Were you willing to sacrifice a son or daughter to save Afghanistan?

The fall of Afghanistan was predictable, but even the most pessimistic foreign policy experts must be surprised by the rapidly developing momentum of the Taliban's push to establish complete control of the country.

Last week, the Taliban rapidly overwhelmed provincial capitals and major cities, including Kandahar, Afghanistan's second largest. Now, they have entered Kabul, and Afghanistan's president, Ashraf Ghani, has fled. The prospects are dire.

The violence and the fear of Taliban rule have provoked a refugee crisis. A United Nations agency reports that a quarter of a million Afghans have fled this summer, either to the comparative security of Kabul or to other countries. Food and shelter are scarce. A spokesman for a food distribution program says, "We fear the worst is yet to come and a larger tide of hunger is fast approaching."

But the immediate approaching tide is the terror that spreads in front of Taliban advances. Who has cause to be afraid? Certainly all government officials do, as well as anyone suspected of supporting the American military effort of the last two decades. Journalists have every reason to be terrified, as well. A considerable number have already been assassinated or forced to flee.

Intellectuals and teachers are at risk, as is anyone with the slightest inclination to tolerate any religion but Islam or any version of Islam less rigid and coercive than the version the Taliban will impose on Afghanistan. Homosexuals? Don't even ask.

But the Afghans with the most to fear are probably women and girls, who have experienced two decades of comparative freedom and rights. When the Taliban reclaim control, all of that will be lost. Education for females will be prohibited. Taliban enforcement squads will undoubtedly again patrol the streets to beat with canes any women out of compliance with a strict Islamic dress code.

But the Taliban aren't merely rigid fundamentalists who intend to enforce a severe, inflexible version of Islam. There are ample reasons for the terror that is spreading before the Taliban's rapid return to power, but a single example will serve:

This is pure savagery. But this incident is no aberration. It represents the measure of brutality that the Taliban mean to impose under their rule. It's a brand of evil that deserves to be annihilated with military force, without mercy.

But this crisis provokes a question: What are we willing to do to save Afghanistan? This question is clarified by a more precise question: Are you and I willing to sacrifice a son or daughter in combat so that young Afghan girls can go to school? I suspect that for most of us the answer is no.

If that answer sounds unduly severe or heartless, we can relieve some of its moral ambiguity by raising another question: Could any amount of blood, resources and accumulated decades of effort have changed the outcome in Afghanistan?

At present it looks highly doubtful. If only we had had the wisdom to ask ourselves this question before we invaded Afghanistan in October of 2001 or, more fatally, before we were lulled into staying for two decades with little understanding of the culture, our goals or the likelihood of achieving them.

My own generation's war, Vietnam, would have been a good place to start thinking about this. Or we might have asked this question before invading Iraq. At the least I hope we'll remember to think about nearly all of our post-World War II military history before we invade Iran.