The New Orleans mass killing put a spotlight back on ISIS, which never really went away

• The New Orleans attack suspect carried an ISIS flag and pledged fealty to the group, officials said.
• The group, best known for global mass killings in 2015-2017, has again been gathering strength.
• The group was damaged but not defeated by a US-led campaign.

Back in 2017, the ISIS militant group's reign of terror appeared to be coming to an end.

A US-led coalition ousted its fighters from strongholds in Iraq and Syria, where they had ruled with brutality and inspired a series of harrowing attacks on Western cities.

The loss of its bases and the assassination of many of its leaders badly dented its power, and its prominence faded.

The attack in New Orleans on Wednesday brought the group back into stark prominence.

Fifteen people were killed when the driver of a truck slammed into New Year crowds on Bourbon Street — authorities said the suspect pledged allegiance to ISIS and flew its flag.

Experts and security officials have in recent months issued increasingly urgent warnings of ISIS gathering strength.

ISIS has "remained a continuing threat," said Jessica White, a terrorism analyst at London's Royal United Services Institute, even though it "had to adapt after its territorial defeat."

"They are a diffuse and networked organisation that has alliances and branches that continue to wield influence, cause terror, and further their goals," she told Business Insider on Thursday.

The FBI said it is investigating what ties the suspect, Shamsud-Din Jabbar, may have had with the group. Authorities have said Jabbar did not act alone and are seeking more information on any associates.

ISIS renews itself

ISIS was little-known in 2015, when it shocked the world by seizing swaths of Syria and Iraq and putting them under a severe form of Islamic law.

The group became known for atrocities, staging theatrical beheadings of hostages, seizing thousands as slaves, and orchestrating waves of terror attacks.

Its adherents cumulatively killed hundreds of people in attacks on Western cities, including Paris and San Bernardino in 2015, Berlin, Brussels, Nice, and Orlando in 2016, and London and Barcelona in 2017.

Attacks in Iraq, Yemen, Pakistan, Afghanistan, and Saudi Arabia killed many hundreds more.

A US-led military response, launched under President Barack Obama and continued under President Donald Trump, gradually eroded the group with airstrikes supported by allied militias on the ground. 

It culminated with the assassination of its leader, Abu Bakr al-Baghdadi, by US special forces in 2019.

Trump has since boasted of destroying the group, claiming at last year's Republican National Convention that in his first term "we defeated 100% of ISIS."

Since then, the US has maintained a small military presence in northern Syria meant to monitor and extinguish potential resurgence by the group.

Analysts say the group has seized on instability in Afghanistan, where the Taliban regained power after the 2021 US withdrawal, and ongoing chaos in Syria to quietly rebuild its strength.

The group's Afghan affiliate, ISIS-K, presents a particularly potent threat, wrote Colin Clarke, Director of Policy and Research at The Soufan Group, for Foreign Policy in August.

"It is both pushing its propaganda to a more global audience and threatening attacks farther afield," he wrote.

ISIS-K was linked to the March 2024 attack on a music venue in Moscow where 145 people were killed, as well as an attack on a procession in Kerman, Iran, in January 2024 where 95 were killed.

In August, officials foiled a planned ISIS attack at a Taylor Swift concert in Vienna, Austria. The CIA's deputy director said extremists planned to kill "a huge number" there. 

Tactics to spread terror 

One of the main challenges for investigators will be to establish whether the New Orleans attacker took direct instruction from ISIS or was acting on his own volition, Sajjan J. Gohel, International Security Director at the Asia-Pacific Foundation, told CNN. 

The group mostly does not directly train extremists at its bases to carry out attacks, unlike the terror group Al-Qaida.

Instead, it largely remotely recruits and directs followers to carry out attacks that don't require much training, such as vehicle ramming or knife attacks.

Clarke, the ISIS expert, described this approach in his August article, called it a "virtual entrepreneur" model.

"Operatives in Afghanistan or Pakistan make contact with would-be ISIS-K supporters abroad to try to convince them to carry out attacks in the countries where they reside," wrote Clarke. 

Attacks following that model include the 2016 beheading of a Catholic priest in a church in France, according to reports at the time. 

The group is now less concerned with recruiting members in Syria and Iraq, and more on inciting attacks, said White, the RUSI expert.

"While the focus has shifted away from gathering followers to a centralised physical Caliphate, this has transformed the messaging to encouraging devotees to commit attacks whenever, wherever, and by whatever means they can," she said.

The New Orleans attack had "several strategic and symbolic considerations as potentially textbook ISIS," Gohel said.

Vehicle-rammings have been a feature of many deadly, ISIS-linked attacks.

The group's sophisticated propaganda is another powerful tool, enabling it to exploit grievances and attract supporters anywhere where there is internet access.

In some cases, followers with no direct links to the group have carried out attacks in its name. The 2017 Westminster Bridge attack in London seemed to fit that pattern.

The group's use of the internet, and success in radicalising those with no previous extremist links, make it particularly difficult to tackle.

"None of this is new. They just continue to throw it out every single day," Aaron Zelin, an expert on jihadist groups at the Washington Institute for Near East Policy, told NBC News of the group's methods. "And from their perspective, the hope is that it sticks with somebody,"