In the wake of the Cold War, as globalisation gathered speed, commentator Thomas Friedman observed ^[1] that no two countries with a McDonald’s franchise had ever gone to war with each other. This led him to what he called the ‘golden arches theory of conflict prevention’: when a country reaches a certain level of economic development—one where the middle class is big enough to support a McDonald’s—its people lose interest in fighting wars. The key to peace, the logic went, may well lie in economic development and interconnectedness.

It was not long before Russia disproved ^[2] Friedman’s theory—first with its 2008 invasion ^[3] of Georgia, and again with its 2014 invasion ^[4] of Ukraine. Now, Russia has launched an all-out military campaign aimed at conquering Ukraine and returning its lands and people to ‘Mother Russia ^[5].’ Economic ties alone, it seems clear, are not enough to preserve peace.

Many now view economic engagement as a liability. After all, countries like Germany and Italy, with their heavy dependence on Russian energy, are effectively hostages to the Kremlin’s militarism. Severing trade and commercial ties with Russia is now the order of the day. Russia has even ceased to be a ‘McDonald’s country’: the company announced in March that it was closing ^[6] all 850 of its franchises in the country.

Friedman was far from the first to suggest that economic and commercial relations have a pacifying impact on international relations. French philosopher Montesquieu argued ^[7] that ‘the natural effect of commerce is to dispose us to peace.’ American revolutionary Thomas Paine went further ^[8]: ‘If commerce were permitted to act to the universal extent it is capable, it would extirpate the system of war.’ In the 19th century, British politician and industrialist Richard Cobden campaigned for free trade on the grounds ^[9] that it ‘would have the tendency to unite mankind in the bonds of peace.’

Such arguments are based not only on the idea that countries have an economic interest in maintaining the commercial bonds they have forged. Rather, the Enlightenment theory of doux commerce ^[10] (gentle commerce) held that trade has a civilising effect on society, because it depends on social interactions with diverse people, as well as principles like fairness and reciprocity.

The doux commerce theory has had plenty of critics; there was clearly nothing ‘gentle’ about the slave trade, or about imperial powers stripping colonies of raw materials for manufacture back home. But nor can we ignore that war is now essentially unthinkable among the members of the European Union, including the eight Central and Eastern European countries that joined ^[11] the union after the Cold War’s end.

Why doesn’t Russia fit this pattern? The answer might lie in its political exclusion.

After the fall of the Soviet Union, the former members of the Warsaw Pact ^[12] were offered not only trade packages, but also a host of opportunities to connect to networks of European regulators, judges, legislators and civil society, even before they became candidate EU members. Those without EU prospects joined NATO, leading to some military integration and a sense of membership in the Western club.

Not Russia. In 2000, Vladimir Putin proposed ^[13] to Bill Clinton that Russia could join NATO, but the step was never taken. Had it been, it would have fundamentally changed Russia’s geopolitical incentives, though it would also have changed NATO dramatically.

In any case, that ship has sailed. Putin’s war on Ukraine has revived and strengthened NATO as an anti-Russia alliance, with Finland and Sweden ^[14] now likely to become members. On top of this, the EU has awarded Ukraine and Moldova candidate status ^[15], and EU Commission President Ursula von der Leyen ^[16] has laid out a kind of Marshall Plan for Ukraine ^[17] aimed at enabling the country to make rapid progress after the fighting stops.

Simply put, Putin’s war has united the West ^[18]. The task now is to uphold that unity long enough to ensure that Putin incurs such losses for his aggression that he is permanently deterred from further efforts to expand Russia’s borders by force.

But there is an even bigger challenge on the horizon. The West will never have truly peaceful relations with Russia without a significant degree of economic, political and social integration.

Western strategists should therefore be thinking not only about how to defeat and deter Russia (and rebuild Ukraine), but also about how eventually to roll back sanctions against Russia and create incentives for a new generation of Russian leaders to develop political and economic relations with the West. A combination of political and economic engagement ^[19] was, after all, vital to the success of the Marshall Plan in Western Europe and the reintegration ^[20] of Japan into the global economy after World War II.

Similar logic applies to China. Many commentators excoriated ^[21] former US president Donald Trump for withdrawing the United States from the Trans-Pacific Partnership, a trading bloc encompassing 12 Pacific Rim countries—and excluding China. In their view, the TPP was essential to enhance America’s influence in a critical region, while diminishing China’s.

But, while Trump’s policy was far from prudent, isolating China is a bad idea. Doing so risks empowering hardliners in the Chinese leadership and increasing China’s incentive to behave antagonistically, or even aggressively. Instead, the US should join ^[22] the Comprehensive and Progressive Agreement for Trans-Pacific Partnership (the TPP’s successor) and back China’s inclusion.

The doux-commerce effect depends on economic and political inclusion. That is a tall order in today’s world, and it certainly cannot be achieved overnight. But as we seek to meet the short-term imperative of ending Russia’s aggression, we must also devise a longer-term strategy for building a more peaceful and prosperous world.