In the February 2020 agreement reached with the US in Doha, the Taliban pledged to prevent al Qaeda and other terror groups from using Afghan soil to launch attacks abroad. Last week, Taliban spokesman Zabihullah Mujahid repeated the promise. “No death will be caused to anyone outside of Afghanistan … we will not allow anyone to use Afghanistan against them.”

Edmund Fitton-Brown, who leads the United Nations Monitoring Team on Afghanistan, noted in 2019 that the Taliban had “shown an iron self-discipline” in preventing threats to be projected outside Afghanistan by their own members or groups in areas they control.”

Control is the critical word. Afghanistan is a large mountainous country where communications and travel are difficult, where factions and warlords hold sway. It’s an immense task to extend the writ of government to far-flung provinces.

ISIS and the Taliban: Mutual loathing

While the Taliban’s connections with al Qaeda endure, both groups loathe ISIS, and the feeling is mutual. While al Qaeda sees Afghanistan as its historical hub and has fought alongside the Taliban, ISIS-Khorasan is the more violent interloper. Al Qaeda probably has several hundred fighters in Afghanistan, according to estimates by counter-terrorism experts, while ISIS-Khorasan may have between 1,500 and 2,000.

Ideologically and strategically, they are worlds apart.

“ISIS doesn’t believe in a political agenda,” said Clarke. “ISIS believes that only God can rule. And even though the Taliban is attempting to establish an Islamic emirate, that’s not enough for ISIS.”

ISIS is also viscerally sectarian, attacking minority communities such as the Shia and Sikhs. The Taliban have also been guilty of victimizing Afghanistan’s Shia minority, though are now trying to project a more tolerant image.

As Clarke puts it, in any place they control ISIS-K “are going to implement extremely harsh Sharia law. And they’re going to rule with an iron fist. They want to attract and recruit the most ardent sociopaths in the country and wanton violence helps them bring other fighters into the organization that have a similar mindset.”

ISIS-K leader Shahab al-Muhajir may hope to attract disenchanted jihadis from other groups if the Taliban is seen to “deal” with the West. ISIS scoffed at the Taliban victory, saying in its weekly online publication al Naba that “The victory of Islam will not come via hotels in Qatar nor the embassies in Iran and China.”

ISIS-K emerged in 2015 — at first in Baluchistan in Pakistan, before establishing itself in mountainous Afghan provinces such as Nangahar and Kunar. Some fighters came overland through Iran as ISIS came under pressure in Iraq and Syria.

Very soon it came to the cities, especially Jalalabad and Kabul, with its trademark mass casualty bomb attacks. According to UN figures, it launched 77 attacks in the first four months of this year.

Abdul Syed, a researcher and author on militant movements in Afghanistan and Pakistan, says that through devastating attacks in Kabul and Jalalabad, ISIS-K “has transformed to a new shape for a long battle in Afghanistan.” He told CNN that it enjoys support from radical Salafists in several provinces.

Its current strength may be reinforced by defectors and escapees from detention. Some captured ISIS-K fighters were being held in prisons near Kabul, which the Taliban overran as their offensive accelerated.

According to one regional counter-terrorism source, upwards of 100 and perhaps many more ISIS prisoners escaped – and have avoided re-arrest.

ISIS-K has proved resilient despite intense efforts by the Taliban, forces of the previous Afghan government and the US-led coalition to destroy it. The Taliban even claimed in 2019 to have wiped out the group in Kunar and Nangahar — but a year later ISIS-K freed hundreds of its fighters from the main jail in Nangahar.

Al Qaeda’s ‘force multipliers’

ISIS aren’t the only ones capitalizing on jailbreaks. As the Taliban emptied out prisons across Afghanistan in recent weeks, they set free hundreds of al Qaeda operatives, and there is continuing evidence of close ties between the Taliban and al Qaeda affiliates. The Haqqani Network, which straddles both groups, is now highly influential in Kabul.

US President Joe Biden has argued that the threat from al Qaeda has metastasized to places like Africa and Yemen. “There’s a greater danger from ISIS and al Qaeda and all these affiliates in other countries by far than there is from Afghanistan,” he said last week.

But the chairman of the Joint Chiefs of Staff, General Mark Milley, acknowledged in a recent briefing that groups like al Qaeda could reconstitute in Afghanistan in less than the two years previously estimated by the defense officials.

Al Qaeda’s leadership and ideological core remains in the mountains along the Afghan-Pakistan border. The US Defense Department said last year that al Qaeda’s affiliate in the region, al Qaeda in the Indian Subcontinent (AQIS), “maintains close ties to the Taliban in Afghanistan, likely for protection and training.”

That analysis was supported by the UN Monitoring Team on Afghanistan, who reported in June that “large numbers of Al-Qaida fighters and other foreign extremist elements aligned with the Taliban are located in various parts of Afghanistan,” estimating that the terror group has a presence in 15 of the country’s 34 provinces.

Raffaello Pantucci, a senior associate fellow at the Royal United Services Institute in London, says: “The idea that the Taliban would simply jettison such supporters after a glorious victory handed to them by God seems to miss a pretty fundamental point about the organization.”

The same applies to the Haqqani Network, which has several high-profile positions among the Taliban leadership. The UN report said that “contacts between al Qaeda and the Haqqani Network — including the Taliban’s deputy leader, Sirajuddin Haqqani — remain particularly close. They share long-standing personal relationships, intermarriage, a shared history of struggle and sympathetic ideologies.”

It is difficult to see these being shredded now that the Haqqanis are so influential in Kabul.

‘Over-the-horizon capability’

One question is to what extent US intelligence gathering in Afghanistan will be impaired now that it has no presence on the ground.

Biden has downplayed the risk, saying on August 16: “We’ve developed counterterrorism over-the-horizon capability that will allow us to keep our eyes firmly fixed on the direct threats to the United States in the region.”

In the wake of Thursday’s airport attack, Biden vowed retaliation. But there’s no substitute for eyes and ears on the ground, whatever satellite and surveillance technology offers.

US Defense Department spokesman Admiral John Kirby said last week the US did not think the number of al Qaeda fighters in Afghanistan was exorbitantly high but cautioned that “our intelligence-gathering ability in Afghanistan isn’t what it used to be because we aren’t there in the same numbers that we used to be.”

CIA Director William Burns had testified before Congress earlier this year that neither ISIS nor al Qaeda in Afghanistan had the capability to launch attacks inside the United States but said “when the time comes for the US military to withdraw, the US government’s ability to collect and act on threats will diminish. That’s simply a fact.”

Clarke concurs and adds that the primary threat from ISIS-K “would be to American interests in the region and potentially to Europe. It’s not impossible that ISIS-K could strike the US homeland, but I think the odds are quite minimal.”

Even if the Taliban were prepared to rein in al Qaeda and other groups, their ability to do so is far from certain. Last month Ken McCallum, director of the UK’s domestic intelligence agency MI5, spoke of the risk of “ungoverned spaces” emerging in Afghanistan.

There are other groups that see Afghanistan as a haven and pose a more regional threat.

Parts of the Pakistani Taliban (TTP), which have carried out dozens of attacks in their home country, have deep connections with their brethren in Kabul. Abdul Syed, who has studied the Pakistani Taliban in depth, notes that the fall of Kabul resulted in around 800 TTP prisoners being freed, including the group’s deputy emir. The TTP renewed their oath of allegiance to the Taliban and exhorted their members to follow in the footsteps of their Afghan counterparts.

“Efforts [by Pakistan] to force the Taliban’s hand might result in violent blowback, with Pakistani Taliban attacking targets inside Pakistan.”

China is anxious about Uighur jihadis using eastern Afghanistan as a launching pad for attacks inside the restive Muslim province of Xinjiang.

In recent months, according to intelligence sources and former Afghan officials, Uighurs belonging to the East Turkestan Islamic Movement (ETIM) have been in evidence in the province of Badakhshan, which shares a mountainous border with China.

Pantucci says that China’s pre-eminent concern is that Afghanistan will become a base for such groups. So far, he says, the Taliban have largely provided “rhetorical assurances” about Uighurs who might try to use Afghan territory to plot against Beijing.

Morale booster

At the very least, the fall of Afghanistan to the Taliban has boosted morale among al Qaeda sympathizers. One message widely distributed on jihadi forums hailed August 15 as a monumental day that had shown “what was taken by force can only be recovered by force.”

Likewise, al Qaeda’s most influential affiliate — al Qaeda in the Arabian Peninsula (AQAP) — celebrated the Taliban’s victory as the beginning of the Muslim nation’s advance towards “sovereignty, breaking the shackles of dependence and slavery, getting rid of tyrants and expelling the invaders from Muslim lands.”

The ISIS-K attack has had a similarly electrifying attack on ISIS supporters, with one supporter commenting “The head of America was rubbed in the dirt.”

The UN Monitoring Team’s report in June concluded that it was “impossible to assess with confidence that the Taliban will live up to its commitment to suppress any future international threat emanating from Al-Qaida in Afghanistan.”

The Taliban “will do what is required to be politic and try to establish their state, but fundamentally they believe the victory was given to them by Allah,” said Pantucci. “Why should they turn on their allies who fought with them?”