In the immediate aftermath of 9/11, the United States’ resolve was clear: never again. Never again would it let shadowy networks of jihadists, acting in the name of a perverted version of Islam, carry out a catastrophic attack on American soil. And so, in fits and starts, the George W. Bush administration and then the Obama administration developed a strategy for fighting what became known as “the global war on terror.” Washington sought to disrupt plots wherever they emerged and deny terrorists safe havens wherever they existed. When possible, it would rely on local partners to prosecute the fight. But when necessary, it would act alone to disrupt plots and kill or capture terrorist operatives and leaders, including with drone strikes and daring special operations raids such as the one that killed Osama bin Laden.

Today, the terrorist threat looks much different than it did right before 9/11. The U.S. counterterrorism community has dramatically ramped up its intelligence capabilities. Determined to “connect the dots” in the future, the U.S. government created new agencies and instituted a new paradigm for intelligence—share by rule, withhold by exception—and set up a slew of “fusion centers” and joint task forces to foster interagency cooperation. Borders were hardened, cockpit doors reinforced, and watch lists created. In Afghanistan, the United States overthrew the Taliban regime, which was hosting al Qaeda. Today, despite recent Taliban gains, al Qaeda still does not enjoy free rein in the country. In Iraq and Syria, al Qaeda’s offshoot, the Islamic State (or ISIS), is on the run, thanks to the work of a global coalition assembled in 2014 and U.S.-led air strikes and special operations raids. The group’s Iraqi capital of Mosul fell in July, and its Syrian stronghold in Raqqa is almost certain to follow. Owing to the relentless pressure that the United States and its allies have placed on terrorists’ safe havens, the threat of a complex and catastrophic attack emanating from abroad—although not gone—has diminished.

At the same time, however, the threat from homegrown and so called lone-wolf terrorism has increased. This kind of terrorism is not new, nor is it confined to Islamic terrorism (in fact, according to one study by the FBI and the Department of Homeland Security, from 2000 to 2016, white supremacists killed more people in the United States than any other group of domestic extremists). But these threats have taken on new urgency as ISIS in particular has harnessed the power of social media to inspire mostly young men to commit violence. In 2014, Abu Muhammad al-Adnani, ISIS’ now deceased media spokesperson, urged followers to be resourceful when confronted with the opportunity to murder an unbeliever: “Kill him in any manner or way however it may be: smash his head with a rock, or slaughter him with a knife, or run him over with your car.”

People were listening: one study, by Lorenzo Vidino, Francesco Marone, and Eva Entenmann, identified 51 attacks between June 2014 and June 2017 by terrorists who had heeded the call to act locally in Europe and North America, with 16 of those carried out in the United States. The 2016 mass shooting in Orlando and bombings in New York City and New Jersey likely resulted from a mix of jihadist inspirations, but in both cases, the killers had no known external direction or training. The common theme: consuming a variety of extremist content online. A threat that began with an attack planned by a small group of veteran terrorists in Afghanistan has transformed into a diffuse movement of recently radicalized individuals planning pop-up attacks across the globe.

What is the right strategy for this new phase of the war on terrorism? The answer is one that confronts three main challenges: physical safe havens from which terrorists continue to plot attacks, virtual safe havens through which ISIS and other groups mobilize individuals to commit violence, and a global and domestic environment increasingly hospitable to terrorists.

A SWAT team hunts for the Boston Marathon bombers shortly after their attack, April 2013
Jessica Rinaldi / Reuters


Although the likelihood of another 9/11 has diminished, it is far from zero. Indeed, it appears that al Qaeda is passing the mantle to a new generation, with bin Laden’s son Hamza releasing several audio recordings since 2015 calling on followers to commit violence. Moreover, the group’s various offshoots are busy plotting attacks. The most dangerous elements of its largest affiliate, Jabhat al-Nusra—more accurately described as al Qaeda in Syria—are still intent on attacking the United States. So is al Qaeda in the Arabian Peninsula, or AQAP, al Qaeda’s Yemeni affiliate, which has proved persistently focused on attacking airliners.

ISIS, for its part, faces almost certain defeat in Iraq and Syria, but it seeks to sustain its brand with no fewer than eight global branches, from Afghanistan to Libya. And it has not been satisfied with merely amassing territory. Its affiliate in Egypt’s Sinai Peninsula brought down a Russian passenger plane in 2015. And in August 2017, Australian police announced that they had foiled a sophisticated plot by ISIS to blow up a passenger jet. In separate shipments, an ISIS commander in Syria had sent followers in Sydney the parts for an explosive device that could be assembled in country—an approach that the analyst Paul Cruickshank has called “an IKEA model of terror.” Although authorities have said that airport screening would have detected the device, ISIS is testing ways to defeat such defenses, and it’s easy to imagine it succeeding. The lesson here is that the United States cannot take its eye off the threat of a massive, sophisticated attack.

One of the most reliable strategies for preventing such attacks has been depriving terrorist groups of the ungoverned spaces they use to train and plan, from Afghanistan to North Africa. Although territory is no longer the sine qua non it once was—the rise of virtual safe havens and encrypted communications has given terrorists new ways to covertly plan attacks—there is still no substitute for it. Physical territory not only provides terrorists with room to plot but also offers reliable revenue from taxation and, often, oil sales, as well as human resources through forced conscription. And so the United States must continue to put relentless pressure on safe havens.

In practice, especially as the wars in Afghanistan and Iraq have wound down, this has meant adopting a “light footprint” counterterrorism strategy, premised on training and enabling local partners to take the fight to terrorists and, failing that, doing so directly through air strikes (both manned and unmanned) and special operations raids. This strategy has been successful at eliminating dangerous operatives, but it has had its downsides. At times, U.S. air and ground operations have generated backlash among locals, and unfortunate instances of civilian casualties from these operations have further fueled terrorists’ propaganda and recruitment efforts.

U.S. drone operations, widely seen as the hallmark of this light-footprint strategy, have proved particularly controversial. Pointing to the problems with using force against targets outside of traditional battlefields, critics have called for more transparency regarding targeting decisions and civilian casualties. In an effort to enhance the legitimacy of these operations, answer questions about who is targeted, and check others’ use of drones as the technology proliferates, the Obama administration developed a set of standards to guide the United States’ employment of drones. These policies included a requirement for near certainty—the highest achievable standard—that no civilian would be injured or killed in the strikes. President Barack Obama also issued an executive order requiring the director of national intelligence to provide an annual report on civilian casualties from U.S. strikes undertaken outside traditional battlefields.

Although the likelihood of another 9/11 has diminished, it is far from zero.

But a light-footprint approach alone is not always sufficient. In some places, such as Libya and Yemen, the lack of stable governance and capable partners on the ground has made it impossible to sustain military gains. And of course, no amount of drone strikes or raids can counter distantly inspired violence. Ultimately, the administration’s light-footprint strategy to combat ISIS and al Qaeda in Iraq and Syria gave way to what the political scientists Peter Feaver and Hal Brands have described in this magazine as the “counter-ISIS plus” approach. The Obama administration stepped up operations in Iraq and Syria, increasing the number of troops and advisers there and launching a more aggressive air campaign and a series of special operations raids. In Libya in late 2016, the U.S. military conducted air strikes in support of Libya’s interim government to rout ISIS from its nascent safe haven in Sirte. These operations were guided by certain criteria: the United States would work in support of local forces except to counter an imminent threat that its partner could not or would not respond to, and it would seek to lend these operations legitimacy by sending thought-out public and diplomatic messages about their nature and purpose. 

To deal lasting blows to ISIS and al Qaeda, and to keep others from seizing new safe havens, the United States will need to continue some variant of this stepped-up strategy. So far, President Donald Trump’s plan to defeat ISIS closely resembles that of his predecessor—albeit with the additional element of delegating greater authority to commanders in the field. But military operations will always be half measures if they are not paired with a strategy to make U.S. partners more viable—security assistance and diplomatic engagement aimed at getting countries to govern inclusively, bolster their security sectors, and reform their economies. That’s why the Trump administration’s proposed budget cuts to the State Department—at a time when military leaders regularly call for increases in foreign aid—are so worrisome. 

Memorial wreaths at the Pulse nightclub in Orlando, Florida, one year after the massacre, June 2017
Scott Audette / Reuters


Pressure on safe havens will merely keep a lid on a threat from terrorists who are growing more creative by the day. As technology advances, so do terrorists’ capabilities to exploit it. Consider the next generation of aviation threats. From AQAP’s 2010 plan to stow printer cartridges filled with explosives in airplane cargo holds to ISIS’ recent plot in Australia, terrorists have shown a determination to overcome the post-9/11 security obstacles to bringing down airliners. The Trump administration has wisely put an emphasis on aviation security. In March, for example, it issued a temporary ban on the use of laptops in the passenger cabin on flights originating from certain airports. The administration threatened to extend the ban to all U.S.-bound flights, prompting some international carriers to improve their security measures. The government should continue to focus on aviation security, but it should go further and partner with the private sector to generate innovative methods of detecting new explosive materials. 

Terrorists, of course, are doing their own innovation, and some of them have even experimented with drones. In 2013, for instance, Iraqi officials announced that they had thwarted a plot in which al Qaeda operatives intended to use toy planes to deliver sarin and mustard gas. Adding to the danger, more and more devices are going online as part of “the Internet of things,” creating new vulnerabilities that ISIS and others could exploit. That’s why the Trump administration should heed the call from the 2016 report of the Commission on Enhancing National Cybersecurity to work with the private sector to build security features into new technology at the design stage, rather than play catch up with terrorists’ attempts to commandeer such devices. The United States’ future safety demands that it, and not its adversaries, dominate the technological domain. 

The innovation that has benefited terrorists the most, however, is social media. Lone wolves are never truly alone; they deliberately search for and find communities online. To draw in vulnerable youth, ISIS has created a sophisticated media machine that pumps out professionally produced videos, multilingual tweets, a glossy magazine, and Instagram posts, all serving up an intoxicating narrative that followers can belong to a cause greater than themselves. Other groups, including al Qaeda, are now mimicking ISIS’ tactics. Gone are the amateur videos of al Qaeda’s leader Ayman al-Zawahiri sitting cross-legged before a drab backdrop; those rare releases are now dwarfed by al Qaeda’s Syrian branch’s steady stream of slick videos and magazines.

No amount of drone strikes or raids can counter distantly inspired violence.

The U.S. government has struggled to beat terrorists at the social media game, but Silicon Valley is taking promising steps. In June, a group of technology companies created the Global Internet Forum to Counter Terrorism, a consortium devoted to making their platforms less hospitable to extremists. Facebook, which boasts more than two billion active monthly users, is employing artificial intelligence and image-matching technology to stop known terrorist content from proliferating. Twitter, for its part, has suspended more than 375,000 accounts promoting terrorism. Deleting by hand after the fact will not suffice, however, and so social media platforms will need to train their algorithms to detect extremist content—international and domestic—and banish it immediately.

At the same time, companies will need to ramp up their support for legitimate voices that rebut terrorists’ narratives. Jigsaw, a think tank created by Google, has developed the Redirect Method, a project that targets online users who have been identified as susceptible to ISIS’ messaging and serves them alternative content that subtly debunks terrorist propaganda. The government can play a role, too—not as the messenger but as a partner to the private sector. In 2016, the State Department launched the Global Engagement Center, an office dedicated to supporting voices that rebut terrorists’ messaging. But so far, Secretary of State Rex Tillerson has refused to spend the $80 million already earmarked for the center, which currently lacks a director and is losing some of the private-sector talent recruited last year. The Trump administration should support, not sideline, its work.


What may most influence the future terrorist threat, however, is not the flourishing of physical and virtual safe havens per se but the breakdown in order that is sure to spawn more of both. Today, old and new powers are seeking to redraw the map. Across the Gulf and the Levant, and even in Afghanistan, Iran and its proxies are promoting and taking advantage of instability. Russia is doing the same in eastern Europe, and it has worked hard to protect its client in Syria and create a new one in Libya. The future threat will be defined by these areas of chaos—the safe havens presented by them, the foreign fighters drawn to them, and the violence inspired by them.

So there is a dangerous irony in Trump’s invocation of “America first,” a message that has caused U.S. allies to wonder whether they can still count on Washington to continue as a partner in—if not the guarantor of—their security. If the United States pulls up the drawbridge in the name of protection, it may deny itself counterterrorism tools that are essential to the country’s safety. By banning the travel of all citizens from certain countries, rather than tailoring screening to specific threats, the United States risks alienating the very partners it needs to fight today’s terrorists and fueling the “clash of civilizations” narrative that ISIS uses to recruit future ones.

As the campaign against ISIS has laid bare, partnerships with local allies are the key to successfully taking back territory from terrorists. The same is true when it comes to interdicting foreign fighters. In the past, the United States has taken the lead on working with foreign governments to share watch lists, improve border security, and impose new criminal penalties on foreign fighters. Experts have warned that as ISIS’ territory in Iraq and Syria shrinks, some 40,000 fighters who came from more than 120 countries to fight for ISIS could start to return home. But given that some of these fighters have spent years perfecting their violent craft on the battlefield, the greater concern may now be “not so much one of quantity as one of quality,” as Nicholas Rasmussen, the director of the National Counterterrorism Center, put it earlier this year. 

Europe will continue to face an immediate threat from skilled returnees of the type that participated in the 2015 Paris attacks and the 2016 Brussels bombings. Unfortunately, however, the continent has yet to experience the kind of sea change that occurred in the United States, which radically rethought its practices for sharing information among law enforcement and intelligence agencies. In many European capitals, the wall impeding such sharing is far too high. And since the Atlantic Ocean is not a perfect buffer, what happens in Europe matters for the security of the United States. So rather than confusing U.S. allies with travel bans and mixed messages about the value of NATO, the United States should expand its counterterrorism cooperation with its European partners. For example, it should press its partners to more rapidly share airline passenger data and intelligence gleaned from investigations. And it should resume the dialogue begun by James Clapper, the former director of national intelligence, on promoting intelligence sharing with and among European countries.

It would be a mistake, however, to look only outward, ignoring the growing terrorist threat at home. The hit-and-run murder of a peaceful protester in Charlottesville, Virginia, by an avowed white supremacist is only the most recent reminder that the United States has a terrorism problem unrelated to violent jihadism. The challenge that bedeviled both the Bush and the Obama administrations—building trust between communities and their government to address extremism in all its forms—seems harder than ever. And lately, this important work has suffered from neglect. The Trump administration has proposed a budget that zeroes out funding for a Department of Homeland Security program aimed at countering violent extremism and has already withdrawn a grant for a group dedicated to combating domestic hate groups such as the Ku Klux Klan. 

Sixteen years after 9/11, many Americans are weary of the war on terrorism. Having built up its defenses, the United States should no longer go abroad in search of monsters to destroy, some contend. Instead, they say, it should stick to keeping the bad guys out and adjust to a new normal in which some attacks are inevitable. But it would be a grave mistake to confuse a mitigated threat with a weak one. Rather than resignation, Americans will have to demonstrate resilience—just as New York, Fort Hood, Boston, Charleston, San Bernardino, Orlando, Portland, and Charlottesville have done in the face of hate and violence. To date, the United States’ strategy has succeeded in preventing another 9/11-type attack, largely because it built a net designed to do just that. But for the next phase in the war on terrorism, the country will need a new net. It cannot afford to operate without one.

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  • LISA MONACO is Distinguished Senior Fellow at New York University School of Law and a Senior Fellow at Harvard Kennedy School’s Belfer Center for Science and International Affairs. From 2013 to 2017, she served as Homeland Security and Counterterrorism Adviser to U.S. President Barack Obama.
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