How Civil Wars Start

Until quite recently, a civil war seemed all but impossible in the United States—something of the past, for most citizens, not of the future.

But the Capitol insurrection on Jan. 6 and the rise of violent domestic extremism have set off alarm bells about the potential for another descent into internal war. That may seem far-fetched, but there have been literally hundreds of internal conflicts around the world—in countries from Afghanistan to Zimbabwe. And more depressingly, in many ways, the U.S. Civil War never actually ended and may indeed be ramping back up.

Even with U.S. President Joe Biden in firm control, recent events make the risk of wider political violence painfully obvious.

Civil wars are unique in their specific causes, the ways they escalate from clashing interests to violence and the ways they de-escalate, but all civil wars share at least three features in common. First, most civil wars follow some prior conflict (often a previous civil war or, more accurately, the highly skewed and politicized memory of a past civil war). The new belligerents nor the issues need not be exactly the same as the old. Most often, a charismatic leader spouts a narrative about past glory or humiliation that suits their ideology, political ambitions, or even flows from simple historical ignorance.

Second, national identity is divided along some critical axis, such as race, faith, or class. All countries have fracture lines and cleavages, but some divides are deeper than others. Even initially minor cleavages may be exploited by domestic or foreign actors committed to redistributing wealth or power. For example, the Soviet Union (and now Russia) has successfully devoted serious resources to destabilizing the United States and its allied democracies by intensifying existing cleavages....