Today marks 17 years since the terrorist attacks of Sept. 11, 2001, a day commemorated with pledges to "never forget."

Our grief is well remembered. But too many of us have forgotten, or soon will, what followed on the heels of 9/11: our apparently endless war in Afghanistan.

Nearly two decades on, the longest conflict in U.S. history fades in and out of American consciousness — mostly out. The war has settled into grimly familiar patterns large and small. On a weekly and monthly level, the same headlines roll in again and again: A suicide bomber blows up a market, mosque, or other public venue, and dozens of innocents die. A coalition soldier is killed and a few more wounded. A high-ranking Islamic State, al Qaeda, Taliban, or other insurgency leader dies, and his role is soon refilled, hydra-like, by a new generation of radical.

Then there are patterns on a larger scale. Three presidential administrations from two political parties have overseen five troop surges, none of which has successfully broken the stalemate fight that has claimed tens of thousands of American and Afghan lives and has cost us trillions in taxpayer dollars.

We cycle through commanders, too. Last week, Gen. John Nicholson handed off leadership of NATO's Resolute Support Mission and U.S. forces in Afghanistan to Gen. Austin Miller. Carefully unmentioned in the Defense Department press release on the changeover is the fact that Miller will be the 18th — 18th! — officer to fill this role, succeeding Nicholson and the 16 commanders of the previous NATO mission in Afghanistan.

Nicholson is the only one of the lot to have lasted more than two years, and he ended his tenure with a simple message: "It is time for this war in Afghanistan to end."

"[Afghan] President [Ashraf] Ghani's courageous decision to announce a ceasefire over [the Muslim holiday of] Eid al Fitr unleashed the strong call of the Afghan people for peace," Nicholson said. "The entire world has witnessed this, and we support it. I believe some of the Taliban want peace also, but they are being encouraged to keep fighting. To the Taliban I say: 'You don't need to keep killing your fellow Afghans. You don't need to keep killing your fellow Muslims. The time for peace is now.'"

Nicholson has made this commendable — and eminently practical — push for local diplomacy repeatedly in recent months. The "U.S. is prepared to work with the parties to reach a peace agreement and political settlement to bring a permanent end to the war," he said in August. "At the end of the day, any negotiations over the political future of Afghanistan will be between the Taliban and the Afghan government. This must be an Afghan-led and Afghan-owned peace process, with Afghans talking to Afghans. And the U.S. is prepared to support, facilitate, and participate in these discussions."

The risk with Miller's takeover is that Nicholson's hard-won wisdom on this point will be lost, for Miller seems to incarnate our unique amnesia about this war: We forget that it is happening, and when we must remember, we forget that it is already lost.

The outgoing general's comparative realism was in scant supply in Miller's talk of being "relentless" in a "generational" fight to exterminate terrorism in Afghanistan. This disheartening enthusiasm to double down on the mistakes of the past — to make these counterproductive patterns even more permanent — suggests a dangerous failure "to distinguish what the U.S. military can do, what it cannot do, what it need not do, and what it should not do."

And that distinction grows more necessary with every passing day. We may be just months away from a truly new headline: "First American soldier born after 9/11 dies in Afghanistan."

That is a headline I pray we never see — but it is a headline we will see if Washington does not more aggressively pursue what Defense Secretary James Mattis has acknowledged to be the only viable route to stability in Afghanistan: "political reconciliation." (Last week's announcement that Zalmay Khalilzad, former U.S. ambassador to Afghanistan and Iraq, has been appointed special adviser to Afghanistan is welcome news on this front. Khalilzad will be "full-time focused on developing the opportunities to get the Afghans and the Taliban to come to a reconciliation," Secretary of State Mike Pompeo said. This role is long overdue.)

As Mattis and Nicholson have realized, there is no military victory to be had in Afghanistan. And we cannot simply stay forever. Diplomacy and political solutions are the best — and only — options. The U.S. military is by far the most powerful in the world, and it can do many things well. Nation-building Afghanistan is not one of them. Internal political problems will not be wiped away by an external military force.

What would happen if American troops withdrew from Afghanistan? My colleagues here at The Week expect "the government would surely fall. Afghanistan would once again become a Taliban-ruled medieval society, and al Qaeda and ISIS would have free rein there to plan and carry out attacks on the U.S."

That dire prediction may prove true, but it does not follow that American forces should stay in Afghanistan forever.

Nearly two decades of cyclical mistakes and setbacks have demonstrated this all too well. "U.S. troops have made considerable sacrifices," notes military historian Ret. Col. Andrew Bacevich. "The Pentagon has expended stupendous sums. Yet when it comes to promised results — disorder curbed, democracy promoted, human rights advanced, terrorism suppressed — the United States has precious little to show."

We will not have more to show if we spend another 17 years in the same patterns of failure, nor will we come any closer to righting the wrongs the original invasion sought to redress. It is time for these patterns of failure to be broken. It is time for this war in Afghanistan to end.