Skip to content

Checking In On Democratic Peace: Part II

The idea that democratic states don’t fight wars with one another isn't as simple as it seems.

Words: Sam Ratner

This analysis was featured in Critical State, a weekly newsletter from Inkstick Media and The World. Subscribe here.

Last week, we looked at new research on the aspects of democratic institutions that contribute to preventing the outbreak of civil war. This week, we’ll return to the core of democratic peace theory: The idea that democratic states don’t fight wars with one another.

In an article in the latest issue of the Journal of Peace Research, political scientists David Altman, Federico Rojas-de-Galarreta, and Francisco Urdinez take on one of the core definitional questions that complicates democratic peace theory. If the idea is that democracies won’t go to war against one another, one of the first things that needs defining is what counts as a democracy. Different researchers have used different definitions, often leading to varying conclusions about the main contention of democratic peace theory.

Altman et al., putting on their quantitative research hats, decided that instead of testing one definition of democracy they should test every definition of democracy. They used data that rated the strength of each state’s democratic institutions on a continuous scale over time to develop a set of over 33,000 dyad years — years in which contiguous states boasted varying levels of democracy and either did or didn’t fight each other.

If the idea is that democracies won’t go to war against one another, one of the first things that needs defining is what counts as a democracy.

The point of all that data was to bring it to bear on the two main hypotheses for the mechanism behind democratic peace theory. The first hypothesis, beloved of Immanuel Kant and other democratic optimists, holds that democracy imposes institutional constraints on states that make it difficult for them to go to war, especially with other democracies. Systems of checks and balances are difficult to navigate on the way to declaring war, the democratic optimists contend, and doubly so when potential adversaries face the same constraints.

The second hypothesis is rather more pessimistic about democracy. To the pessimists, the specifics of democratic institutions don’t matter much at all. Instead, they argue, the observed tendency for democracies not to fight each other is just a subset of a more general rule of international relations: That similar regimes of any type don’t fight each other. These naysayers point out that democracies fight non-democracies all the time, and that autocracies tend not to fight each other.

To Altman et al., these two hypotheses are not completely mutually exclusive. Checks and balances exist in autocracies, they just function differently than in democracies. It may be that the observed peaceful effect of regime similarity is the result of compatible institutions. It may also be the case that the effects of regime similarity are stronger among democracies than among autocracies — that is, that democratic institutions are superior, if not unique, in their capacity to limit conflict.

By plotting all the dyads based on both the mean level of democracy and the democratic spread — that is, how far apart the two countries were on a scale of democracy in that year — the researchers were able to measure the importance of both democratic institutions and similarity in regime type. What they found was good news for the democratic optimists. The higher the mean level of democracy in a dyad, the less chance there was of that dyad going to war. There was also, however, some good news for the democratic pessimists. As other researchers have observed, clear autocracies are also unlikely to go to war with one another.

Yet for dyads in the middle of the democracy scale, where both countries had some democratic and some autocratic characteristics, regime similarity didn’t seem to do much to prevent conflict. Simply having similar democracy scores doesn’t on its own prevent conflict between two states.

By measuring democracy on a continuous scale rather than as a binary designation, Altman et al.’s work lends credence to the idea that regime structures matter in determining the outcomes of international disputes. Strongly democratic dyads do seem to have an advantage over strongly autocratic dyads in preventing conflict, but perhaps the key is that each regime’s decision-making apparatus must be legible to the other to gain the benefits of the so-called democratic peace.

Sam Ratner


Sam Ratner is a contributing editor at Zitamar News, where he covers southeast African security issues, and a founding editor of Fellow Travelers Blog. He earned his MPA in international security policy from Columbia University's School of International and Public Affairs. He tweets at @samratner.


Hey there!

You made it to the bottom of the page! That means you must like what we do. In that case, can we ask for your help? Inkstick is changing the face of foreign policy, but we can’t do it without you. If our content is something that you’ve come to rely on, please make a tax-deductible donation today. Even $5 or $10 a month makes a huge difference. Together, we can tell the stories that need to be told.