The Post-Caliphate Terror Threat in Europe—and the Need for Continuing U.S. Assistance

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The Post-Caliphate Terror Threat in Europe—and the Need for Continuing U.S. Assistance

August 19, 2019 About an hour read Download Report
Robin Simcox
Robin Simcox
Former Margaret Thatcher Fellow
Robin Simcox specialized in terrorism and national security analysis as the Margaret Thatcher Fellow.


The Islamist threat to Europe has been reduced from its peak between late 2015 and fall 2017. Many of ISIS’ external operations planners have been killed, and no European plots in 2019 have thus far been directly tied to ISIS. However, the broader threat from ISIS is far from over. The post-caliphate center of gravity for jihadism remains unclear. There are a series of conflicts underway that could serve as magnets for foreign fighters fleeing the caliphate, and become a base for potential attacks in the West. There might not be one dominant theater, which would make the threat more complex and diverse. The U.S. must play a vital role in mitigating this threat. While the U.S. cannot, and should not, go it alone, it can work hand in glove with key European allies to strengthen collective security and prevent unnecessary duplication of efforts.

Key Takeaways

The Islamist threat to Europe has been reduced, with key ISIS external operations planners killed and its control of territory broken in Syria and Iraq.

However, the threat has diversified, and more terrorist attacks are still occurring in Europe than before the caliphate was established.

The next center of gravity for global jihadism is unclear. With conflicts simmering across the world, the U.S. and its allies must try to get ahead of the threat.

America’s strategy has worked: It took almost four-and-a-half years, but the Islamic State’s self-proclaimed caliphate in Syria and Iraq has been dismantled. The last remaining town under ISIS control, Baghouz in eastern Syria, fell to coalition and Syrian Democratic Forces in March 2019.

The destruction of the caliphate will make the world a safer place. It attracted foreign fighters, served as a training ground for a generation of terrorists, and breathed fresh life into key concepts in Islamist doctrine. Internal ISIS documentation laments a lack of suicide bomber volunteers, weaponry, and financing,REF with despondency and low morale among foreign fighters from Europe.REF Some (though by no means all) previously belligerent foreign fighters appear, at least on the surface, dejected and contrite in interviews with Western media.REF The foreign fighter flow to Syria has essentially ceased.

Yet the threat from ISIS is far from over. A United Nations Security Council report recently concluded that ISIS, “remains by far the most ambitious international terrorist group, and the one most likely to conduct a large-scale, complex attack in the near future.”REF

Increased focus is now being placed instead on the danger that ISIS is likely to pose as an insurgency. ISIS’ January 2019 suicide bombing in Manbij, in northern Syria, demonstrated that it is no idle fear. Four Americans were among those who lost their lives in that operation.REF As Alex Younger, head of the British foreign intelligence service MI6 warned, ISIS is “reorganizing and essentially returning to its natural state as an asymmetric transnational terrorist organization.”REF

While there was a degree of predictability about that, perhaps more uncertain is the impact that the loss of the caliphate will have on ISIS’ external terror operations. In Western Europe, there has been a steady pace of ISIS-inspired and ISIS-directed terrorist attacks over the past five years. In total, 1,749 people were injured and 371 were killed in Islamist plots between January 2014 and June 2019.

Removing ISIS from its caliphate appears to have had positive consequences for European security: As of mid-June 2019, there has not been a major, coordinated attack in Europe since fall 2017. However, more unsophisticated Islamist operations continue, with 21 injured and three killed in four separate attacks so far this year.

Pressure against Islamist groups must be maintained, and the U.S. must work hand in glove with European governments to counter their threat. The U.S. must help to ensure that no new safe havens for terrorism are able to emerge, helping build up the capacity of local partners in doing so. The U.S. should not condemn European approaches that take a tougher line on Islamism, such as the mooted U.K. policy to make it illegal to even travel to certain jihadism-impacted areas, while being firm in pointing out where improvements are still required. Furthermore, the U.S. must stay ahead of the threat as foreign fighters disperse to new conflicts simmering across the world.


While Islamist terror attacks have being occurring on European soil for over three decades, the frequency of plots has ebbed and flowed. This is no surprise: Such was the intricacy of some of al-Qaeda’s plans in the previous decade, they inevitably focused less on volume and more on impact—such as the 2006 plan to detonate liquid bombs on multiple aircrafts making transatlantic flights.

Following the so-called Arab Spring, al-Qaeda seemingly prioritized strengthening its hand in local conflicts. The amount of plotting in Europe was reflected by this: As late as 2013, the main terror attack in Europe was the stabbing to death of Drummer Lee Rigby in London by two men of Nigerian descent with British passports.REF Even here, al-Qaeda’s role was reduced to the ideological.

However, the number of plots in Europe would soon dramatically increase. There were several reasons behind this: The carnage in Syria, jihad becoming increasingly decentralized, the use of social media exploding, the caliphate arising, and ISIS being keener than al-Qaeda to focus on quantity of attacks over “quality.” The first attack by a foreign fighter—the murder of four people by Mehdi Nemmouche at the Jewish Museum in Brussels—occurred in May 2014, and there was a sharp uptick in the level of plotting from the summer of that year. This uptick was linked to the increasing intransigence of ISIS, which had just declared a caliphate and was increasingly focused on attacking Europe.

In 2015, the threat picture shifted dramatically. The al-Qaeda-approved Charlie Hebdo attack in Paris led to an ISIS-inspired follow-up attack on (primarily Jewish) civilians and the police, which occurred just hours later in the same city. Major ISIS-directed plots were thwarted (in Verviers, Belgium) or botched (in Villejuif, France, and on a train heading from Amsterdam to Paris). One was executed with devastating consequences: in Paris in November. The years that followed saw the threat level rise even higher.

Putting aside thwarted plots and a whole host of unsophisticated attacks, the following major terrorist incidents all took place between 2015 and 2017:

  • The attack on the offices of Charlie Hebdo in Paris (12 dead, 11 injured);
  • An attack on a policewoman and then on Jewish civilians at a supermarket in Paris (five dead, six injured);
  • Multiple suicide bombings and shootings throughout Paris (130 dead, 368 injured);
  • Multiple suicide bombings on Brussels transportation hubs (32 dead, around 300 injured);
  • A truck attack on a promenade in Nice (86 dead, 434 injured);
  • A truck attack on a Christmas market in Berlin (12 dead, 48 injured);
  • A car attack and then stabbing of a policeman near the Houses of Parliament in London (five dead, 50 injured);
  • A truck attack on a shopping district in Stockholm (five dead, 10 injured);
  • A suicide bombing at a pop concert in Manchester (22 dead, 116 injured);
  • A car attack and stabbing spree in London (seven dead, 48 injured);
  • A van attack at a promenade in Barcelona and car attack in Cambrils on the same day (16 dead, 137 injured); and
  • The bombing of a London Underground train (51 injured).

With the exception of the attack at Charlie Hebdo, all were directed, claimed, or inspired by ISIS.

By contrast, 2018 seemed almost like a respite. Not only were there fewer plots, the attacks that did take place were on a lower scale. The most high-impact was that by Radouane Lakdim in Carcassonne and Trèbes, in southern France, in March. Lakdim injured 15 and killed four (including civilians and police officers) in his ISIS-inspired attack.REF

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However, while not at the tempo of the 2015 to 2017 levels, the threat picture today is still more pronounced than it was before ISIS’ rise. Furthermore, even though the bloodshed has temporarily subsided, the terrorist threat continues to shape life in Europe in both small and significant ways: from anti-terror advertising campaigns in movie theatersREF to an increase in armed police or military on the streets and the construction of physical barriers throughout major cities.

What Made 2018 Different?

There were some similarities in 2018 to previous years.REF Each of the 10 countries targeted had been the subject of previous plots. France was the country most commonly targeted (consistent with the three years prior), with Germany and the U.K. also frequently plotted against. In addition, the trend of terrorists targeting members of the military and law enforcement (as well as civilians) continued.

Yet the differences were greater. First, the frequency of plots was less—an average of three a month, as opposed to, according to The Heritage Foundation’s internal dataset—seven a month, in both 2016 and 2017. Unusually, no 2018 plot in this dataset involved just the use of firearms as a weapon. There was a minimum of three in every other year and, as there have already been two solely firearm plots in the first six months of 2019, 2018 is likely to be an anomaly rather than a sign that terrorists are leaning away from firearms attacks. The number of edged-weapons plots in 2018 was half that of the previous year. There was also a significant reduction in explosives plots in 2018. On the other hand, there was an unusual amount of activity in the Netherlands, with five registered plots—a higher level of activity than in any other year.

There was evidence that terrorists and terror suspects were getting even more creative with their European plots in 2018, and the threat picture was growing more diverse.REF There were three chemical, biological, radiological, or nuclear (CBRN) terror plots in Europe in 2018—yet none from 2014 to 2017. All involved ricin, with one also involving anthrax. This should be no great surprise: According to one U.N. report, ISIS “retains an interest…in the use of chemical, biological, radiological and nuclear materials.”REF

While there have been other plots involving ricin in Europe in the past, 2018 was the first time it is alleged that it was successfully produced as part of an Islamist plot.REF Sief Allah H., a Tunisian asylum seeker who was in contact with ISIS, and Yasmin H., his German wife, were arrested in Cologne in June before they were able to execute their plan.REF The target was unclear, but they are alleged to have been planning to kill as many people as possible.REF They are also alleged to have tested the poison on a hamster prior to the plot’s disruption.REF

Also striking was an arrest made in the U.K. in the summer of 2018 to prevent an alleged plan to deploy drones as part of a broader Islamist plot. (The attack was also thought to involve edged weapons against law enforcement or military targets.)REF A U.N. report has highlighted the risk that ISIS’ “weaponization of commercial off-the-shelf drones” poses and stated that the group’s leadership “continues to procure such drones through a layered network of purchasers organized in small cells and spread across several countries.”REF This is an ongoing concern: Islamist plotters in contact with ISIS had previously suggested using drones as part of an attack against Israelis attending a soccer match in Albania in fall 2016.REF

Another unusual plot saw multiple attempts to derail trains in Germany. An Iraqi refugee and his associates are suspected of placing steel rope and cement blocks on train lines carrying high-speed trains. ISIS flags were found near the scene and the case is being treated as one of terrorism.REF Files discovered in Syria even hint at a potential link to ISIS’ senior leadership.REF

There were other quirks in 2018. In August, Salih Khater, a Sudanese-born Brit, drove a car into a group of civilians and the police outside the House of Commons, injuring three. It was treated as a terrorism case due to the target, method, and location. There was no claim of credit from ISIS—not unusual in and of itself, as the group often does not claim credit if the assailant is arrested (as opposed to being killed in the attack).REF Unusually, however, there was no electronic footprint linking Khater to extremism and he remained silent upon questioning by the police.REF

Days later, another unusual case involved Abdelouahab Taib, an Algerian who was shot dead by Spanish police after he yelled Allahu Akbar! and began to wield a knife in a police station. The attack was treated as a terrorist incident.REF However, Taib’s wife had recently discovered he was gay and it was theorized that his sense of shame led to carrying out an act that would lead to his death.REF

Finally, Mohammad A. R., a refugee from Syria, carried out an attack in Germany in October 2018. He tried to burn down a McDonald’s at the Cologne train station before taking a civilian hostage in a pharmacy. Mohammad A. R. said he was part of ISIS and demanded he be allowed to join the group in Syria, before being shot by police.REF While these events in and of themselves were not especially unusual, his age—55—was. Of 278 Islamist plots or attacks involving European targets that were studied between January 2014 and June 2019, only six (2 percent) featured those ages 50 and above.

Why Has the Threat Level Dipped?

The number of successful attacks has decreased each year since 2017. (It remains to be seen if this will remain the case by the end of 2019.) This is perhaps reason to believe that certain European countries have made some progress in improving their capacity to prevent terrorist attacks domestically.REF The same could also be said of the European Union more broadly, which has improved intelligence sharing, for example.REF

However, the amount of attempted attacks has also—at least for the time being—diminished since its peak from late 2015 to fall 2017. There are two key factors behind this.

Land and Manpower. Destroying the ISIS caliphate was a necessity. There was a clear need to prevent a further humanitarian catastrophe, particularly for religious minorities under threat from ISIS, as well as to restore territorial integrity to Iraq. (The situation in Syria remains more complex.)

However, and most pressingly from a Western security perspective, time and again terrorists have used their control of territory as a springboard from which to launch attacks overseas. Syria was no exception, with a wave of attacks in Europe originating from there, particularly from ISIS’ capital of Raqqa. There was little choice but to break ISIS’ control of this territory.

The fact that ISIS is now carrying out less-directed attacks is largely attributable to the military pressure placed on it by a U.S.-backed coalition and the shrinking of the territory from which to plan. This has played out in several ways. Most significantly, the U.S. and its allies have targeted specific ISIS members known to be planning external operations. This included “virtual” terrorist planners plotting against the West from the caliphate.REF A United Nations Security Council report concluded that “the fall in international attacks and plots has…been caused by attrition of key ISIL personnel.”REF

There are several examples. British intelligence concluded that two British citizens based in Syria, Reyaad Khan and Junaid Hussain, had used social media to plan attacks in the West “on an unprecedented scale.”REF This included plans to kill a U.S. Airman stationed in the U.K. and a plot to target VE Day celebrations and Armed Forces Day in May and June of 2015, respectively.REF Khan was killed in a U.K. drone strike in August 2015; Hussain, in a U.S. drone strike in the same month.

Another British citizen, Naweed Hussain, was killed in a U.S. drone strike in spring 2017.REF He had groomed young girls over Skype, marrying them over the Internet. One of these—Safaa Boular—was jailed for life after planning an attack in the U.K. at Hussain’s urging.REF

Similarly, a French jihadist called Rachid Kassim was connected to numerous plots in France before being killed in a missile strike in Iraq in February 2017.REF Then, between April 2018 and June 2018, a Danish intelligence official who defected to ISIS was killed along with two of his associates in air strikes, having plotted attacks in Sweden.REF

Others known to have used the caliphate as a base from which to help direct plotters in Europe include Tarik Jadaoun, a Belgian (sentenced to death by an Iraqi court in May 2018);REF and Lavrdim Muhaxheri, a Kosovo Albanian (killed in a Coalition airstrike in Syria in June 2017).REF

So far, no figures have emerged from within ISIS fill the vacuum—left particularly by Khan, Junaid Hussain, and Kassim—in terms of the frequency of plotting against the West. Taking several external operations planners off the battlefield has clearly led to a decline in ISIS activity on this front.

Other Europeans within ISIS who were tied to attacks in Europe have also been killed. These include Fabien Clain, a French citizen linked to ISIS’ coordinated attacks in Paris in November 2015, who was targeted in Syria in February 2019.REF It also includes Sammy Djedou, another French citizen based in Syria, who was integral to the planning and execution of those attacks, killed in a U.S. drone strike in Raqqa in December 2016.REF Another vital figure to ISIS’ operations in Europe was Abdelhamid Abaaoud, the ringleader of the Paris attacks. He was killed in a French police raid shortly after those attacks (although his broader network was able to strike in Brussels just months later).REF

There are a variety of other positive consequences to reclaiming territory from ISIS—consequences that put a dent in the group’s overall threat. A source of fundraising was diminished—ISIS made a significant amount of money from oil sales, taxation, and extortion from those living in its caliphate.REF ISIS’ military reverses are a likely contributing factor to the decline in their propaganda output from its 2015 peak, meaning it is not disseminating its messaging as far and as wide.REF Social media firms cracking down on extremist content have also helped in this regard.

Furthermore, the loss of physical territory accompanying a string of losses on the battlefield has likely made ISIS seem a less appealing group for potential new recruits to join and for less-ideologically committed pre-existing members to fight and die for. It is clear that the group lost much of the momentum it had built up—militarily and ideologically—in the period leading up to the caliphate’s declaration and the immediate aftermath.

However, there are caveats to this. First, as concluded in a U.N. Security Council report, if ISIS “regains access to permissive space and reinvests in external operational planning, a resurgence of directed attacks should be anticipated.”REF

Second, any internal despondency within ISIS does not automatically equate to the group being less dangerous. The Pentagon has been keen to play up the angle of low morale within ISIS since at least April 2016—yet it was still capable of pulling off some of its most devastating attacks to date in the months that followed.REF

Third, ISIS still has access to significant financial resources.REF The same U.N. Security Council report placed that figure as potentially being as high as $300 million and no lower than $50 million.REF To put that figure in context, the French government has assessed that ISIS’ November 2015 attacks in Paris cost approximately $90,000.REF

The Threat Today

Despite the progress made, there is ongoing concern about ISIS among Western officials, practitioners, and analysts alike. The only question is about the depth of the threat and where it will be directed.

There is a strain of thought that believes ISIS will turn its focus inwards. Hassan Hassan, co-author of ISIS: Inside the Army of Terror, has predicted that, post-caliphate, Islamist militants “will not focus on exporting violence to the West, but instead on infiltrating local communities and building influence. The future extremist landscape could be dominated by Hezbollah-like Sunni jihadist groups, ones that have the determination to fight a long war, but are grounded in local struggles.”REF This approach has some analogies to the approach currently taken by al-Qaeda.REF Ilan Berman from the American Foreign Policy Council also suggests the approach of an era of more localized jihad, with ISIS affiliates “unmoored from the ‘caliphate’ and…free to pursue their own, independent objectives.”REF

An optimistic reading of ISIS’ diminished capacity came from Edmund Fitton-Brown, Coordinator of the ISIL (Daesh)/Al-Qaida/Taliban Monitoring Team at the U.N., who has stated that “ISIL at the moment is not capable of directing complex international attacks” and any attacks are just “likely to be inspired” rather than directed. Fitton-Brown has stated that ISIS actually chose to wind up its external operations branch when it began to sustain battlefield losses in Syria and Iraq.REF

While there was certainly a decline in ISIS plots that were directed or funded from Syria since the 2015–2016 peak, Fitton-Brown’s conclusion seems too upbeat. Even when assessing just those numbers after ISIS’ last major attack in Europe in fall 2017, there were still 18 plots in Europe involving those who had some form of contact with ISIS.

ISIS has clearly not entirely abandoned this component of its operation. In 2018, for example, ISIS instructed Alagie Touray, a 21-year-old Gambian asylum seeker in Italy, to drive a vehicle into a crowd of people. Touray had allegedly recorded a pledge of allegiance to ISIS leader Abu Bakr al-Baghdadi in preparation for his attack.REF ISIS did the same with Lewis Ludlow in the U.K..REF And, as mentioned, ISIS was also in contact with ricin plotter Sief Allah H. in Germany.REF Then, in June 2019, it was revealed that a 16-year-old Bulgarian had been recruited online by ISIS to carry out an explosives attack in the southern city of Plovdiv. (This was the first publicly disclosed ISIS plot targeting Bulgaria.)REF

This helps explain the more cautious approach adopted in April 2019, when the head of Germany’s domestic intelligence agency stated that “I cannot give an all-clear on IS. It can launch an attack in Germany anytime.”REF Similarly, U.K. Counter Terrorism Policing’s Senior National Coordinator warned in June 2019 that “the U.K. is still facing an unprecedented level of threat from terrorism” and any recent dip in the amount of arrests was just terrorism-related activity returning to levels closer to what they were before a sharp 2017 uptick.REF

Furthermore, the U.N. Security Council report from early 2019 noted “the revival of links between individuals in various European countries” and ISIS’ leadership, fearing it could “re-establish an element of command and control.”REF Internal ISIS files discovered in Syria by The Sunday Times this year also showed some evidence that undercut the idea that ISIS lacked command and control capacity.

Included in these files was the correspondence from an Iraqi ISIS member called Abu Taher, writing to an ISIS leader in Syria, detailing that he “has individuals who want to work in areas far away from the Islamic State” and he had gained approval “for them to carry out the operations.” Abu Taher went on to request the establishment of a Bureau of Foreign Relations for the Department of Operations in Europe and stated that as long as the demands of his operatives on the ground in Europe were “realistic and reasonable,” ISIS would “meet all of their needs.”REF

Another file seen by The Sunday Times—from December 2018 and intended for Abu Bakr al-Baghdadi—detailed how ISIS’ external operations were the purview of a terrorist called Abu Khabab al-Muhajir, who was overseeing two cells in Germany and one in Russia. These cells were expected to provide money for the caliphate via bank robberies and to carry out vehicular attacks.REF Abu Taher also referred to an attack that would “destroy the economic world in Europe,” targeting an oil pipeline in Basel, Switzerland. This attack ultimately did not take place for unknown reasons. However, the evidence points toward ISIS being willing to strike in Europe once more if the opportunity arises.

There is also an ongoing risk from those angry at never making it to the caliphate before its destruction. That is not a new problem—“frustrated travelers” have been lashing out for years—but it is a persistent one. Dozens of plots and attacks in Europe have been launched by those who were thwarted in their attempts to travel to a conflict zone (usually Syria) since 2014.REF This includes Rakhmat Akilov, who carried out the truck attack in Stockholm in April 2017 after trying to travel to Syria.REF A major attack being planned in the Netherlands in September 2018 also saw the presence of frustrated travelers,REF while an individual who was prevented from traveling to Syria as a juvenile recently emerged as part of a plot targeting France in April 2019.REF

The Threat Tomorrow

Various factors are shaping the future terror threat.

Foreign Fighters: Plotters and Recruiters. There has been constant policy and academic focus on the threat posed by foreign ISIS fighters returning to Europe. This is understandable: Approximately 6,000 jihadists left Europe to fight in the Syria and Iraq conflict, and foreign fighters returning from Syria have carried out a series of terror attacks in Europe.

Many foreign fighters have been killed, and many others captured. Approximately 800 jihadists with European passports are now believed to be detained in Kurdish-run camps in Syria.REF European governments are reluctant to take them back, knowing that the inadequacy of their terrorism legislation means that these fighters will either receive very short sentences or, in many cases, not be prosecuted at all, and be right back on the streets of European countries. This unwillingness to take back citizens has been a source of ongoing frustration for the U.S., which does not want to be bogged down in Syria and wants to reduce the number of terrorists detained in ramshackle Kurdish camps.

However, some foreign fighters were never caught. As the caliphate began to collapse, smugglers transported ISIS fighters (both foreign and local) and their families to Turkey, where they were ordered to lie low. Some chose to enter (or re-enter) Europe, exploiting well-traveled migrant routes.REF European security officials have speculated that a host of other countries—ranging from Afghanistan to the Maldives—could serve as potential bases where foreign fighters can lie low after the loss of the caliphate.

So the foreign-fighter terror threat will be an ongoing one. However, while not all foreign-fighter returnees may plan new attacks, even those who do not do so present a potential security threat. After all, there are tens of thousands of other radicals in Europe for them to connect with upon return, and those foreign fighters who fought in previous foreign conflicts—such as Afghanistan in the 1980s and Bosnia in the 1990s—returned with an enhanced reputation as fearsome warriors within the mujahideen. Some turned into recruiters for future conflicts.

For example, a British citizen, Babar Ahmad, leveraged his experience fighting in Bosnia in the 1990s to become one of the most prolific recruiters for terrorist causes in the U.K. Part of this took place online: Ahmad was considered the “godfather” of Internet jihad, a pioneer in using the Internet to spread the violent Islamist message and provide updates on the conflicts then occurring in Chechnya and Afghanistan.REF

Ahmad also ran study circles in South London. One of his disciples was Saajid Badat, a young British citizen who was drawn into Ahmad’s orbit and then dispatched to Afghanistan to train with al-Qaeda.REF Badat was assigned by al-Qaeda to be part of the same December 2001 suicide bombing mission as “shoe bomber” Richard Reid. While Badat ultimately did not go through with the attack, withdrawing at the last moment, he did plead guilty in a U.K. court concerning his role in 2005. For his part, Ahmad pleaded guilty to terrorism offenses in the United States in 2013 following a lengthy extradition battle.

While the legacy of the caliphate and the conflict in Syria is still being written in jihadist circles, it may well have even greater luster attached to it than Bosnia in years to come. It must be anticipated that returnee foreign fighters will use past ISIS “glories” to recruit a new generation to the Islamist cause.

Children. Entire families, including very young children, from the West moved to Syria to live in the ISIS caliphate. There have also been children born in Syria to parents who are citizens of Western countries. Many of these children will be deeply traumatized, and many will have been exposed to ISIS doctrine. Europol has warned that ISIS propaganda “repeatedly depicted the training and indoctrination of minors,”REF and multiple videos have emerged of children brutally executing detainees in ISIS-controlled areas.REF ISIS is also known to have deployed children in military operations in Iraq and Syria.REF Europol has assessed that ISIS members “train these minors to become the next generation of foreign terrorist fighters” and that this “may pose a future security threat.”REF

There are likely hundreds or even thousands of children in Syria with links to Europe, although the precise number that will eventually return, or are even eligible to return, is still unclear.REF Proving their nationality will not always be simple, as identification papers could be lost, or have been issued by ISIS and, subsequently, not recognized by European countries. Proving paternity may also not be easy, especially for children of rape victims.REF Some are orphaned, others are still with their parents in the Kurdish-run camps in Syria.

While many countries are reluctant to lobby for the repatriation of adults, France, the Netherlands, and Belgium have begun to take back some orphaned children from the camps in Syria.REF As French Minister for the Armed Forces Florence Parly said when discussing child returnees from the caliphate, “the challenge for us is to turn them into citizens again.”REF It is a daunting task.

The Known Unknown. Predicting how the threat will metastasize is close to impossible. Furthermore, Islamist terrorists have consistently surprised analysts and policymakers. From 9/11 to the Easter 2019 church bombings in Sri Lanka, the resilience and capacity of Islamist terrorists has consistently been underestimated. With this in mind, there are a series of conflicts underway that could serve as a hub for potential attacks into the West and serve as magnets for foreign fighters fleeing the former caliphate.

In the Middle East, Syria remains an ongoing concern. Navigating the morass of Syrian rebel groups and their fluid loyalties can be challenging, but, at the very minimum, forces recently aligned with al-Qaeda have control of territory in Idlib, Syria. ISIS also remains a potent force in Syria, still attempting to regain territory it once held, such as Palymra, from the Assad regime.REF Al-Qaeda and ISIS both operate in Yemen, although any publicly disclosed evidence that their current priority is attacking the West, as opposed to spreading its influence locally, is hard to come by. However, with war ongoing and territory still contested, the opportunities for both to expand their presence and bolster their ranks remain.

There is increased concern about Southeast Asia as fertile ground for recruitment and terrorist travel. The territory ISIS controlled in Marawi in the Philippines was wrested from it, yet it continues to carry out bombings of churches there. ISIS has previously launched deadly attacks in Jakarta, Indonesia, and also targeted Malaysia.REF Ongoing persecution of Muslims in Myanmar also presents opportunities for Islamist recruitment.

In South Asia, the future of Afghanistan, where the U.S. is attempting to negotiate a peace deal with the Taliban, and where ISIS and al-Qaeda retain a significant presence, is contested. Directly to the north, two Americans were among those killed in Tajikistan by terrorists who had pledged their allegiance to Abu Bakr al-Baghdadi.REF The Easter terror attacks in Sri Lanka were carried out by Islamists inspired by ISIS, and there have been multiple thwarted plots in the Maldives.REF Al-Qaeda in the Indian Subcontinent (AQIS) also appears to be an increasingly relevant regional outfit, although al-Qaeda recently used a U.K. recruit, not to plan attacks in Europe, but to use Delhi as a base to recruit for the cause in Kashmir and Myanmar.REF This suggests that, for the time being, AQIS also prefers to pursue a localized strategy, which al-Qaeda’s senior leadership has deployed in other parts of the world.

In West Africa, the Islamic State in Greater Sahara (ISGS) is one of ISIS’ most active affiliates, and Abu Bakr al-Baghdadi made several references to African nations in a 2019 ISIS video.REF The British government has become so concerned about the region that it is considering whether to make it an offense for British nationals to travel to certain parts of West Africa at all (as well as Syria).REF

Yet it is not just West Africa where there is a problem: ISIS also recently claimed credit for attacks in Mozambique and the Congo,REF and the U.S. has pounded al-Shabaab, al-Qaeda’s Somali affiliate, with an unprecedented number of drone strikes.REF Meanwhile, al-Qaeda in the Islamic Maghreb (AQIM) continues to operate in the Sahel, with its Sahara branch merging with other al-Qaeda linked organizations to form the Group for Support of Islam and Muslims (JNIM), an outfit loyal to al-Qaeda emir Ayman al-Zawahiri.REF

Even outside AQIM’s activities, North Africa remains blighted by the activities of jihadist groups. Libya remains an ongoing concern with the Manchester suicide bomber, Salman Abedi, known to have met with ISIS fighters there prior to his attack in May 2017.REF In Morocco, two Danish tourists were brutally murdered by ISIS-inspired terrorists in December 2018;REF while nearly 3,000 Tunisians successfully journeyed to Syria and Iraq to participate in the fighting there.REF

All of this may be relevant to how the threat develops; or perhaps none of it will be. For example, perhaps European foreign fighters will find Syria both accessible and Manichaean in a way that jihad in other countries is not. The jihadi world is likely in flux after the end of the Caliphate, as uncertain as U.S. and European policymakers are as to where the center of gravity will lie next. This heightens the need for the U.S. and its allies to be vigilant, watch contours within the jihadist movement carefully, and try and get ahead of the threat if possible.

The Importance of Continuing U.S. Engagement

European countries can take credit for cracking down on terrorist activity. However, the enduring importance of the U.S. in mitigating the threat cannot be forgotten.

It was U.S. diplomacy that helped form the Coalition to defeat ISIS in Syria and Iraq. It was U.S. hard power that helped break the territorial control of the caliphate. It was the U.S. military that took many of the key Europeans planning attacks off the battlefield via drone strikes. The U.S. Treasury has worked to shut down ISIS’ funding.REF U.S. intelligence helps thwart plots targeting Europe.

The U.S. intelligence community also helps keep information flowing within European countries. Certain European countries legally struggle to share intelligence between their law enforcement and intelligence communities. As convoluted as this process may be, the U.S. serves as a trusted interlocutor to ensure that information gets to the right agency within a given country.REF

Therefore, Europe has every motivation to keep the U.S. engaged. The U.S. cannot, and should not, go it alone, and each of these tactical victories involved the U.S. working closely with partners, either bilaterally or multilaterally. Sometimes the U.S. will not be in the lead. The French intervention in Mali, which took place with U.S. technical support, was a successful example of how good collaboration should look. Collaborating this way also prevents unnecessary duplication of efforts.REF

This is an approach that European governments must seek to build upon. They can do so by demonstrating that they are serious about their own security while retaining and, where appropriate, stepping up their contributions to counterterrorism initiatives around the globe.

Recommendations for the U.S.

In order to help prevent ISIS from posing the threat to Europe that it did between 2015 and 2017, the U.S. should:

  • Ensure that there are no new safe havens for terrorism. Preventing the emergence of territory governed by terrorists has been an integral part of the West’s post-9/11 posture and should continue to be so. The U.S. must stay engaged militarily in Afghanistan and Syria, hubs of potential threats to the West, while providing support to key allies and partners to prevent new safe havens from emerging in other threatened regions.
  • Maintain support for local partners in their areas of influence. The U.S. cannot defeat terrorist groups alone, nor should it be expected to. However, it can play a vital role in backing appropriate partners—whether financially, or with training and technical support—in Islamist-imperiled regions in order to contain the threat. While these partners will rarely be perfect, the U.S. should help them develop their capacity in order to prevent the threat from metastasizing and becoming an imminent threat to U.S. interests.
  • Respect European security concerns. The U.S. desire for Europeans to take their foreign fighters back is understandable. However, European countries are in a difficult situation: Accepting back hardened terrorists without much prospect of successful prosecution is an unappealing offer for any government. The U.S. could encourage certain European governments to develop alternatives to prosecution—such as the Peace Bond system in Canada or the Terrorism Prevention and Investigative Measures in the U.K.—that place certain restrictions on the freedom of terror suspects who cannot be prosecuted.
  • Refrain from calling out those European countries that do take a tougher line on Islamists, even when it is not an approach shared by the U.S. While European countries have been far too lax on Islamism historically, some countries have now taken tougher approaches that have proven controversial: The U.K. has revoked British citizenship of dual nationals that pose a security threat and is attempting to prevent any of its citizens from traveling to certain countries and regions. Hungary and Italy have taken a restrictive approach on migration policy, trying to avoid the enclaves, radicalization, and violent crime that countries with a far more open approach to asylum, such as Sweden and Germany, have.REF As long as European countries are showing a willingness to take the Islamist problem more seriously, while remaining cognizant of the need to respect human rights, the U.S. should be willing to give them fairly wide latitude.
  • Be firm in telling European governments where improvements are needed. While European countries have made some progress in bolstering internal security, including in tightening legislation that will make it easier to prosecute foreign fighters in the future, there is still much to do. The U.S. can encourage more defense spending, continue to encourage the improvement of intelligence sharing—especially on potential future threats, as opposed to known active ones—and the prevention of radicalization in prisons.
  • Help European governments to develop policies for the integration of children from ISIS-controlled territory. Integrating children into Europe, after their non-integrated parents chose to live in the caliphate, is a major challenge for several governments. In some cases, domestic prosecutors may consider it in the public interest to bring charges and detain minors in juvenile detention if they are shown to have committed crimes, are above the age of criminal responsibility, and still pose a risk. Generally, however, the focus should be on trying to integrate children indoctrinated with ISIS’ ideology into Western society. Getting children to engage with social workers, youth-offender services, and psychologists should be a priority. The state must also ensure that orphans, and perhaps other children, can be placed in foster homes.
  • Resist proclaiming a premature victory over ISIS. Such a move only invites complacency. The ISIS caliphate is gone, but European countries face internal Islamist threats, and must be encouraged to address them much more aggressively and consistently. While declarations of victory are tempting, the Islamist threat is generational and beyond the ability of any one Administration to resolve.


The security situation in Europe has been so perilous in recent years that good news must be acknowledged whenever it arises. The ISIS caliphate has been defeated, ISIS’s momentum has been dented, and there are not as many Islamist attacks now as there were in previous years. In short: Fewer people are dying.

However, this progress must be put in context. Despite the very recent reduction, there is still more terrorist activity than there was even just five years ago, let alone at the start of the decade. Even as late as 2014, despite the declaration of the caliphate that June, only two plots that year led to any deaths or injuries.REF Such numbers now look quaint by comparison: At the time of this writing, there have already been four attacks in Europe in 2019.

Continuous vigilance is required. In all likelihood, ISIS will continue to rely on low-cost, high-impact plots using knives and vehicles in the short term, while planning more intricate and complex ways of attacking Europe in the future.

Furthermore, the post-caliphate center of gravity is still unclear. It may be that there is not one dominant theater, like the one Syria became, but that the threat becomes more complex and more diverse, with different conflicts appealing to different constituencies. Either way, Europe will remain a fundamental target for jihadist groups, and the U.S. must remain an indispensable ally in helping Europe cope with whatever comes next.

Robin Simcox is the Margaret Thatcher Fellow in the Margaret Thatcher Center for Freedom, of the Kathryn and Shelby Cullom Davis Institute for National Security and Foreign Policy, at The Heritage Foundation.


Robin Simcox
Robin Simcox

Former Margaret Thatcher Fellow