The events in Afghanistan are part of a much bigger story, and they illustrate that story with painful clarity. Rarely is the contest between “open” and “closed” societies, between democracy and dictatorship, between freedom and autocracy so crystal clear; rarely has the victory of the latter over the former been so rapid or so complete. A Hugo Chávez or a Vladimir Putin needs years to impose repressive control on their nation. The Taliban might carry it off in days or weeks.

For that reason, the fall of Kabul will necessarily cause some U.S. allies to question whether their own liberal society is safe. They understand why Americans were tired of Afghanistan; maybe it’s true that the country was too distant, too alien, to justify a continued presence, as Biden has so forcefully said. But which countries are close enough, or culturally similar enough, to be confident of long-term American support? They aren’t at war right now, but still: If the U.S. military were to abruptly withdraw air support and logistics from Europe, say, or from the South Korean peninsula, then many countries might suddenly find themselves vulnerable to aggression. Germany would not be able to defend itself from one day to the next. Nor would Poland. Or Estonia. Or Japan. An enormous question mark lies, of course, over the islands of Taiwan.

The fall of Kabul should refocus Americans—in the administration, in Congress, in the leadership of both parties, but above all, ordinary Americans across the country—on the choices that are now coming thick and fast. Afghanistan provides a useful reminder that while we and our European allies might be tired of “forever wars,” the Taliban are not tired of wars at all. The Pakistanis who helped them are not tired of wars, either. Nor are the Russian, Chinese, and Iranian regimes that hope to benefit from the change of power in Afghanistan; nor are al-Qaeda and the other groups who may make Afghanistan their home again in future. More to the point, even if we are not interested in any of these nations and their brutal politics, they are interested in us. They see the wealthy societies of America and Europe as obstacles to be cleared out of their way. To them, liberal democracy is not an abstraction; it is a potent, dangerous ideology that threatens their power and needs to be defeated wherever it exists, and they will deploy corruption, propaganda, and even violence to do so. They will do it in Syria and Ukraine, and they will do it within the borders of the U.S., the U.K., and the EU.