‘WE killed the last murderous bastard who ran IS, let’s go get the next one.”

These were the tough-talking words of US Republican Senator Ben Sasse of Nebraska a few days ago, following news that Islamic State (IS) leader Abu Bakr al-Baghdadi had been killed by US Special Forces in north-western Syria last week. Sasse’s remarks were very much in keeping with the kind of gung-ho, knee jerk response we have come to expect from the administration of US President Donald Trump.

Indeed, listening to Trump in the wake of the raid to kill al-Baghdadi, one could have been forgiven for thinking that it was “mission accomplished” and IS was now a spent force.

But both Trump and Sasse’s responses belie the reality of what remains a formidable challenge when it comes to tackling the terrorist threat posed by IS. For its part the jihadist group wasted no time in announcing a successor to al-Baghdadi in the shape of someone called Abu Ibrahim al-Hashemi al-Qurashi.

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Not to be outdone, Trump on Friday, in typical grandstanding style, equally wasted no time in tweeting: “ISIS has a new leader. We know exactly who he is!” The president however did not elaborate, probably because the reality again is more than likely rather different.

For besides being a name that implies the new leader is a descendant of the Qurashi tribe of the Prophet Muhammad, counter terrorism experts almost universally admit they know next to nothing about him.

“Nobody – and I mean nobody – outside a likely very small circle within IS have any idea who their new leader ‘Abu Ibrahim al-Hashemi al-Qurashi’ is,” Paul Cruickshank, of the US-based Combating Terrorism Centre, tweeted in response to IS’s eight-minute-long audio recorded announcement posted on messaging service Telegram.

That there should be a lack of any biographical details is however of no surprise says Rita Katz, director of the SITE Intelligence Group, which tracks online networks affiliated with jihadist organisations.

“Any successor that is already known to the world would start his rule with a major security vulnerability,” Katz told Time Magazine.

“I don’t foresee a video message, audio message, or anything that is in any way revealing,” Katz added.

If analysts are agreed on one thing too, it’s that the list of potential successors to al-Baghdadi appears to be short. According to Hisham al-Hashimi, an Iraqi expert on IS, two potential candidates stand out.

The first is Abu Othman al-Tunsi and the second Abu Saleh al-Juzrawi, who several leaked internal IS documents also referred to as Hajj Abdullah. While al-Tunsi is a Tunisian national who heads IS’s Shura Council, a legislative and consultative body, Abdullah is a Saudi who runs the group’s so-called Delegated Committee, an executive body.

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In the tangle of names that has become a hallmark in trying to identify IS leaders, analysts say that the officially announced new leader, al-Qurashi, may yet again be another nom de guerre for Abdullah, who has previously been identified as a likely successor to al-Baghdadi.

But both these potential Tunisian and Saudi options, the Iraqi expert al-Hashimi told French news agency AFP, would likely be controversial because neither is a Syrian or Iraqi national, who make up the bulk of IS’s landless fighting force.

Whoever al-Qurashi is, he will inherit the challenging task of leading a fractured organisation that in many cases has been reduced to scattered sleeper cells, albeit one that remains a real threat.

While the death of al-Baghdadi will undoubtedly have further damaged the organisational and strategic capacity of an already beleaguered IS, past evidence suggests that it will not significantly undermine the popularity of al-Baghdadi’s extremist ideas.

Back in 2011, the death of al-Qaeda head Osama bin Laden sparked a debate about whether his death might help lessen the appeal of his ideas or inadvertently make them more popular than ever. Writing back then, the well-known Arab commentator Abdel Bari Atwan warned of the “danger that post-Bin Laden, al-Qaeda may emerge even more radical, and more closely united under the banner of an iconic martyr”.

But others argued that rather than make him a martyr, bin Laden’s killing demonstrated that he was, like the rest of us, mortal.

That same debate now exists in some quarters following the death of al-Baghdadi. But in its announcement on Thursday IS made clear that it saw al-Baghdadi and former IS spokesman Abu al-Hassan al-Muhajir, who was killed in an airstrike days later, both as “martyrs”.

The jihadists warned too against rejoicing in al-Baghdadi’s death. In the recording posted on messaging service Telegram, IS’s new spokesman warned the US to “beware vengeance” for al-Baghdadi’s death, while also mocking Trump’s erratic leadership and reminding the world of the group’s global reach.

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Right now it would be all too easy to write off IS’s presence in Syria and Iraq as nothing more than the ghostly legacy of al-Baghdadi.

In the time I’ve spent in both countries covering the battle against the jihadist group, the tangible evidence of their previous and current presence is certainly everywhere. From the tunnels and booby traps in cities like Mosul and Raqqa to the mass graves and thousands of faceless, black-clad female followers haunting refugee camps, IS’s presence remains palpable. While many of their fighters may now languish in prisons, thousands more are still at large regrouping and organising.

It’s estimated that IS still has as many as 18,000 fighters in the region with 3000 foreigners among them. While many are in sleeper cells or operating semi-autonomously, this current fragmentation or de-centralisation of IS may only turn out to be bad news instead of good after al-Baghdadi’s death.

In the absence of a prominent personality like him, what’s left is ideology. IS is considered the most extreme group in the jihadist sphere, but its basic ideology is only marginally different from al-Qaeda’s, even though that difference was important enough to precipitate a split between the two in 2014.

Now however, with the IS territorial caliphate in ruins, the ideological space between the two groups has narrowed. For some time now there has been evidence of IS fighters returning to areas in Syria, where al Qaeda-affiliated groups still operate. Indeed al-Baghdadi, much to the surprise of many IS watchers, was holed up in the house of Abu Mohammed Salama, a commander of Hurras al-Din, a jihadist group considered loyal to al-Qaeda chief Ayman al-Zawahiri.

Al-Baghdadi was not the first or likely the last IS member to seek sanctuary in the backyard of their old-time rivals. The signs have been there for some time.

Earlier this year, during a brief ceasefire in Baghouz village in north-eastern Syria, where IS made its last territorial stand, one solution proposed by IS to end the fighting was safe passage for its 300 or so fighters to Idlib, home to Hurras al Din, affiliate of al-Qaeda.

And therein in the eyes of many counter-terrorism experts lies the nightmare scenario, a world in which al-Qaeda and IS affiliates across the globe join forces and start sharing resources. Certainly there remains a lot of bad blood between the two. To this day, al-Qaeda leader al-Zawahiri’s speeches rarely come without some critique of the “epidemic” put forth by IS, branding the group too extreme and ultimately harmful to the jihadist cause.

Forever tactically more astute and differences aside, al-Qaeda though has now been given its biggest opportunity yet to bring IS cadres back into its fold, say many observers.

“The rump of the Islamic State in Iraq and Syria might ally itself again with al-Qaeda, despite their public, hostile divorce in 2014,” says renowned terrorism and counter-terrorism analyst Bruce Hoffman of the US- based Council on Foreign Relations (CFR).

“Should the Islamic State’s branches in Africa and South Asia follow suit, the West would face a renewed and perhaps even greater global terrorist threat,” Hoffman warns, pointing to several factors to support this possibility.

The first is that the two organisations share similar ideologies, with their differences being more a product of a clash of their leaders’ egos than of differences in core beliefs.

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The second is that IS’s once compelling attraction to foreign fighters and home-grown recruits is now likely to atrophy, if not reverse. But perhaps above all else, says Hoffman, al-Qaeda is keen to acquire IS’s sophisticated social media skills and its ability to strike in places as far as Western Europe and South Asia.

With Islamist-inspired terrorist plots in the UK and Europe still directed from the Middle East by IS supporters, British intelligence agencies are heightening their monitoring of subjects of interest after the death of al-Baghdadi.

Although the main fear remains lone actors who may not be on the security services’ watch list, IS still has a considerable online capacity that wields singificant influence. Speaking a few days ago, former Nato commander and retired US admiral James Stavridis warned that IS will likely accelerate planned attacks after the death of al-Baghdadi and may again look to target Christmas markets in their assault.

“IS is not a single individual, unfortunately. If it were, this would be over. It’s not. Just like winter is coming, the Islamic State is coming back,” said Stavridis.

In the UK the response by the security services covers about 3000 people here and abroad who are believed by MI5 to have connections to IS or who could be inspired by the group to launch terrorist attacks in Britain.

Whatever IS’s capacity to operate globally, back in its own backyard of the Middle East popular anger is again creating the ideal conditions in which the jihadists thrive and will doubtless seek to exploit.

As an opinion piece in the Washington Post a few days ago pointed out, while Trump in his speech clearly sought to dance on the grave of al-Baghdadi following the US raid, the President’s time “might have been better spent reflecting on the circumstances that facilitated al-Baghdadi’s rise in the first place, circumstances that are now driving a surge in protests around the Middle East”.

From al-Baghdadi’s homeland of Iraq across Lebanon and Egypt there is unrest that risks repeating the cycle of chaos that brought IS to power in the aftermath of the 2011 Arab Spring.

Other factors too that enable the jihadists to flourish continue to plague the region and remain dangerously unaddressed. The marginalisation of Sunni Muslims in some areas of Iraq for example, or the failure to invest and rebuild in areas previously “liberated” from IS and the heavy hand of Shiite militias have all helped facilitate disgruntlement in some Sunni communities that IS have in the past and are showing signs again of harnessing to their advantage.

Time and again in the wake of IS being ousted from major Iraqi cities like Mosul there were warnings that government failure to help Sunnis rebuild their lives was likely to have long-term consequences for the country’s stability and security.

How telling it is that perhaps more than anywhere else in the region right now, it’s precisely in these communities that IS once again is making its presence felt, and will continue to do so even without al-Baghdadi as leader.

“You cannot fight terrorism just by fighting terrorism, and to think that you can is an illusion that has long hobbled US policy in the Middle East and South Asia,” pointed out Shadi Hamid, a senior fellow at the Project on US Relations with the Islamic World at the Brookings Institution, last week.

“The killing of al-Baghdadi is no doubt a success, but self-congratulation will take us only so far and not nearly far enough,” warned Hamid, writing in the influential current affairs magazine The Atlantic.

Those hawks within the Trump administration like US Republican Senator Ben Sasse can implore all they like about going out to “get the next one”. But there will always be another leader prepared to take up where al-Baghdadi and others left off.

Wielding the big stick in the fight against terrorism is only one small part of the answer in defeating its toxic appeal.