Foreign Policy Question

On October 7, 2001, the United States launched its war in Afghanistan.

Today, April 17, 2018, we are still there. That was 6,036 days ago.

Starting in October 2019 (presuming we are still there, and I have no good faith reason to believe we won't be) the United States military will be sending soldiers to fight a war for which they weren't even alive when it started; they will never have known a world where we (I use that term loosely, to reference the United States as a whole) were not fighting a war in Afghanistan.

I want the war to end. Yesterday.

I have no moral qualms with the effort itself, but I believe that all we reasonably can accomplish in Afghanistan has been accomplished.

My question, for those who support a continuing presence there, is this: What objective, measurable "thing" could convince you that we have won the War in Afghanistan and the troops can now come home?

Answers along the lines of "make it so that terrorists can't have a safe haven there" or "when they have freedom and liberty" by the way don't count unless the proponent of such answer can provide the objective and measurable metrics associated with "freedom," "liberty," or "non-safe haven."

My son is 5 years old. The war was more than a decade old when he was born in 2012. I don't want him or his cohorts to still be fighting that war when they become adults, though I could be convinced if the proponents of the war can explain to me what it is that they want. What objective fact would make this hypothetical foreign policy hawk (i.e. John Bolton) satisfied?

I generally tend to avoid writing about foreign policy because, aside from living outside of Toronto for a few years when I was young, I have scarcely even been outside of America; I certainly do not have the kind of expertise that one would expect to consider someone knowledgeable on foreign affairs. However, after speaking of the seemingly neverending Afghan War with my neighbor, I felt the need to speak up on the blog as well.