Why They Don’t Fight

Few hypotheses in international relations are more influential than democratic peace theory—the idea that democracies do not go to war with one another. The idea, the political scientist Jack Levy wrote, “comes as close as anything we have to an empirical law in international relations.” It has motivated U.S. foreign policy for nearly a century. In the early 1900s, U.S. President Woodrow Wilson embraced democracy promotion as a means to peace. During the Cold War, successive administrations spoke of the standoff with the Soviet bloc using grand ideological terminology. No distillation was grander than President Ronald Reagan’s address before the British Parliament in 1982, in which he claimed that the West exercised “consistent restraint and peaceful intentions” and then proceeded (seemingly without irony) to call for a “campaign for democracy” and a “crusade for freedom” around the world.

Democratic peace theory became especially influential once the Cold War ended, leaving the United States truly ascendant. In his 1994 State of the Union address, President Bill Clinton claimed that “the best strategy to ensure our security and to build a durable peace is to support the advance of democracy elsewhere.” His administration then surged aid to nascent post-Soviet democracies. Clinton’s successor, George W. Bush, was equally vocal about the need to advance liberalism in order to promote peace, telling the 2004 Republican National Convention, “As freedom advances, heart by heart, and nation by nation, America will be more secure and the world more peaceful.” As president, Bush even used democratic peace theory as one of the justifications for invading Iraq. In a speech on the war in November 2003, he declared, “The advance of freedom leads to peace.”

The idea that democracy breeds peace, however, is at best half true. The United States has repeatedly attacked other countries. Europe’s major democracies also have a long history of intervening in other regions, such as the Sahel. And rather than marking the permanent triumph of liberal democracy, the post–Cold War period is now defined by growing divisions and conflict. As is now plain, the spread of liberalism does not by itself curtail fighting.

Yet the proliferation of wars carried out by democracies does not disprove democratic peace theory wholesale. Liberal states may not act peaceably toward everyone, but they act peaceably toward one another. There are no clear-cut cases of one democracy going to war against another, nor do any seem forthcoming. In fact, the global divisions emerging today confirm democratic peace theory: once again, the line runs between liberal states and authoritarian ones, with the United States and its mostly democratic allies on one side and autocracies, most notably China and Russia, on the other. The world, then, could be peaceful if all states became liberal democracies. But until that happens, the world will likely remain mired in a dangerous ideological standoff.

GREAT MINDS

Democratic peace theory has a long history. In 1776, the American revolutionary Thomas Paine argued that liberal states do not fight one another, writing that “the Republics of Europe are all (and we may say always) in peace.” When Paine’s country gained independence and then drafted its constitution, the document implicitly referred to the idea that democracies should be conflict-averse. It placed the authority to declare war in the legislature—the branch with members directly elected by the public—in part to prevent the country from entering unpopular conflicts.

Democratic peace theory had early proponents across the Atlantic, as well. Its most influential initial champion was the German philosopher Immanuel Kant. In 1795, Kant published Perpetual Peace, an essay that took the form of a hypothetical peace treaty and that established the concept’s theoretical foundations. Representative republics, Kant explained, did not fight one another for a mix of institutional, ideological, and economic reasons.

Kant’s writings called for states to adopt a representative republican form of government with an elected legislative body and a separation of powers among the executive, judiciary, and legislative branches—all guaranteed by constitutional law. Kant’s republic was far from a modern democracy; only male property holders could vote and become what he called “active citizens.” Nonetheless, he argued that elected representation would inspire caution and that the separation of powers would produce careful deliberation. Although these forces would not guarantee peace, he admitted, they would select for rational and popular conflicts. If “the consent of the citizens is required to decide whether or not war is to be declared,” Kant wrote, “it is very natural that they will have great hesitation in embarking on so dangerous an enterprise.” For doing so, he continued,

would mean calling down on themselves all the miseries of war, such as doing the fighting themselves, supplying the costs of the war from their own resources, painfully making good the ensuing devastation, and, as the crowning evil, having to take upon themselves a burden of debt which will embitter peace itself and which can never be paid off on account of the constant threat of new wars. But under a constitution in which the subject is not a citizen, and which is therefore not republican, it is the simplest thing in the world to go to war. For the head of state is not a fellow citizen, but the owner of the state, and a war will not force him to make the slightest sacrifice so far as his banquets, hunts, pleasure palaces and court festivals are concerned. He can thus decide on war, without any significant reason, as a kind of amusement, and unconcernedly leave it to the diplomatic corps (who are always ready for such purposes) to justify the war for the sake of propriety.

Kant also called for republics to make commitments to peace and universal hospitality. The former idea entailed a commitment to peaceful relations and collective self-defense, rather like NATO’s. The latter meant treating all international visitors without hostility, offering asylum to people whose lives were at risk, and allowing visitors to share their ideas and propose commercial exchanges. This combination, Kant said, would build security, create mutual respect, and generate economic ties that lead to tranquility. And thus, republic by emerging republic, the combination would create peace.

Democratic peace theory had early proponents on both sides of the Atlantic.

Kant did not argue that his ideas would stop tension and conflict between republics and autocracies. In fact, he argued that representative republics might become suspicious of states not ruled by their citizens. But he did believe that liberal values such as human rights and respect for property would curb a country’s desire for glory, fear of conquest, and need to plunder—three forces that drive states to war. He therefore thought that liberal republics would be respectful and restrained when addressing one another, even as they remained suspicious and fearful of nonrepublics.

Views similar to Kant’s on liberty, republics, commerce, and peace spread throughout nineteenth-century Europe and beyond. French Foreign Minister Francois Guizot, a conservative liberal who served from 1840 to 1848, spoke enthusiastically about mutual freedom as a foundation for an entente with the United Kingdom. British Prime Minister William Gladstone, who led his country for much of the latter half of the 1800s, was a proponent. And when U.S. President Abraham Lincoln issued the Emancipation Proclamation in 1863, it helped tilt liberal opinion in Europe toward the Union and away from the Confederacy.

It was not, however, until World War I that the full democratic peace proposition became central to foreign policy. Wilson’s war message in April 1917—in which he declared that the battle between autocracies and democracies would establish “the principles of peace and justice”—was the clarion call. The clash between democracy and autocracy continued to shape policy as the decades went on. The behavior of the United States during the Cold War, for example, was often motivated by a belief that spreading liberal values would yield peace. As Secretary of State John Foster Dulles declared in his 1953 Senate confirmation hearing, “We shall never have a secure peace or a happy world so long as Soviet communism dominates one-third of all the peoples that there are.” President John F. Kennedy echoed that theme in his 1963 speech in West Berlin, declaring that “when all are free, then we can look forward to that day when this city will be joined as one and this country and this great Continent of Europe in a peaceful and hopeful globe.”

But that same month, in a powerful address at American University, Kennedy warned of the complementary dangers of ideological confrontation with the Soviet Union. “Let us not be blind to our differences—but let us also direct attention to our common interests and the means by which those differences can be resolved,” he said. “If we cannot end now our differences, at least we can help make the world safe for diversity.”

TIME AFTER TIME

As liberalism endured and spread, intellectuals began empirically testing whether democratic peace theory actually held true. In 1939, the American journalist Clarence Streit published a qualitative historical analysis to see whether liberal democracies tended to maintain peace among themselves. Discerning that the answer was yes, he proposed that the decade’s leading democracies form a federal union, which would help protect them from fascist powers. In 1972, Dean Babst, building on Quincy Wright’s magisterial A Study of War from 30 years earlier, carried out a statistical analysis that also suggested a correlation between democracy and peace. In 1976, Melvin Small and J. David Singer confirmed this finding but demonstrated that democratic peace was limited to relations between democracies. Republics, they showed, were still prone to fight autocratic regimes.

In the decades since, international relations scholars have continued to study the democratic peace paradigm. They have shown that the relationship between democracy and peace is statistically significant even when controlling for proximity, wealth, and trade. They have determined that the theory holds even when states attempt to constrain each other.

Academics have advanced a wide variety of explanations for why the concept is so sturdy. Some have argued that part of the reason lies in the disproportionate influence that international institutions have with liberal countries. Research shows that democracies tend to delegate a lot of policymaking to complex multilateral bodies, such as the European Union and the World Trade Organization, in part because their leaders can use these groups to entrench policies before cycling out of office. Other scholars have argued that liberal norms favoring peace, human rights, and respect for fellow democracies hold sway over policymakers and publics. And still others have pointed to the benefits of trade and economic interdependence associated with relations among capitalist democracies. States that frequently trade, after all, will lose wealth if they fight one another.

Still, democratic peace theory has attracted plenty of critics. Henry Farber and Joanne Gowa have pointed out that there are other forces at work in stopping wars between democracies. During the Cold War, for example, NATO’s need to protect itself from the Soviet bloc ensured that Western Europe cooperated—although the region’s post–Cold War peace suggests more than collaborative containment is at work. Other scholars have pointed out that none of the factors used to explain democratic peace theory can stop war on its own. States that are deeply involved in international institutions, after all, do launch invasions. Peaceful norms and ideas work only if democracies heed them in the policymaking process, yet they are often ignored. The shared decision-making powers of republics should encourage deliberation, but the division of powers and rotation of elites can also lead democracies to send mixed signals, putting other states on edge.

And economic benefits can be achieved through plunder, not just through trade. Powerful democratic states can have rational incentives to exploit wealthy, weak democracies, especially if the latter are endowed with natural resources or strategic assets such as shipping lanes. Rational material interest is not enough to explain why xenophobic democracies have not tried to conquer democracies of other ethnic groups.

But put all the explanatory factors together, and democratic peace theory coheres. When governments are constrained by international institutions, when political elites or the electorate are committed to norms of liberty, when the public’s views are reflected through representative institutions, and when democracies trade and invest in one another, conflicts among republics are peacefully resolved.

RUN IT BACK

U.S. President Donald Trump subjected democratic peace theory to an intense test. He picked fights with European allies while praising Russian President Vladimir Putin and other dictators. Trump also cajoled and threatened liberal allies in other parts of the world, including East Asia. For a time, the United States seemed just as hostile toward fellow democracies as it was toward autocracies.

But under President Joe Biden, democratic peace is back in vogue. Like many of his predecessors, Biden has made promoting freedom a hallmark of his foreign policy. He has routinely described global politics as a contest between democracies and autocracies, featuring the United States and its allies in one corner and China and Russia in the other. Speaking at the UN in 2021, Biden pledged not to enter a “new cold war,” but he also announced that the world is at “an inflection point” and drew a sharp line between authoritarian and democratic regimes. “The future will belong to those who embrace human dignity, not trample it,” Biden said.

The president clearly aims to mobilize democracies, especially liberal industrial democracies, against dictatorships. His broad ideological framing emphasizes the threats posed by Russia to Europe’s democracies and by China to East Asia’s, including Taiwan. He has invoked ideology when promoting the importance of NATO in Europe and the Quad (the U.S. partnership with Australia, India, and Japan) in Asia and invested new resources in both bodies. Whether Biden wants it or not, the world may succumb to a new cold war. Much like the last one, it will be categorized by a clash between different systems of government.

States are already taking sides, lining up according to regime type. Democratic Finland and Sweden, neutral during the first Cold War, have joined NATO. Ireland has moved closer to the alliance. China and Russia have recruited Iran and North Korea to their team, fellow autocracies that are providing arms for Russia’s invasion of Ukraine. Russia has, in turn, used its UN Security Council seat to make it harder for the world to monitor North Korea’s nuclear program. China is buying up Iranian oil.

Under President Joe Biden, democratic peace is back in vogue.

This cold war—should the world indeed succumb to it—will be different from the first one. It pits democracies against autocracies, not capitalists against communists. Its geopolitics put a rising power (China) against an old hegemon (the United States), and an aggressive militarist (Putin) against an overstretched alliance (NATO). Every party sees itself on the defensive. The United States and its allies want a “world safe for democracy” in which national security is affordable, elections are secure, markets are free, and human rights remain an ideal. China, Russia, and their allies want a world safe for autocracy, where governments are free to skip elections and neglect human rights, where markets and information are subject to state direction, and where no one outside the government questions state policy. Both sides are threatened because those two visions are incompatible.

The divisions, of course, are not always so neat. As happened during the first Cold War, a number of developing countries, including some democracies, are seeking nonalignment. And as it did during the U.S.-Soviet standoff, Washington has autocratic partners, such as the Arab Gulf countries. But even within these relationships, ideology appears to be having an effect. The largest of the states in the neutral bloc, India, is partnering more closely with the United States as the two countries compete with Beijing, and both have repeatedly praised the other for being a democracy (even if India’s democracy is showing signs of distress). The United States and its liberal allies, meanwhile, are making authoritarian partners uneasy. Biden, for example, referred to Saudi Arabia as a “pariah” during his campaign, even though the United States has relied on Saudi oil production to help keep oil prices down.

The world’s great powers can still prevent these democratic-autocratic tensions from hardening into a full-blown cold war. Through effective diplomacy, they might be able to construct a kind of cold peace, or a détente in which countries shun subversive transformation in favor of mutual survival and global prosperity. Pursuing such a world may, indeed, be an obligation for democracies. As Kant insisted and Kennedy pleaded, in a responsible representative government, leaders must strive to protect free republics but also avoid unnecessary conflict.

Yet a true cold peace would require settling the war over Ukraine, creating a new understanding with Beijing and Taipei about the status of Taiwan, and striking arms control agreements—tasks that are nearly impossible. Instead, the world’s democratic powers appear to be girding themselves for a long twilight struggle with authoritarian regimes. This struggle may be scary, but it should not come as a surprise. It is, in fact, exactly what democratic peace theory predicts. Liberal states are being cooperative and peaceable toward fellow members of the club, working through institutions such as NATO and the Quad. But with respect to autocracies, they remain ready for war.