The longest war in American history might be coming to a close.

American forces have been in Afghanistan for nearly twenty years, but President Joe Biden is expected to announce that the U.S. military presence there will not enter a third decade.

According to the Washington Post, Biden will remove all troops from Afghanistan by September 11th, 2021, the 20th anniversary of the deadly attack that spawned the global war on terror.

“We’re going to zero troops by September,” a Biden administration insider told The Washington Post.

President George Bush launched “Operation Enduring Freedom” on October 7th, 2001. The initial phase – targeting the Taliban, which co-opted the Afghan government and harbored mass murderers – was brief and successful. But the U.S. eventually became stymied in unconventional warfare, bringing to mind the slow-bleed attrition of the Vietnam War.

Both presidents Obama and Trump repeatedly promised to remove all American troops from Afghanistan. They didn’t. Trump reportedly negotiated a deal with the Taliban setting a May 1, 2021 deadline for full removal, but he was voted out of office before that date. Biden had indicated that May 1 isn’t a realistic timetable.

There are currently 2,500 U.S. troops in Afghanistan, according to the Pentagon, although several media outlets report the number is closer to 3,500.

The Washington Post contextualizes Biden’s new deadline, which he is set to announce on Wednesday:

Biden’s decision comes after an administration review of U.S. options in Afghanistan, where U.S.-midwived peace talks have failed to advance as hoped and the Taliban remains a potent force despite two decades of effort by the United States to defeat the militants and establish stable, democratic governance. The war has cost trillions of dollars in addition to the lives of more than 2,000 U.S. service members and at least 100,000 Afghan civilians.

“This is the immediate, practical reality that our policy review discovered,” the person familiar with the deliberations said. “If we break the May 1st deadline negotiated by the previous administration with no clear plan to exit, we will be back at war with the Taliban, and that was not something President Biden believed was in the national interest.”

A senior Biden official said “The president has judged that a conditions-based approach, which has been the approach of the past two decades, is a recipe for staying in Afghanistan forever,” according to Politico.

The official added that Biden “has long known that military force would not solve Afghanistan’s internal political challenges,” and “would not end Afghanistan’s internal conflict.”

Politico warns that the new deadline “will likely prompt the Taliban to renew attacks” on American forces. More from Politico:

Gen. Frank McKenzie, head of U.S. Central Command, recently warned that if the American pullout goes ahead before diplomatic efforts between the Taliban and the Afghan government can yield a deal, fighting will intensify across the country.“

If we withdraw and no deal was made with the Taliban, I think the government of Afghanistan is going to be in for a very stiff fight to retain possession” of urban population centers, McKenzie warned.

Military leaders, particularly in the special operations community, are concerned that when the U.S. withdraws, the terrorist threat will evolve and grow in Afghanistan’s vast uncontested regions, said one former military official familiar with the discussions.

Senate Minority Leader Mitch McConnell, a Republican, called Biden’s forthcoming announcement “a grave mistake. It is a retreat in the face of an enemy that has not yet been vanquished, an abdication of American leadership.”

Rep. Elissa Slotkin (D-MI), a former CIA agent and Middle East Analyst, “tentatively supported the move,” according to The Washington Post, “but said Congress would need a full accounting of plans to secure U.S. diplomats in Afghanistan and ensure that global extremists from al-Qaeda and the Islamic State are unable to gain renewed strength.”