Six years ago, the Islamic State-related group that Americans blamed for Thursday’s suicide attacks at Kabul airport was formed in eastern Afghanistan. It quickly grew to be one of the most dangerous terrorist threats worldwide.

Despite being under constant military attack by the U.S.-led Coalition, Islamic State Khorasan survived and is now able to press for more attacks as the United States and NATO partners withdraw from Afghanistan and the Taliban return to power.

In sticking to a Tuesday deadline for withdrawing U.S. troops from Afghanistan, President Joe Biden mentioned the threat of Islamic State terrorist attacks. U.S. General Frank McKenzie stated at a Pentagon news conference Thursday that officials believe Islamic State fighters carried out Thursday’s attacks. He also mentioned the possibility of a bomber being able to slip into Afghan crowds near U.S. military personnel.

This group has a track record of highly lethal attacks despite its heavy losses. Here’s a look at the deadly group that influenced the course of the Kabul airlifts, and U.S. actions.

What is ISLAMIC STATE KHORASAN?

In the months following the march of core Islamic State fighters across Syria and Iraq, the Central Asia branch of the Islamic State sprung up. It was able to create a self-proclaimed caliphate or Islamic empire in the summer 2014. It took five years for international and local forces to overthrow the caliphate in Syria and Iraq.

The name of the Afghanistan affiliate comes from the Khorasan Province. This region was a large part of Afghanistan, Iran, and central Asia during the Middle Ages.

This group is also known by ISK or ISIS K.

Who are THE FIGHTERS OF ISLAMIC STATE KHORASAN?

After being expelled from Pakistan, several hundred Pakistani Taliban fighters fled to Afghanistan and sought refuge at the border. Others joined them, including disgruntled Afghan Taliban fighters who were unhappy with the Taliban’s peaceful and moderate ways, unlike the West.

In recent years, the Taliban sought peace negotiations with the United States. However, the discontented Taliban moved more to the Islamic State, which increased its numbers. Many were disappointed that the Taliban was seeking negotiations with the U.S. when they believed the movement was marching to a military victory.

This group has also attracted significant numbers from the Islamic Movement of Uzbekistan (a neighboring country); fighters from Iran’s only Sunni Muslim majority Province; and members of Turkistan Islamic Party, which includes Uighurs from China’s northeast.

Many were drawn to the Islamic State’s extreme and violent ideology. It also promised a caliphate that would unify the Islamic world. This goal was never pursued by the Taliban.

What IS THE KEY TO MAKE THEM A POWERFUL THREAT?

The Taliban have limited their fight to Afghanistan. However, the Islamic State group of Afghanistan and Pakistan has accepted the Islamic State’s call to a global jihad against all non-Muslims.

The Center for International and Strategic Studies counts dozens of attacks that Islamic State fighters have launched against civilians in Afghanistan and Pakistan, including minority Shiite Muslims, as well as hundreds of clashes with Afghan, Pakistani and U.S.-led coalition forces since January 2017. Although the group has not yet attacked the U.S., the U.S. government considers it a threat to its interests and those of allies in South and Central Asia.

What is their role with the TALIBAN?

They are enemies. While intelligence officials believe al-Qaida fighters are integrated among the Taliban, the Taliban, by contrast, have waged major, coordinated offensives against the Islamic State group in Afghanistan. Taliban insurgents have sometimes joined forces with the U.S.-backed Afghan government forces to wipe out the Islamic State group from the northeast of Afghanistan.

An American Defense Department official spoke to The Associated Press under anonymity, saying that Trump had sought a 2020 withdrawal agreement with the Taliban in part to join forces against the Islamic State affiliate. That group was seen as a threat to America’s homeland by the administration.

What is the RISK NOW

Even when the United States had combat troops, aircraft and armed drones stationed on the ground in Afghanistan to monitor and strike the Islamic State, Islamic State militants were able to keep up attacks despite suffering thousands of casualties, Amira Jadoon and Andrew Mines note in a report for West Point’s Combating Terrorism Center.

The United States will lose its ground strike capability in Afghanistan and it could also be used to hamper its ability to track and deter the Islamic State and its attacks planning. Biden officials claim that the Islamic State group is just one of the many terrorist threats it faces globally. They claim they can manage it using so-called “over-the-horizon” military and intelligence assets, which are based in Gulf States on aircraft carriers or other distant locations.

The United States is concerned that Afghanistan, which has been under Taliban control for over 20 years, will become a base and magnet for extremists who plan to attack the West.

According to Jake Sullivan, U.S. national defense adviser, that threat was “something we’re focused upon, with every tool within our arsenal.”