The counterterrorism playbook used to fight groups a decade ago has proven ineffective against modern-day sympathizers of radical causes, experts say
The U.S. government has launched thousands of airstrikes, bombed oil facilities, redeployed its military, moved satellites, intercepted phone calls, blocked money transfers and made dozens of arrests in a bid to thwart Islamic State.
But time after time, the terror group, its affiliates and sympathizers have found ways to break through a global ring fence, launching spectacular attacks that have killed hundreds of people in Europe and the U.S.
The motives and perpetrators behind Thursday’s truck massacre in Nice, France, remained uncertain in the hours immediately following the attack. But the action appeared to share the hallmarks of recent attacks carried out, or inspired by, Islamic State: It was a murderous assault on a “soft,” or unprotected, target undertaken by an individual or handful of people.
Islamic State has exploited weak or nonexistent governments in Syria, Iraq, and Libya to fortify, recruit and plan attacks. Its leaders have leveraged social media to proselytize and lure new members. And they have, again and again, hammered soft targets full of crowded people. An airport. A holiday party. A concert hall. A nightclub.
In many cases, the attacks are being carried out by an individual or small number of people, sometimes without actual ties to the group that inspired them. That presents a daunting problem for intelligence operatives and law enforcement.
“The problem is that the numbers of people who have been radicalized, mostly because of social media, are larger than anything we’ve seen before, and we are just behind the curve,” said Bruce Hoffman, director of the Center for Security Studies at Georgetown University. “We are dealing with a problem of an order of magnitude much larger than in the past.”
A truck driver who plowed through crowds and murdered at least 77 people on Bastille Day in Nice, France, joined the ranks of other individuals or small groups of terrorists who have murdered dozens or even hundreds of innocent revelers, travelers and others in the past 18 months.
France’s antiterrorism prosecutor has opened a probe. No one yet has claimed responsibility for Thursday’s attack.
The attack also comes as voters across the U.S. are beginning to focus more squarely on the presidential election, with national party conventions just days away. Both leading candidates, Republican Donald Trump and Democrat Hillary Clinton, are being pressed to explain how they would rework U.S. counterterrorism policy to better thwart the resilience of Islamic State.
Their counterterrorism strategies—and teams—will likely face sharper scrutiny now. Mr. Trump has proposed banning the entry of Muslims into the U.S., ramping up interrogation techniques against accused terrorists to disrupt plots and bombing the “hell out of” the terror group in Iraq and Syria. He has said he wants to keep much of his plan a secret, though, so as not to tip off Islamic State leaders as to how he will defeat them.
Mrs. Clinton has pushed for Sunni Muslims and Kurdish forces to play a bigger role in combating Islamic State in Iraq and Syria, and she also wants to expand U.S. airstrikes. She has pushed for disrupting Islamic State’s use of the internet and social media, though she hasn’t provided specifics on how she would do this.
U.S. officials have hoped that their two-year campaign to combat Islamic State would degrade its ability to carry out terror attacks, but they have found only mixed results.
U.S. officials and U.S. allies have been able to dislodge the group from some of the territory it controls in Syria and Iraq, but the group has been able to either direct or inspire attacks in France, Turkey, Belgium, the U.S. and elsewhere. A murderous sweep during the month of Ramadan killed hundreds in Baghdad; Dhaka, Bangladesh; Istanbul; and Orlando, Fla.
The attacks have proven very difficult to stop. The counterterrorism playbook the U.S. and other countries used to thwart the large-scale attacks planned by al Qaeda more than a decade ago has been less successful against Islamic State.
At a congressional hearing earlier Thursday, Nick Rasmussen, the head of the National Counterterrorism Center, warned of the danger of low-tech terrorist attacks.
ENLARGE “While we’ve seen a decrease in the frequency of large-scale, complex efforts that sometimes span several years, we’re seeing a proliferation of more rapidly evolving threats that emerge simply by an individual encouraged to take action, who then quickly gathers the few resources needed and moves,” Mr. Rasmussen said. “The time between when an individual decides to attack and when the attack occurs is extremely compressed and allows little time for traditional law-enforcement and intelligence tools to disrupt or mitigate potential plots.”
Some of the most gruesome attacks have been carried out by a single perpetrator, a married couple or a small group.
Like these attacks, Thursday’s truck massacre in Nice, France, appears to have involved a small number of people hitting innocent civilians in a soft target.
“You have to have a driver’s license and that’s it,” said William McCants, director of the Project on U.S. Relations with the Islamic World at the Brookings Institution. “There’s nothing more to it.”
Write to Damian Paletta at damian.paletta@wsj.com
—Andrew Tangel contributed to this article