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?