, E. & Hudson, H. 2012. Democratic peace theory and the realist-liberal dichotomy: The promise of neoclassical realism? Politikon, 39(2): 257-277.

Crandall, C., Cox, O., Beasley, R. & Omelicheva, M. 2018. Covert operations, wars, detainee destinations and the psychology of democratic peace. Journal of Conflict Resolution, 62(5): 929-956. Details covert actions taken by America against fellow democracies

Doyle, M. W. 1983a. Kant, liberal legacies, and foreign affairs. Philosophy & Public Affairs, 12(3): 205-235. An important early work on the DPT

Doyle, M. W. 1983b. Kant, liberal legacies, and foreign affairs, Part 2. Philosophy & Public Affairs, 12(4): 323-353.

Elman, C. 2001. Introduction: History, theory and the democratic peace. The International History Review, 23(4): 757-766. The beginning of six articles, all of them cited here. All six are worth the read.

Elman, M. F. 2001. Falsification, generalization, and the democratic peace.  The International History Review, 23(4): 814-823.

Heraclides, A. & Dialla, A. 2015. Intervention and non-intervention in international political theory. In Humanitarian Intervention in the Long Nineteenth Century, edited by A. Heraclides & A Dialla. Manchester: Manchester University Press. For the discussion on Kant's view of humanitarian intervention.

Jakobsen, J., Jakobsen, T. G. & Ekevold, E. R. Democratic peace and the norms of the public: A multilevel analysis of the relationship between regime type and citizens' bellicosity, 1981-2008. Review of International Studies, 42(5): 968-991

Layne, C. 1994. Kant or cant: The myth of the democratic peace. International Security, 19(2): 5-49. Highlights cases where realpolitik prevented war between democracies rather than norms or institutions

Layne, C. 2001. Shell games, shallow gains, and the democratic peace.  The International History Review, 23(4): 799-813.

Maoz, Z. & Russett, B. 1993. Normative and structural causes of democratic peace, 1946-1986. The American Political Science Review, 87(3): 624-638. A quantitative study

Owen, J. M. 1994. How liberalism produces democratic peace. International Security, 19(2): 87-125. Perceptions

Ray, J. L. 2001. Democracy and peace: Then and now.  The International History Review, 23(4): 784-798.

Risse, T. 1995. Democratic peace - warlike democracies? A social constructivist interpretation of the liberal argument. European Journal of International Relations, 1(4): 491–517. A social constructivist perspective

Rosato, S. 2003. The flawed logic of democratic peace theory. The American Political Science Review, 97(4): 585-602.

Rosato, S. 2005. Explaining the democratic peace. The American Political Science Review, 99(3): 467-472.

Poznansky, M. & Scroggs, M. K. 2016. Ballots and blackmail: Coercive diplomacy and the democratic peace. International Studies Quarterly, 60(4): 731-741.

Russet, B., Layne, C., Spire, D. E. & Doyle, M. W. 1995. The democratic peace. International Security, 19(4): 164-184. An interesting article featuring both proponents and critics

Solingen, E. 2001. Domestic coalitional analysis and the democratic peace. The International History Review, 23(4): 776-783.

Ungerer, J. L. 2012. Assessing the progress of the democratic peace research program. International Studies Review, 14(1): 1-31.

Weart, S. R. 2001. Peace among republics. The International History Review, 23(4): 767-775.