The so-called Islamic State, al-Qaeda and now the Taliban are radical jihadist groups focused on ridding the world from the threat, as they perceive it, that Western culture poses to Islam.
However, although broadly speaking they share a similar ideology, their views actually differ significantly – so much so that the three groups have often found themselves in conflict with one another.
And although there's no disputing the fact that IS have dominated the media in recent months, both al-Qaeda and the Taliban are still very much at large.
But what are the differences between these three prominent terrorist organisations?
Al-Qaeda follows Wahhabism – an extreme form of Sunni Islam that insists on a literal interpretation of the Koran.
The group was founded in 1988 in Pakistan by Osama Bin Laden and Mohammad Atif shortly before Soviet forces withdrew from neighbouring Afghanistan.
Al-Qaeda means 'foundation' in Arabic and they believe that they must use Jihad to mobilise their variation of Islam.
They believe in the concept of 'defensive jihad'; that is to say, it is every Muslim's obligation to fight those who might be seen as opposing Islam.
The terrorist group was behind the 9/11 attacks in 2001 in New York which killed 2,977 people.
The group viewed the West and its culture as a threat to Islam, and its main goal was to establish an Islamic state based on Sharia law.
However, experts argue that al-Qaeda has fragmented over the years into a variety of regional movements that have little connection with one another.
Watch: Afghanistan – world watches as Taliban enters Kabul.
The Taliban differ from al-Qaeda as many of their principles stem from the traditional Pashtun tribal way of life in Afghanistan, although both practise branches of Sunni Islam.
The group came to prominence in Afghanistan in the autumn of 1994, and governed in the country for five years, from 1996 to 2001.
Taliban means 'student' in Arabic, and it is widely speculated that the group first emerged from religious seminaries which preached a strict variation of Sunni Islam.
They originally promised to restore peace and security via Sharia law in the Pashtun areas of Pakistan and Afghanistan.
However, the group enforces extremely strict laws by which its citizens must live.
Women over the age of 10 are prohibited from receiving an education, and televisions and social media are banned.
Contrary to popular belief, there is not one single 'Taliban' but several different groups.
The biggest and most effective group in Pakistan are the TTP. It was this group that attempted to murder Malala Yousafzai for going to school under the group's rule.
Surprisingly, Afghanistan and Pakistani Taliban are rivals as well as allies; they have slightly conflicting ideologies which have led to clashes in the past.
Watch: 'We will burn your house' – Taliban hunts former UK staff unable to escape Afghanistan.
So-Called Islamic State
The so-called Islamic State was firmly established in 2014, in the weeks after Mosul was captured when Taliban commanders defected and swore allegiance to IS leader Abu Bakr al-Baghdadi.
The renegade commanders were mostly those who had grown dissatisfied with the leadership of Mullah Mohammed Omar, who at that time headed up the Taliban.
Although the media has been populated with stories of the IS over the last couple of years, the Taliban groups have a far larger following.
Although both practice extremist variations of Sunni Islam, Taliban groups teach a form of the Deobandi branch – which is actually less extreme than the version of the Wahhabi-Salafist tradition practised by IS and al-Qaeda.
Watch: Islamic State 'driving' UK terror threat.
While the Taliban and al-Qaeda predominately practise guerrilla warfare, making them extremely difficult to face using traditional combat techniques, IS tactics are far more similar to those of a typical army.
IS have also managed to harness the power of social media in a way that no preceding terrorist group has.
Using YouTube, Twitter, and WhatsApp, the group are able to spread terrorist propaganda inviting young people to join them in their fight against Western culture.
This has given them a huge advantage when it comes to luring potential recruits from overseas.
As of August 2016, it was estimated that about 850 British nationals had left the country to join the terrorist organisation – this number can only have grown in the last year.
A less well-known group is ISIS-K, a self-proclaimed branch of so-called Islamic State (IS), with the 'K' in the name standing for Khorasan – intending to represent the affiliate of IS in Afghanistan and Pakistan.
Watch: Who are ISIS-K?
ISIS-K was initially formed in 2015 by militants from Pakistan, as well as discontent Taliban members, and operates in the North and east of Afghanistan – close to Kabul, the nation's capital.
ISIS-K has a hostile relationship with the Taliban due to its more extreme version of Islam and have carried out a number of high-profile attacks in recent years – despite reports the group's numbers had fallen.
The ranks of ISIS-K have swelled as the Taliban's advance across Afghanistan has seen prisoners freed across the country.
US President Joe Biden says "justice has been delivered" as he confirmed Al Qaeda leader Ayman al-Zawahri was killed in a US drone strike in Afghanistan.