The United States completed the withdrawal of its forces from Afghanistan, the Pentagon said on Monday, after a chaotic evacuation of thousands of Americans and Afghan allies to close out U.S. involvement there after 20 years of conflict.

The operation came to an end before the Tuesday deadline set by President Joe Biden, who has drawn heavy criticism from both Democrats and Republicans for his handling of Afghanistan since the Taliban made rapid advances and took over Kabul earlier this month.

The withdrawal was announced by General Frank McKenzie, commander of the U.S. Central Command, who said the final flights did not include some of the dozens of Americans who remained behind.

More than 122,000 people have been airlifted out of Kabul since Aug. 14, the day before the Taliban regained control of the country two decades after being removed from power by the U.S.-led invasion in 2001.

The United States and its Western allies scrambled to save citizens of their own countries as well as translators, local embassy staff, civil rights activists, journalists and other Afghans vulnerable to reprisals.

The evacuations became even more perilous when a suicide bomb attack claimed by Islamic State – enemy of both the West and the Taliban – killed 13 U.S. service members and scores of Afghans waiting by the airport gates on Thursday.

Biden promised after the bloody Kabul airport attack to hunt down the people responsible.

The departure took place after U.S. anti-missile defences intercepted rockets fired at Kabul’s airport.

Two U.S. officials said “core” diplomatic staff were among 6,000 Americans to have left. They did not say whether that included top envoy Ross Wilson, expected to be among the last civilians to depart.

A U.S. official said initial reports did not indicate any U.S. casualties from as many as five missiles fired on the airport. Islamic State claimed responsibility for the rocket attacks.

In recent days, Washington has warned of more attacks, while carrying out two air strikes. It said both hit Islamic State targets, one thwarting an attempted suicide bombing in Kabul on Sunday by destroying a car packed with explosives, but which Afghans said had struck civilians.

Tuesday’s deadline for troops to leave was set by Biden, fulfilling an agreement reached with the Taliban by his predecessor, Donald Trump to end the United States’ longest war.

But having failed to anticipate that the Taliban would so quickly conquer the country, Washington and its NATO allies were forced into a hasty exit. They leave behind thousands of Afghans who helped Western countries and might have qualified for evacuation.

Here’s a timeline of some of the biggest developments during the 20-year conflict.

• 7 October 2001: A US-led coalition bombs Taliban and al-Qaeda facilities in Afghanistan. Targets include Kabul, Kandahar and Jalalabad. The Taliban, who took power after a decade-long Soviet occupation was followed by civil war, refuse to hand over al-Qaeda leader Osama Bin Laden
• 13 November 2001: The Northern Alliance, a group of anti-Taliban rebels backed by coalition forces, capture Kabul
• 7 February 2009: US President Barack Obama approves a major increase in the number of troops sent to Afghanistan. At their peak, they number about 140,000
• 28 December 2014: Nato ends its combat operations in Afghanistan. With the surge now over, the US withdraws thousands of troops. Most of those who remain focus on training and supporting the Afghan security forces
• 29 February 2020: The US and the Taliban sign an “agreement for bringing peace” to Afghanistan, in Doha, Qatar. The US and Nato allies agree to withdraw all troops within 14 months if the militants uphold the deal
• 13 April 2021: US president Joe Biden announces that all US troops will leave Afghanistan by 11 September that year
• 16 August 2021: In just over a month, the Taliban sweep across Afghanistan, taking control of towns and cities all over the country, including Kabul. Afghan security forces collapse in the face of the Taliban advance
• 31 August 2021: The US completes its withdrawal from Afghanistan

SOURCE: REUTERS / BBC / AGENCIES