The only casualty was the bomb-maker himself, an Islamic State sympathizer who was shot and killed as he lunged at police, armed only with his fists.
As an act of terrorism, the June 20 attempt was a merciful failure. Yet it also bore hallmarks that are becoming increasingly familiar to Western officials who monitor attacks by the terrorist group in countries around the globe: simple plots, crude weapons and inexperienced perpetrators who act alone, without apparent direction or training.
A State Department report released Wednesday underscores the persistence of the terrorist threat posed by the Islamic State, which despite military setbacks posted a record number of attacks and fatalities in 2016, surpassing all other militant groups worldwide. But at the same time the sophistication of the group's operations is slipping, suggesting that counterterrorism measures arrayed against the militants is taking a toll, U.S. and European counterterrorism officials say.
With its Iraqi and Syrian sanctuaries nearing collapse, the Islamic State is facing new difficulties in dispatching operatives to targets, and its communications and financial networks are under unprecedented strain, analysts said in interviews. As a result, they say, terrorist leaders are becoming ever more reliant on volunteers who lack training and act with little or no coordination or guidance.
"We are talking really about low-key losers," said a senior Belgian law enforcement official, describing what he called a shift in the predominant terrorist threat his country faces. The official, who insisted on anonymity to discuss intelligence assessments, said that Belgium's biggest problem is no longer the foreign fighters or returnees, but the "homegrown, who never left for Iraq and Syria."
The implications are mixed. Some "lone wolf" attacks can be spectacularly successful, as in the case of the May 22 suicide bombing in Manchester, England, that killed 23 concertgoers and wounded 250. Moreover, plots by solitary actors are more difficult to detect and disrupt, and the number of potential volunteers can be vastly larger, compared to trained terrorist cadres in sleeper cells.
But the trend also is viewed as further evidence of disarray within the Islamic State, a terrorist organization that once seemed unstoppable. Nearly unnoticed among the recent military victories are countless smaller successes, U.S. and European officials say, ranging from the targeting killings of the Islamic State operational commanders, to the shuttering of financial networks, to the disruption of dozens of plots by intelligence and law enforcement officials worldwide.
The group's increasingly urgent appeals for lone-wolf attacks is proof that such efforts are working, said Justin Siberell, the State Department's acting coordinator for counterterrorism.
"ISIS directed its followers to attack in their home countries rather than attempt to travel to the conflict zone," Siberell said. He described the pleas as an "acknowledgment of the more difficult environment" within the group's self-proclaimed caliphate.
Most analysts predict that terrorist attacks will continue and perhaps increase in the near term. But the setbacks are making it harder for the militants to plan and execute the kind of sophisticated operation that could inflict widespread damage and large numbers of casualties, said Daniel Benjamin, who helped direct the State Department's counterterrorism efforts during the Obama administration.
"The improvements never seem like enough, especially in an era when you can have a motivated individual carrying out a truck attack or using semiautomatic weapons to spray gunfire," said Benjamin, who heads the John Sloan Dickey Center for International Understanding at Dartmouth College. "Some of these things you won't be able to stop. But overall, the organized conspiracy has become much more difficult."
The State Department's report, an annual assessment of terrorism trends in countries around the world, is a global portrait of 2016, a year in which the Islamic State retained control of much of northern Iraq and eastern Syria and helped guide numerous large-scale terrorist attacks aboard, including airport bombings in Brussels and Istanbul.
Even as terrorist attacks overall fell by more than 9 percent that year, the Islamic State "remained the most potent terrorist threat to global security," the report said. The group's operatives carried out more than 1,100 attacks worldwide that claimed more than 9,000 lives, the bulk of them in Iraq.
Those exits are effectively sealed, U.S. officials say.
"Foreign fighters are not coming into Syria anymore," Brett McGurk, the U.S. envoy to the coalition fighting the Islamic State, said in a briefing last week. "And those who are already in Iraq and Syria - we've been working very hard to make sure that they can never get out."
By late 2016, hundreds of militants had returned to Europe, some of them blending in with the streams of Syrian and Iraqi refugees heading north. But with each liberated Iraqi town and city, the U.S.-led coalition has seized troves of computer data, including personal details and photos of thousands of Islamic State recruits. In recent months the data has been shared with U.S. allies from northern Europe to Southeast Asia, leading to dozens of arrests, counterterrorism officials say.
Other initiatives - some of them secret - have shut down communication networks used by the Islamic State to send instructions abroad. Even the number of social-media channels used by the militants has plummeted, from 40 active sites in 2015 to just 19 at the beginning of 2017.
Meanwhile, the Islamic State's cash supply has dwindled to the point that it constantly struggles to meet its payroll, with little or nothing left over to send to regional affiliates or to finance terrorist operations abroad, said a senior U.S. counterterrorism official who tracks the group's finances.
"We're seeing pay cuts for fighters and pay cuts for employees, missing payments, deferred payments, more criminal activity to supplement incomes," said the official, who requested anonymity to discuss intelligence assessments. "We see them trying to hide money, perhaps for personal gain or to make sure they have something after the caliphate falls. But it's very hard."
As the pressures increase, so do the pleas from Islamic State leaders for outside help. Last week, as the last of Mosul's neighborhoods were being retaken by Iraqi forces, the terrorist group posted an appeal in its online magazine, Rumiyah, urging "lone-wolf" supporters to strike blows against the West using any means available. The message even called for the kidnapping of children to raise money for the terrorist group.
"Invest your time in everything that enrages the kuffar [infidel], affects and weakens them, destroys their morale and inflicts the great damage upon them," the article said. "Make this your habit for yourself and your family." The same edition included an article lionizing perpetrators of failed attacks, including Ousama Zariouh, the 36-year-old man behind the unsuccessful bombing of the Brussels train station on June 20.
Previous postings have suggested elaborate weapons and plots, from chemical toxins to coordinated train derailments. But more recent messages have emphasized simpler methods. One missive, posted in late June, included elaborately detailed instructions on how to obtain the right kind of truck for running over pedestrians. The tone of the message hinted at impatience and exasperation.
"Cannot one of you stab a filthy Crusader," it asked, "or run him over with your car, or throw him from a high place, or put poison in his food?"
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