The final collapse of the 20-year western mission to Afghanistan took only a single day as Taliban gunmen entered the capital, Kabul, on Sunday, President Ashraf Ghani fled the country, and America abandoned its embassy in panic.

Even the militants themselves were surprised by the speed of the takeover, co-founder Mullah Abdul Ghani Baradar admitted in a video statement in the evening. Now the group faces the challenge of ruling, he added. They are expected to proclaim a new Islamic Emirate of Afghanistan soon.

Many in Kabul do not trust promises made by the former insurgents of an amnesty for their old enemies and those, like women's rights activists, who sought a different future for Afghanistan. The airport was mobbed with thousands of people desperate to escape. In the evening they flooded on to the runway, halting all air traffic.

In deeply humiliating scenes for the Biden administration, less than a month before the 20th anniversary of the 9/11 attacks on America, smoke spiralled from the embassy compound as staff hastily destroyed documents, before a final group took down the stars and stripes flag and headed to the airport by military helicopter.

It was clear from early Sunday that a second era of Taliban rule had effectively begun. Taliban commanders started the day so confident of victory that after their fighters surrounded the capital, they ordered them to stay outside the city and wait.

"Our forces are not entering Kabul city. We want a peaceful transfer of power," said spokesman Suhail Shaheen. But with surrender apparently inevitable, Afghan government forces melted away, looting broke out, and hours later the Taliban claimed their men were needed to restore order.