By Peter Vanham

Last month, terrorists aided by young men from Molenbeek, Belgium, went to a soccer match in Paris with a terrifying goal in mind: to detonate a suicide vest and kill hundreds of spectators. Their effort ended at the gates. But at the nearby Bataclan music hall, terrorists did succeed, killing nearly 100 people and injuring hundreds more.

Among the questions the attacks raised are this one: Why were young men from Molenbeek, a municipality of Brussels, involved, and how did that city turn into the supposed "jihadi capital of Europe"?

While the international press only learned about Molenbeek recently, the Belgian press was reporting on "no go" zones in Molenbeek some five years ago. A PR agency headquartered there decided to move out in 2011, as did a local college, after a series of robberies and other threatening attacks.

I visited then to see how bad the situation was. I lived just a few hundred yards away, and joined a pickup game on a public soccer field. It was a nice experience, but I noticed there was indeed a strange dynamic. All the women were veiled and seemed to come outside only to let small children play in the nearby playground. Some young men played football, but more were just hanging out around the field. All were of North African origins, and most, I learned, were Muslim.

A Muslim neighborhood in itself is not a problem. The issue is the mix of misguided economic and integration policies over the last 50 years that have made Molenbeek what it is today. These policies came together in a perfect storm last month.

The first policy regards "guest workers." Their story starts in 1964, when Belgium and other countries set up a bilateral agreement with Morocco to bring workers to Western Europe. The Moroccans could earn a living mostly as blue-collar workers in mines, oil refineries, and factories, as our country was short of such workers. The program was intended as a short-term solution to a worker shortage, and at first, all was well.

But soon, integration problems began. Belgium had never intended for these workers to stay and had invested only limited means and thought into integrating them. Learning Dutch or French, the two official languages in Brussels, was not mandatory, and as a result, many immigrants never got around to culturally integrating. In fact, it was only last year - 50 years after the program began - that new migrants had to follow a mandatory integration course.

The second policy mistake was "family reunion." Once it was clear that temporary migrant workers intended to stay, the Belgian government, after a few years, opted for a policy of allowing workers' family members to immigrate. But that, too, had unintended consequences. The women joining their husbands were never supposed to fill a job-market void, and, not knowing the language, they often were isolated at home instead. Again, 50 years later, that problem persists. The unemployment rate among third-generation migrants is still very high, especially among women, where it surpasses 20 percent in Molenbeek.

A third policy mistake involves religion. As most arriving Moroccans were Muslim, over time they set up mosques to practice their faith. But in Brussels, as in many other places, the imams teaching the faith are often sent from foreign countries, including Saudi Arabia, mostly lecture in Arabic, and at least in some cases teach Wahhabism, a strictly conservative and reactionary version of Islam.

It is not hard to see why there are problems when you have poorly integrated and often unemployed people who are taught a sometimes radical version of Islam. But matters in Molenbeek are possibly worse than elsewhere because of the particular political situation.

The fourth mistake is the governing structure of Brussels. Because of a complex history of federal reforms, Molenbeek, merely a mile away from Brussels' central Grand Place, is a largely self-governed municipality. That serves its political class well, as it gets to appoint its own mayor and policymakers. But it serves the population as a whole much less.

The Brussels metropolitan area is governed by 19 different mayors, and each municipality has its own priorities. Each mayor pursues his or her own policies based on the wealth of the citizens. In the case of Molenbeek, tax income is extremely low as it is Brussels' second-poorest municipality, with an average annual income of less than $12,000. Integration projects and public education are thus chronically underfunded, and many social needs cannot be adequately addressed.

In such an environment, problems can quickly spiral out of control. And when they do, there is no stopping them because of the final policy mistake: the police structure. Just as there are 19 mayors in Brussels, there are also six different police zones, each with its own force, its own chief, and its own funding and priorities. Commit a petty crime in one municipality, escape to another, and, if you're lucky, you stay out of police hands.

Shortsighted immigration and guest-worker policies, and troubling family reunion rules and faith leaders, all combined with a fragmented political and police structure: That is the cocktail that exploded last month in Brussels.

If Molenbeek youths are not to be involved in another terrorist attack, Belgian political leaders at the federal and municipal level will need to step up their game and change the structures at the heart of this disaster.

Peter Vanham is a former Inquirer intern living in Brussels. He is a global leadership fellow at the World Economic Forum.