Police control the access to Brussels central train station following Tuesday's bomb attacks in Brussels, Belgium, March 23, 2016.
Vincent Kessler / Reuters

After the March 22 terrorist attacks in Brussels, for which the Islamic State (ISIS) has claimed credit, it is time to start thinking more seriously about how to thwart the group. 

In this, it is important to keep in mind that ISIS is not al Qaeda. For one, the ISIS-sponsored network in Europe includes at least 90 well-trained, well-supported, and well-supplied operatives. Their tactics were honed on hot battlefields and in the bombed-out basements of war-torn Syria, not at terrorist boot camps or in the caves of the Hindu Kush, as was the case for al Qaeda. And whereas al Qaeda members mainly carried Middle Eastern passports, many ISIS members travel on European documents; the majority of those who attacked Paris in November are thought to have been citizens of European Union countries. The same is likely true of the Brussels bombers. That gives ISIS an advantage as it strikes at harder and harder targets. 

Second, beyond ISIS’ core Western network are scores of unaffiliated or loosely affiliated jihadists. In fact, many of the so-called ISIS attacks have no direct logistical links to the group and are mainly inspired by propaganda and online resources. All of the ISIS-related attacks in Australia, Canada, and the United States thus far fit into this mold, including the December 2015 San Bernardino assault that killed 14 people and injured 21 others. Al Qaeda kept tighter control of those it allowed to claim its brand.

Broken windows of the terminal at Brussels national airport are seen during a ceremony following bomb attacks in Brussels metro and Belgium's National airport of Zaventem, Belgium, March 23, 2016.
Broken windows of the terminal at Brussels national airport are seen during a ceremony following bomb attacks in Brussels metro and Belgium's National airport of Zaventem, Belgium, March 23, 2016.
Yorick Jansens / Reuters
In short, the ISIS threat is more akin to the state-sponsored terrorism emanating from Iran, Iraq, Libya, the Soviet Union, and Syria during the 1970s and 1980s. Groups with the known backing of states (such as Hezbollah and many of the Palestinian groups) had access to greater resources, more logistical support, better intelligence, better weapons, and wider networks than those that operated on their own (such as the Weathermen or the French group Action Directe). State-backed groups were always more dangerous. The parallels today should come as no surprise, thanks to ISIS’ provenance in Syria and the participation of Saddam Hussein–era Iraqi Baathist military officers in the group’s operations. But this time, the strategy is on steroids, driven by a sharp social media campaign for recruitment and logistical connections.

Given that ISIS’ tactics are more like state-sponsored terrorism than al Qaeda–style operations, how should the West respond?

To be sure, counterterrorism can contribute to the response. Network analyses, counterfinancing, deradicalization, and special operations strikes are all useful. Old-fashioned and unglamorous police work—collecting forensic evidence and interrogating captured prisoners such as Salah Abdeslam (the sole survivor of the Paris attacks)—will be even more crucial, as will police and intelligence coordination within the EU. In particular, Belgians will need to strengthen their domestic security: everyone knew that Brussels, the capital of Europe, was a ripe target for ISIS-trained Belgian and French citizens. Belgium’s failure to prevent the attack when it did come reveals systemic problems.

The West must shrink ISIS territory, stabilize the surrounding area, and find an international solution for the vast number of Syrian refugees who are still in the region.
But ISIS is not just a terrorist group, so counterterrorism won’t be enough. The group has more than 30,000 fighters and is able to field a real army, hold territory in Iraq and Syria, and confront military forces. Al Qaeda never attracted 1,000 foreign fighters a month, including women and children, or forced hundreds of thousands of civilians to flee its occupied territory. A core element of any anti-ISIS strategy, in other words, should be diminishing its state-like safe haven, from which it can prepare larger attacks. And that will require some level of conventional military force.

Here, the United States can help. After 9/11, it built an enormous edifice to target al Qaeda, spending more than $1.6 trillion on the global war on terrorism since 2001, and erecting some 263 new or reorganized counterterrorism agencies. But the resulting structure is suited more to classic terrorism movements than to countering a pseudo-state capable of projecting force abroad. Counterterrorist tactics will not be sufficient unless they are nestled into a broader integrated strategy that considers the full range of activities, meaning everything from military operations to humanitarian assistance. At the moment, U.S. counterterrorism agencies and paramilitary forces are highly reactive and virtually autonomous. Using military force in Syria and Iraq is essential, but it will have little effect in the absence of a viable political objective. 

A man attends a memorial gathering near the old stock exchange in Brussels following Tuesday's bomb attacks in Brussels, Belgium, March 23, 2016.
A man attends a memorial gathering near the old stock exchange in Brussels following Tuesday's bomb attacks in Brussels, Belgium, March 23, 2016.
Christian Hartmann / Reuters
There are wider risks in relying too much on the military as an answer to this threat. For example, Syria’s descent into civil war in 2013 followed by ISIS’ sweeping territorial conquest in 2014 set off a massive panic. Some 4.5 million Syrians have fled the country, and another 6.5 million are internally displaced. Year after year, the international community pledged aid at high-profile conferences, but these pledges often went unfulfilled. Meanwhile the United States focused primarily on air strikes and military support for the Iraqi security forces, mostly ignoring the far more destabilizing humanitarian disaster. That left open the possibility for ISIS to exploit the refugee situation in two ways. 

First, ISIS has been able to use the wave of refugees to overwhelm efforts to track their operatives’ movements. Bickering between European states about border controls and intelligence sharing has and will only continue to help ISIS. Second, through terrorist attacks, the group has tried to manipulate Western publics to further polarize populations against the migrants, which will alienate domestic minority groups. In the future, ISIS will continue to rely on well-trained returning jihadists from Syria to orchestrate military-style attacks and local volunteers who are willing to either help or engage in their own less sophisticated attacks. 

So, countering this state-sponsored threat, including its terrorist attacks, will involve a number of things. Counterterrorism, sure, but also not succumbing to the tendency to blame all those who are fleeing ISIS territory for the horrible terrorist attacks that have unfolded under the purview of ISIS-supporting Europeans. Meanwhile, the West must shrink ISIS territory, stabilize the surrounding area, and find an international solution for the vast number of Syrian refugees who are still in the region. This will be no short order, of course, but the consequences of not trying are too severe.