US President Joe Biden says he will withdraw remaining American troops from Afghanistan, declaring the 9/11 attacks "cannot explain" why their forces should still be there 20 years on.
Mr Biden vowed not to pass the longest war in his country's history on to another president, adding that the US cannot continue to pour resources into an intractable war and expect different results.
The drawdown would begin, rather than conclude, by 1 May, which has been the deadline for full withdrawal under a peace agreement the Trump administration reached with the Taliban last year.
"It is time to end America's longest war," Mr Biden said, but he added that the US will "not conduct a hasty rush to the exit".
"With the terror threat now in many places, keeping thousands of troops grounded and concentrated in just one country and across the billions [of dollars spent] each year makes little sense to me and to our leaders," Mr Biden said.
"We cannot continue the cycle of extending or expanding our military presence in Afghanistan, hoping to create ideal conditions for the withdrawal and expecting a different result.
"I am now the fourth United States president to preside over an American troop presence in Afghanistan.
"I will not pass this responsibility to a fifth," he added.
As Barack Obama's vice president, Mr Biden advised the 44th president to tilt towards a smaller counterterrorism role in the country while military advisers were urging a troop build-up to counter Taliban gains.
Mr Biden has also made clear he wants to recalibrate US foreign policy to face bigger challenges posed by China and Russia.
However, withdrawing all US troops comes with the risk of boosting the Taliban's effort to claw back power and undo gains toward democracy and women's rights made over the past two decades.
NATO chief Jens Stoltenberg later said the alliance has agreed to withdraw its roughly 7,000-strong forces from Afghanistan to match US President Joe Biden's decision.
Mr Stoltenberg said the full withdrawal would be completed "in months", but did not mention the 20th anniversary of the 9/11 terrorist attacks set as a goal by Mr Biden.
"We went into Afghanistan together, we have adjusted our posture together and we are united in leaving together," he said.
The UK will "drawdown" from Afghanistan along with NATO, according to Defence Secretary Ben Wallace, with discussions to be had with allies about the precise details.
Cover image: US Army.