“For years the military graded its own homework and said it was winning,” said Mr. Dempsey “And civilians started wondering if we should be in Afghanistan, but did they call their congressmen? Did they protest in the street? No. Because there is no personal sacrifice. It’s easy to ignore a catastrophe when it isn’t yours.”

Now that it has come crashing down, he said, “no one quite knows what to say.”

When President Biden announced the remaining troops were leaving Afghanistan before the end of the summer, some members of the public felt like it was coming ten years or more too late.

“I always thought it would be difficult but not impossible to do what needed to be done in Afghanistan,” said Bryan Smith, a university administrator at Florida A&M University. “I also think we have not always taken into consideration that everybody doesn’t do democracy like we do.”

It wasn’t hard to find people who wanted to avoid the troubling questions of a long war by casting blame on one administration or another. It’s not as easy to dismiss those questions for the 775,000 military men and women who deployed there. All week veterans have been reaching out to one another, many have posted the phone number for veterans crisis hotlines on their social media.

At the Army post’s museum, Afghanistan is already an exhibit, complete with oil paintings of notable battles, showing uniforms already quaintly dated. The ground fought over in places like Kamdesh, recounted in that history, is already as unfamiliar to young soldiers as names like Somme or Khe Sanh.

On Friday, three privates who were in preschool in 2001 were taking a break at a local Starbucks near the post. Sipping fruit refreshers, they seemed to take the week’s developments in stride. The past may have been dismal, the present lacking the solemn recognition it might deserve, the future uncertain, but all three said they were there to do what the nation asked of them, whatever it might be. The fall of Kabul hadn’t changed that one bit.

One private, who declined to give his name because he wasn’t authorized to speak, said it didn’t bother him that the civilian world seemed to go on with little thought about the military efforts overseas.

“That’s what I want, that’s why I’m here,” he said. “I don’t want the country to have to worry.”

Campbell Robertson contributed reporting from Shanksville, Pa., Audra D. S. Burch from Hollywood, Fla., and Edgar Sandoval from San Antonio.