This latest attack in Brussels would not have been possible without this network of native-born, disaffected Muslims. And for that, Europe has no one to blame but itself.

Last week, I wrote about the myriad instabilities in the Middle East and North Africa, from the civil war in Yemen to the bombings in Turkey and the ongoing disaster in Syria. What I didn’t touch on, however, is how these instabilities are reverberating on the European continent. Sadly, this week another tremor was felt. Today, during the morning commute, terrorists bombed a train station and the airport in Brussels. So far, more than 30 are reported dead and more than 150 injured.

These attacks come five months after the Paris attacks that shocked the world and took the lives of 130 men and women. These terrorists had pledged their allegiance to ISIS and were carrying out what they believed to be holy jihad. Although most of the perpetrators were killed during the attacks or in the days after in a suburb of Paris, one man eluded the police. That man, Salah Abdeslam, was captured on Friday after a months-long manhunt.

The city has been on high alert since his arrest. They knew Abdeslam had a large network in Brussels, and that he had been planning more attacks. They feared his network of operatives would lash out. They also discovered detonators in a safe house last week before his arrest. Presumably, today’s bombings in Brussel were a reaction to Abdeslam’s apprehension, either out of concern that he would talk or that the police would soon be on to them, too.

What is shocking the Brussels police, however, is the scale of Abdeslam’s network and its capacity to help him avoid capture for so long in a city that authorities were scouring for him. On the night of the Paris attacks, Abdeslam crossed the border into Belgium with the help of a friend. Although his name was flagged as a person of interest, the border guards’ system had not yet been updated with the information that he was one of the suspects. From there, it’s presumed that he returned home to Brussels, where he continued planning more attacks.

How is it that in a prosperous European country there can be enough support within the Muslim community for a man who had pledged his allegiance to ISIS?

In the months before the Paris attacks, he and the Syrian fighters with whom he linked up were helped by Abdeslam’s family, childhood friends, and other petty criminals to remain concealed. In the months after the attacks, he was helped by what it seems is a massive network of “friendlies” who were willing to shelter, hide, and perhaps even work with him on the next terrorist plot. When Abdeslam was finally apprehended, he was living a few hundred yards from his family’s home—right under the nose of the police.

Here we come to the crux of the problem. How is it that in a prosperous European country there can be enough support within the Muslim community for a man who had pledged his allegiance to ISIS, has already successfully completed one terrorist attack and is planning others, to be protected and aided?

The answer is that this is a problem of Europe’s own creating—and it’s not going away. Beginning in the post-World War II era, Europe was in need of workers to pad its depleted work force. A natural place to look was North Africa, in former colonies of Spain and France. While it was assumed that migration would be short-term, the reality is that the men who came to work stayed, and later brought over their families. Europe made no plan for how to house and assimilate these families (see Christopher Caldwell’s excellent book, “Reflections on the Revolution in Europe,” for an in-depth discussion of this topic).

More to the point, Europe was uncomfortable asking its Muslim communities to assimilate. European leaders felt that would be too reminiscent of the colonial era. Their guilt and newfound “enlightenment” guided them to leave these people to their communities, culture, and religion. At the same time, however, they also ostracized them. What resulted was tight-knit majority-Muslim enclaves often on the outskirts of major European cities (like Saint Denis on the outer edge of Paris, where one of the Paris attackers was found).

They are loyal, at best, to the local Muslim community with whom they share a sense of solidarity, or in its worst manifestations, to ISIS and its global sense of destiny.

These communities are volatile places that are not dissimilar, in some ways, to certain American inner cities. They remain close-knit via shared language, Arabic, shared religion, Islam, and a continued influx of immigration from their countries of origin. This is no longer just family reunification. It is common, for example, for second- and third-generation North African immigrants to look to their ancestral home for a spouse. This is most common among men. They want a woman uncorrupted by European values. These marriage practices keep a continuous supply of first-generation mothers having second-generation children.

These problems have now come home to roost. Europe has on its hands millions of Muslims, many of whom, although certainly not all, identify first as Muslims and second as Europeans. They are loyal, at best, to the local Muslim community with whom they share a sense of solidarity, or in its worst manifestations, to ISIS and its global sense of destiny. This manifests itself in its most extreme in attacking the great evil that is the West—even if it has been their home for their entire life. But, as has played out in the last few months, it is also manifesting itself in a large community of people willing to aid and abet terrorist networks in Europe.

What makes this situation so unique, and so dangerous, is the cooperation of foreign and domestic operatives. Syrian fighters, who, according to the Belgian Justice Minister Koen Geens, are coming over “constantly,” are wholly unfamiliar with Europe. But because they are plugged into a network of people who are not themselves terrorists but have little allegiance to Europe and have all the necessary local knowledge, the would-be terrorists can easily move undetected and successfully execute their attacks.

This latest attack in Brussels would not have been possible without this network of native-born, disaffected Muslims. For that, Europe has no one to blame but itself.