On January 27, President Donald Trump signed a 2,855-word executive order titled PROTECTING THE NATION FROM FOREIGN TERRORIST ENTRY INTO THE UNITED STATES. The order placed a temporary ban on people from seven predominantly Muslim countries entering the United States (and an indefinite ban on migrants from Syria—most of whom are refugees). His justification was to protect Americans from the threat of terrorism, but the order seems unlikely to accomplish this goal.

It was met with widespread fury, not just in the U.S. but across the world. And opposition was not confined to the usual suspects. Two Republican senators and leading national security figures, John McCain of Arizona and Lindsay Graham of South Carolina, issued a joint statement in which they said: "Our most important allies in the fight against [the Islamic State] are the vast majority of Muslims who reject its apocalyptic ideology of hatred. This executive order sends a signal, intended or not, that America does not want Muslims coming into our country. That is why we fear this executive order may do more to help terrorist recruitment than improve our security."

Could they be right? Is Donald Trump effectively acting as an ISIS recruiting sergeant? The research we and other social psychologists have conducted in recent years suggests that the answer is probably yes. 

Fueling extremes

For starters, consider the fact that, when Trump announced his intention to ban Muslims from the U.S. on the campaign trail, ISIS promptly re-aired the announcement as part of its propaganda offensive. At the time, General James Mattis, now Secretary of Defense, said the proposed ban was “causing us great damage.” ISIS leaders also used news of Trump’s election victory as a rallying cry, celebrating it as heralding “the imminent demise of America.”  And, although it is too early to gauge the full reaction to this latest escalation, jihadist groups have already hailed the “blessed ban” as proof the U.S. is at war with Islam—with one group going so far as to describe President Trump as “the best caller to Islam,” according to the Washington Post.

All the early evidence indicates that the seven-nation ban doesn't fight fire with fire—as President Trump contends—but rather adds fuel to that fire. The reciprocal dynamic here could not be clearer: Trump feeds off ISIS and ISIS feeds off Trump. This is part of what Douglas Pratt from the University of Waikato in New Zealand refers to as co-radicalization . Extreme actions and statements are used to provoke others to treat your own group as dangerous—and that helps to consolidate followers around those very leaders who preach greater emnity.  

Here lies the real power of terrorism. It is not so much about spreading fear as it is about seeding retaliation and further conflict. ISIS (or ISIL) exploits this dynamic with ruthless effect. Their core narrative, and the basis of their propaganda appeal, is very simple. According to Ben Rhodes, a deputy national security advisor in the Obama administration, the narrative goes like this: "ISIL is the caliphate. They are representatives of all Islam. Islam is a war with the West and the United States. And therefore, Muslims have a responsibility to come join ISIL and to fight in that war." The aim of their actions is to goad Western nations in acting in ways that give credence to this narrative.

ISIS Boot camp, 2014. Credit: Karl-Ludwig Poggemann Flickr (CC BY-SA 2.0)   

Accordingly, the ISIS magazine Dabiq explained the January 2015 attacks on the headquarters of the French magazine Charlie Hebdo in the following way: "The time had come for another event—magnified by the presence of the Caliphate on the global stage—to further bring division to the world." Later in 2015, Dabiq carried an editorial that bemoaned the fact that many Muslims did not see the West as their enemy and that many refugees fleeing Syria and Afghanistan actually viewed Western countries as lands of opportunity. They called for an end of the “gray zone” of constructive coexistence and a world starkly divided between Muslims and non-Muslims. ISIS deliberately carried out further attacks—notably in Paris in November 2015—to try to bring this rift about.

In short, terrorism is all about polarization. It is about reconfiguring intergroup relations so that extreme leadership appears to offer the most sensible way of engaging with an extreme world. Or, as we put it in an article for the May 2016 issue of Scientific American Mind, terrorism fuels extremes. From this vantage, terrorist acts are the very opposite of mindless destruction. They are part of a conscious—and effective—strategy for drawing followers into the ambit of confrontational leaders. For this reason, as David Rothkopf wrote in Foreign Policy following the Paris massacres, "Overreaction is precisely the wrong response. And it is exactly what terrorists want ... it does the work of terrorists for the terrorists."

Trump's Executive Order is even more harmful than most overreactions. It is not even a response to some outrage. And it gives especially strong ammunition to those in ISIS and other groups who argue that Americans see Muslims as their enemy and hence act as the enemy of Muslims. Moqtada al-Sadr, a leader of the anti-American insurgency in Iraq, responded immediately to Trump's ban by arguing that Americans be thrown out of his country. Renad Mansour, a Middle East expert at Chatham House points out in TIME that Sadr and others can now say to those Muslim moderates who challenged their “apocalyptic ideology of hatred” (to reprise the words of McCain and Graham): "I told you so."

Preventing or provoking extremism?

So why, if it helps his enemies, does Trump act in this way? One simple answer is that he doesn't realize what he is doing and genuinely believes his actions will be effective. If so, he wouldn't be alone. Indeed many contemporary counter-terrorism efforts ignore the ways in which policy and practice serve to bolster the influence of extremists. Take, for instance, the U.K.'s flagship PREVENT program aimed at countering radicalization. The problem with this kind of approach is that focuses exclusively on “them,” members of the Muslim minority, and it fails to address what “we,” the majority, do. As a consequence, it cannot account for what former CIA Operations Officer and Government counter-terrorism advisor Marc Sageman calls “the problem of specificity.” That is, many groups provide the bonds of fellowship around a shared cause: sporting groups, cultural groups, environmental groups. Even among religious groups—and specifically Muslim groups—the great majority provide community and meaning without promoting violence. So why are some people drawn to the few Muslim groups that do preach violent confrontation?

The answer, as we have explained above, comes from looking at the experiences that render the terrorist narrative credible. To explore these dynamics in action, in 2013, one of us (Reicher), working with Leda Blackwood at Bath University and Nicholas Hopkins at Dundee University, conducted a series of individual and group interviews at Scottish airports. As national borders, airports provide clear signals about belonging and identity.

We found that most Scots—Muslim and non-Muslim alike—had a clear sense of “coming home” after their travels abroad. Yet many Muslim Scots had the experience of being treated with suspicion at airport security. Why was I pulled aside? Why was I asked all those questions? Why was my bag searched? We termed this experience of having others misperceive or deny a valued identity “misrecognition.” It systematically provoked anger and cynicism toward authorities.

To be clear, misrecognition did not instantly turn otherwise moderate people into extremists, but it did begin to shift the balance of power away from leaders who say “work with the authorities, they are your friends” towards those who might insist, “the authorities are your enemy.” It is reasonable to assume that the many individuals detained at U.S. border crossings in the wake of Trump’s executive order have started to experience that shift.

Cui bono?

It might be that Trump, like many others, fails to recognize the impact of his own actions in spurring precisely what he aims to curtail. But there is another explanation, based on an old legal principle: if you want to solve a crime, simply ask cui bono—who benefits?

The fact is that President Trump stands to make enormous political gains among his base with the ordered ban, however counterproductive. A leader must be seen to be in control and capable of keeping his or her people safe; it is, as the classic political theorist Thomas Hobbes argued, the primary justification for any form of government. And this stance may be particularly important for someone like Donald Trump, who came to power by promising he is a man of action.

Also, extremist leaders gain credibility precisely because they accrue adversaries. In 2015, one of us (Alex Haslam) published a series of experiments in The Leadership Quarterly with Ilka Gleibs at the London School of Economics looking at how people choose leaders. One of our core findings was that people are more likely to support an extremist if their group is confronted by, and in competition with, another group that is behaving belligerently. As we argue in the latest issue of Scientific American Mind (March/April 2017), Trump appealed to voters by presenting a polarized view of the world in which they were under threat from both external enemies (Muslims, Mexicans, the Chinese) and internal ones (the media, the liberals and the political establishment).

In short, Donald Trump needs enemies to validate his worldview as much as ISIS needs an American enemy to validate theirs. As long as Trump's provocative actions make him an effective recruiting sergeant to his own cause, we cannot expect him to stop doing things that make him an equally effective recruiting sergeant for ISIS.