Afghanistan: Will it become haven for terror with the Taliban in power?
The Taliban are back, 20 years after being ousted for supporting terror groups. Will they do the same?
In remote, pine-clad valleys of Afghanistan's Kunar province and in online jihadist chat forums there is jubilation at what al-Qaeda supporters see as "a historic victory" by the Taliban.
The humiliating departure of the very forces that temporarily expelled both the Taliban and al-Qaeda 20 years ago has come as a massive morale boost to anti-Western jihadists all over the world.
The potential hiding places for them now opening up in the country's ungoverned spaces are a tempting prize, especially for Islamic State (IS) group militants looking to find a new base after the defeat of their self-declared caliphate in Iraq and Syria.
Western generals and politicians are warning that the return of al-Qaeda to Afghanistan, in strength, is "inevitable".
UK Prime Minister Boris Johnson, speaking after an emergency crisis meeting, warned that Western nations needed to unite to prevent Afghanistan lapsing back into becoming a haven for international terrorist groups.
And on Monday UN Secretary-General Antonio Guterres called on the UN Security Council to "use all tools at its disposal to suppress the global terrorist threat in Afghanistan".
But does a Taliban return automatically translate into a return of al-Qaeda's bases and a subsequent platform for transnational terror attacks targeting Western countries, amongst others?
Not necessarily, no.
Quest for legitimacy and recognition
The last time the Taliban governed the whole country, from 1996-2001, Afghanistan was practically a pariah state.
Only three countries, Saudi Arabia, Pakistan and the United Arab Emirates, recognised their legitimacy.
As well as brutalising their own population, the Taliban provided safe sanctuary for Osama Bin Laden's al-Qaeda organisation which orchestrated the 9/11 attacks on the US in 2001, killing nearly 3,000 people.
An estimated 20,000 recruits from all over the world passed through al-Qaeda's training camps, learning lethal skills and creating what became known as "a university of terror" as they dispersed back to their own countries.
Today the Taliban still see themselves as the rightful - if unelected - rulers of "the Islamic Emirate of Afghanistan" and they will want some degree of international recognition.
They already appear keen to project the idea that they have come to restore order, calm and authority, after the corruption, infighting and waste that has characterised much of government over the last 20 years.
During the failed peace talks that took place in Doha, it was made clear to Taliban negotiators that this desired recognition could only come if they disassociated themselves completely from al-Qaeda.
We have done already, said the Taliban. No they haven't, says a recent UN report which pointed out the close tribal and marital links between the two groups.