Officials have said at least 13 US troops and 60 Afghan nationals were killed – and more than 150 people were injured – in a “complex attack” outside Hamid Karzai International Airport in Kabul on 26 August.
The Afghan offshoot of Isis - known as Isis-K - carried out the bloody attack in the final days of the evacuation effort which killed two Britons and the child of a British national.
Here is everything you need to know about it.
What is Isis-K?
Founded in 2015, Isis-K is the branch of the so-called Islamic State in the Khorasan region, which historically covers parts of Iran, Afghanistan and Pakistan.
Formed by militants from Pakistan along with disaffected Taliban members, it operates mainly in the north and east of Afghanistan close to Kabul.
Isis-K has carried out a number of high-profile attacks in recent years, including a devastating attack on a maternity hospital in Kabul in May 2020, killing 24 people including newborn babies.
It has also claimed responsibility for an assault on the city’s university last November and rocket attacks in the same month; Isis-K also claimed responsibility for an attack on Jalalabad prison last August.
Are they a threat?
The group is able to carry out deadly attacks in the area, and US secretary of state Antony Blinken previously described the threat of an Isis-K attack as “a very real possibility”.
But the former head of British forces in the country has said it might not be “the main threat”, and that the combined menace of a number of groups could be the real worry in Afghanistan.
Colonel Richard Kemp told BBC Breakfast: “That threat of terrorist attack, whether it’s from Taliban, the Islamic State, or al Qaida, it could equally be all three of those groups.
“The fact that people are talking about Islamic State doesn’t make that the most likely threat.”
Recent events in the country may also have disastrous side effects going forward, inspiring other groups around the world to carry out deadly attacks.
Conservative MP - and former territorial Army soldier who served in Afghanistan - Tom Tugendhat has said Western powers must ensure they have not thrown “a tonne of fuel” over the ambitions of other terrorist groups by withdrawing from Afghanistan.
“The reality is there are many other groups that have drawn inspiration from this – Al-Shabaab in the Horn of Africa, Boko Haram in Nigeria, al-Qaeda in the Islamic Maghreb in Mali,” he told BBC News.
A former vice chief of staff of the United States army described the country’s withdrawal from Afghanistan as “one of the most serious foreign security blunders the US has made in the past 30 or 40 years”.
Speaking on BBC Radio 4’s Today show, General Jack Keane said: “The reality is that al-Qaeda is in 15 provinces in Afghanistan. Isis-K has aspirations outside of Afghanistan.”
Keane added that he believes the deadline to leave should have been pushed back in order to evacuate more people, and that a “modest force” presence could have been retained.
What is their relationship with the Taliban?
A recent UN Security Council report suggested there were between 1,000 and 2,200 Isis-K fighters, but their ranks may have swelled in recent weeks.
Isis-K is hostile towards the Taliban - which has condemned the attack - due to its more extreme version of Islam, and the two groups have previously fought over control of territory in Afghanistan.
After the Taliban’s takeover of the country last week, the group reportedly executed a senior Isis-K commander who had been imprisoned in Kabul.
The conflict between the two groups means that Isis-K is less likely to be bound by the Taliban’s agreement with Western forces to allow evacuations to continue from Kabul airport.
Tugendhat has dismissed suggestions the Taliban were now on the same side as coalition troops.
He said: “[Isis-K] is an organisation that has been hosted by the Taliban in various different ways, they are now complaining that the dog they taught to bite is biting.”
He said Islamic State and the Taliban had “housed and husbanded each other” in various ways for many years.
How can they be stopped?
Former military commander General Sir Richard Barrons said that the UK will need to form a relationship with the Taliban in order to “get on top of” Isis-K.
“It is a very strange state of affairs and I think we are now going to have to bite our lip more and be very pragmatic because we have now got two huge problems to overcome,” he told BBC Radio 4’s Today programme.
“The first is, a lot of people to whom we have made a commitment are now going to be left behind.
“The only way we are going to be able to get on top of [Isis-K] is by forming a relationship with the Taliban, since we no longer have an embassy, troops on the ground, or a relationship with the Afghan security forces.”
British forces are prepared to launch air strikes to target so-called Islamic State terrorists in Afghanistan, the head of the RAF has indicated.
The UK and US remain willing to take on Islamic State, also known as Daesh, and Foreign Secretary Dominic Raab has said the global coalition against the terrorist group was ready “to combat Daesh networks by all means available, wherever they operate”.
Air Chief Marshal Sir Mike Wigston indicated the RAF could strike Isis-K targets in Afghanistan.
“Ultimately what this boils down to is that we’ve got to be able to play a global role in the global coalition to defeat Daesh, whether it’s strike, or whether it’s moving troops or equipment into a particular country, at scale and at speed,” he told the Daily Telegraph.
“If there’s an opportunity for us to contribute I am in no doubt that we will be ready to – that will be anywhere where violent extremism raises its head, and is a direct or indirect threat to the UK and our allies.”
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