A withdrawal that was planned and led by Trump up until Biden took over.

https://en.wikipedia.org/wiki/2020%E2%80%932021_U.S._troop_withdrawal_from_Afghanistan

As part of the United States–Taliban deal, the Trump administration agreed to an initial reduction of US forces from 13,000 to 8,600 troops by July 2020, followed by a complete withdrawal by 1 May 2021, if the Taliban kept its commitments.[10] At the start of the Biden administration, there were 2,500 US soldiers remaining in Afghanistan and, in April 2021, Biden said the US would not begin withdrawing these soldiers before 1 May, but would complete the withdrawal symbolically by 11 September.[11][12]The Taliban began a final offensive on 1 May and, on 8 July, Biden moved up the completion date to 31 August.[13][14] There were about 650 US troops in Afghanistan in early August 2021, tasked with protecting Hamid Karzai International Airport and the US Embassy in Kabul.[15][16]NATO's Resolute Support Mission concluded on 12 July 2021[17] while US intelligenceassessments estimated as late as July that Kabul would fall within months or weeks following withdrawal of all American forces from Afghanistan, the security situation deteriorated rapidly