President George W. Bush ordered the U.S.-led invasion of Afghanistan in response to the Sept. 11, 2001 attacks. Some U.S. troops currently serving there had not yet been born when the World Trade Center collapsed on that crisp, sunny morning that changed how Americans see the world.
It only took a few months to topple the Taliban and send Osama bin Laden and top al-Qaida militants scrambling across the border into Pakistan, but the war dragged on for years as the United States tried establish a stable, functioning state in one of the least developed countries in the world. The Taliban regrouped, and currently hold sway over half the country.
The U.S. spent more than $750 billion, and on all sides the war cost tens of thousands of lives lost, permanently scarred and indelibly interrupted. But the conflict was also frequently ignored by U.S. politicians and the American public.
In the Qatari capital of Doha, U.S. Secretary of State Mike Pompeo will stand with leaders of the Taliban, who harbored bin Laden and his al-Qaida network as they plotted, and then celebrated, the hijackings of four airliners that were crashed into lower Manhattan, the Pentagon and a field in western Pennsylvania, killing almost 3,000 people.
It will likely be an uncomfortable appearance for Pompeo, who privately told a conference of U.S. ambassadors at the State Department this week that he was going only because President Donald Trump had insisted on his participation, according to two people present. It's not clear if he will actually sign the agreement.
Trump has repeatedly promised to get the U.S. out of its "endless wars" in the Middle East, and the withdrawal of troops could provide a boost as he seeks re-election in a nation weary of involvement in distant conflicts.
U.S. troops are to be withdrawn to 8,600 from about 13,000 in the weeks following Saturday's signing. Further drawdowns are to depend on the Taliban meeting certain counter-terrorism conditions, compliance that will be assessed by the United States.
Trump has approached the Taliban agreement cautiously, steering clear of the crowing surrounding other major foreign policy actions, such as his talks with North Korea.
Last September, on short notice, he called off what was to be a signing ceremony with the Taliban at Camp David after a series of new Taliban attacks. But he has since been supportive of the talks led by his special envoy, Zalmay Khalilzad.
Under the agreement, the Taliban promise not to let extremists use the country as a staging ground for attacking the U.S. or its allies. But U.S. officials are loath to trust the Taliban to fulfill their obligations.
The prospects for Afghanistan's future are uncertain. The agreement sets the stage for peace talks involving Afghan factions, which are likely to be complicated. Under the agreement, 5,000 Taliban are to be released from Afghan-run jails, but it's not known if the Afghan government will do that. There are also questions about whether Taliban fighters loyal to various warlords will be willing to disarm.
It's not clear what will become of gains made in women's rights since the toppling of the Taliban, which had repressed women and girls under a strict brand of Sharia law. Women's rights in Afghanistan had been a top concern of both the Bush and Obama administration, but it remains a deeply conservative country, with women still struggling for basic rights.