A Timeline

'War on terror': On October 7, 2001 -- less than a month after the September 11 attacks that killed around 3,000 people in the US -- President George W Bush launches "Operation Enduring Freedom" in Afghanistan. The ruling Islamist Taliban had been sheltering Osama bin Laden and his Al-Qaeda movement, which carried out the 9/11 attacks. The operation opens a military front in the US "war on terror" and within weeks, US-led forces overthrow the Taliban, in power since 1996.

Overshadowed by Iraq: American attention is diverted from Afghanistan when US forces invade Iraq in March 2003, to oust dictator Saddam Hussein. The fragmented Taliban and other Islamist outfits regroup in their strongholds in southern and eastern Afghanistan, from where they travel between their bases in neighbouring Pakistan's tribal areas, and launch an insurgency.

Peak of 100,000 US troops: In 2009, Barack Obama -- elected president after a campaign that promised to end the Iraq and Afghanistan wars -- boosts the US presence to around 68,000. In December, he sends another 30,000 troops. The objective is to stymie the growing Taliban insurgency and strengthen Afghan institutions. By 2010 about 150,000 foreign soldiers are deployed in Afghanistan, of which 100,000 are American.

Bin Laden killed: Osama bin Laden is killed on May 2, 2011 in a US special forces operation in Pakistan. The Nato alliance ends its combat mission in Afghanistan in 2014, but around 12,500 foreign soldiers -- of which 9,800 are American -- remain to train Afghan troops and conduct anti-terrorist operations.

Doha Peace Talks: In 2018, Washington and Taliban representatives discreetly open talks in Doha focused on slashing the American military footprint in Afghanistan. In return, Washington demands that the Taliban prevent the country from being used as a haven for jihadist groups. On February 29, 2020 the US and Taliban sign a historic deal paving the way for the withdrawal of all foreign forces from Afghanistan by May 2021.  The insurgents in return offer some security guarantees, and agree to hold peace talks with the Afghan government.

Taliban sweep to power : Troop numbers by the end of Trump's presidency in January 2021 fall to 2,500 as support for military action wanes. At the end of April Nato begins a concurrent withdrawal of its mission involving 9,600 soldiers. President Joe Biden says he will stick to the agreement with the Taliban, but delays the drawdown deadline until September 11. Officials on June 2 announce the departure of all US and Nato troops from Bagram, Afghanistan's biggest air base. On August 15, the Taliban sweep into Kabul, with tens of thousands of Afghans and foreigners rushing to the airport in a desperate bid to scramble onto evacuation flights. More than 123,000 people are airlifted out of Kabul. Just hours before the August 31 deadline, the remaining American troops fly out.