When President Bush announced the commencement of military operations in Afghanistan on October 7, 2001, the campaign was seen as a clearly justified response to the horrific attacks of 9/11. It was narrowly targeted on those responsible for the attacks, and it had three specific goals: to punish al Qaeda and degrade its ability to carry out future attacks; to punish and drive from power the Taliban regime that had harbored al Qaeda; and to send a clear message to every other country in the world: If you support those who have killed Americans, and who wish to kill more, you will do so at your own peril.

The Afghan war enjoyed overwhelming public support at the time. It doesn’t any longer. The public mood has shifted not because the original war aims were unjust—they were not—but rather because our war aims have changed, and they bear little resemblance to those that guided the U.S. military in late 2001 and early 2002.

Few Americans could have imagined in October 2001 that there would be nearly 100,000 U.S. troops on the ground in Afghanistan 10 years later. Few at the time would have supported a war that would cost more than $100 billion annually, as our current operations do.

As we look back over the last decade of war, we should be grateful for the sacrifices of our troops and their families. We should honor their service by remembering why they were sent to Afghanistan in the first place and by recommitting ourselves, and them, to a goal that is both achievable and essential. Tragically, the current mission is neither.

We lack the power, the wisdom, or the patience to create a functioning nation-state in Afghanistan. We need not do so in order to keep al Qaeda on the run. The 100,000 U.S. troops stationed there were essentially irrelevant to the assault that killed Osama bin Laden in neighboring Pakistan, and they are equally unnecessary in nearly all of the other operations conducted against al Qaeda over the past 10 years. The organization has been severely weakened and bin Laden’s killing could have served as a useful bookend to bringing the long war in Afghanistan to a suitable close.

It still can. Ten years is long enough. It is time to end the open-ended nation-building mission in Afghanistan and to bring our troops home.