Since World War II, conventional interstate wars have become extremely rare, due to nuclear deterrence, the spread of democracy, globalization, and other forces. But the receding tide of interstate war has left us with a host of intractable civil wars. The collapse of the European empires after World War II, the disintegration of the Soviet Union, and the Arab Spring in 2011 all triggered conflict within states. Today, almost 90 percent of wars are civil wars, including prominent conflicts in Iraq, Syria, Libya, Yemen, Ukraine, Nigeria, and Gaza.

It’s true that most foreign internal conflicts don’t represent a major security threat to the United States. But globalization has increased our sensitivity to such wars, which can have an impact on U.S. interests and values by causing humanitarian crises, refugee flows, and terrorism. Since Vietnam, enemy countries have killed around 300 Americans, whereas insurgents and terrorists have killed more than 10,000 Americans.

In a world where nine out of ten wars are civil wars, almost every imaginable U.S. military operation will have a stabilization component. Even conventional interstate wars often evolve into nation-building missions, as we saw in Afghanistan and Iraq. Regime change can trigger the so-called Pottery Barn Rule: You break it, you own it.