“What we feared has happened. We were hit by blind attacks.”

That’s how Belgian Prime Minster Charles Michel described Tuesday’s attacks in Brussels. They point to the paradox at play in the tiny, divided Low Country nation: Ever since the Paris attacks in November 2015, Belgian counterterrorism officials have been on high alert, and yet they correctly worried that deadly violence was inevitable. While the details of the attacks remain to be discovered and reconstructed, there are still some hints of why it was so hard to prevent an attack. Belgium has long been a center for Islamist terrorism, but certain aspects of the state’s structure and relationship with Europe also made it difficult for the government to fight back.

Thomas Joscelyn, senior fellow at the Foundation for Defense of Democracies and senior editor of The Long War Journal, echoed Michel’s point on Fox News Tuesday morning.

“If you talk to any Belgian counterterrorism or intelligence officials, no one—no one—is surprised by this,” he said. “You can go all the way back to 2014 to Belgian authorities saying this was coming. They’ve launched a series of counterterrorism raids because they know that known terrorists are operating on their soil. This is the least surprising outcome that you could see.”

The Paris attacks were carried out by a team that included Belgian nationals and residents. Belgium has a sizable Muslim population—roughly on par with that of other Northern European countries—but by some tallies has sent more fighters to join ISIS per capita than any other country in Europe. In Brussels’s Molenbeek neighborhood, the epicenter of Belgian jihadism, there’s high unemployment, an isolated Muslim population, poor education, and a lack of government services.

These problems were not unknown before the Paris attacks. Belgium has grappled with Islamist terrorism since as far back as the 1980s, and various observers had voiced concerns about jihadism in Molenbeek and lack of policing prior to last November. In January 2015, for example, following attacks on Paris offices of the satirical magazine Charlie Hebdo, Belgian authorities launched a series of terrorism-related raids, sweeping up suspects. “The Belgian police may claim today to have ‘averted a Belgian Charlie Hebdo,’ but it’s clear that the country’s radicalization problem is much larger, and will take more than police raids to address,” Slate’s Joshua Keating warned at the time.

After the Paris attacks of November 13, Belgium further stepped up its counterterrorism efforts, with police launching raids in Molenbeek in the days immediately afterward. “You have a very high concentration in Molenbeek and that could well be the essence of the story,” said Interior Minister Jan Jambon at the time. “Moreover, local authorities have been rather lax in this respect for many years.”

From November 21 to 25, the enforcement expanded to the entirety of the city, with the capital effectively on lockdown. Schools and public transit closed. NATO and the European Union, both of which are based in Brussels, found their operations disrupted. A reported 1,000 officers combed the city in search of Salah Abdeslam, a suspect in the Paris attacks. But the dragnet failed to ensnare Abdeslam, who would not be caught until March 18.

After that, officials eased up a bit on the visible enforcement. Local tourist authorities launched campaigns to convince would-be visitors that the capital was still safe and vibrant. At the same time, behind the scenes, Belgium was playing catch-up. The government worked to beef up its intelligence services, adding personnel and cash. The state’s intelligence community is believed to be smaller than those of its neighbors, accounting for size, despite the large jihadist problem, Reuters reported.

Some analysts blamed the overstretched capabilities of Belgian counterterrorism officials for not catching and disrupting the Paris plot, even though many of the attackers were known to be linked to terrorism and had had scrapes with the law before last November. Then, in the wake of the November lockdown, Belgian authorities “made a series of seemingly contradictory announcements about the security situation,” The Guardian reports. “Belgian security services appeared—despite the quality of many individual officials‚ overwhelmed. It was revealed that a few hundred agents were supposed to watch over thousands of potential militants. ‘We are simply exhausted,’ one senior security official said in an email.” Belgian security officials told BuzzFeed’s Mitchell Prothero that practically every possible detective and investigator in the country was detailed to investigating jihad.

But the problem is larger than simple staffing. Within Belgium, longstanding ethnic fractures create barriers to effective policing. And beyond Belgium’s borders, failures to share intelligence between European governments, and the staggering amount of intelligence noise related to possible terrorist plots, make policing extremely difficult.

First, there’s the domestic dynamic. Not unlike the Middle Eastern states set up after World War I, Belgium is a a fragile artificial creation, riven between French- and Flemish-speaking citizens. A consequently weak federal government and distrust among different law-enforcement authorities are said to impede communication, investigation, and apprehension of suspected terrorists. It is also unusually easy to acquire guns in Belgium compared to its neighbors.

Second, police agencies in different European countries do not cooperate effectively among each other. This creates special challenges, not only because terrorism is transnational but because Europe’s Schengen system makes it possible for people—including attackers—to cross borders with ease. Belgian officials had questioned some of the men involved in the Paris attacks prior to last November, but that information was never shared with French authorities. Since those attacks, European officials have been working to improve communication.

Finally, as Joscelyn noted, there’s so much information reaching counterterrorism officials that it’s nearly impossible to sort through it all. “You talk about chatter, there’s just too much of it now, so you have all these officials across the world that are trying to neutralize these persistent threats,” he said.

After months of relative quiet in Europe, there was suddenly fevered action on the terrorism front in mid-March. On March 15, police launched a raid in Brussels, apparently seeking Salah Abdeslam. After they came under fire, police shot and killed another man, who was later identified as Algerian Mohamed Belkaid. But Abdeslam once again escaped capture, although his fingerprints were detected in the raided flat.

Three days later, police finally caught up with Abdeslam, trapping and wounding him in Molenbeek. Foreign Minister Didier Reynders said the only remaining participant in the Paris attacks was cooperating with investigators. Then, on Tuesday, twin attacks at the airport and a metro station struck Brussels, with ISIS claiming responsibility.

Terrorism is an effective tactic around the world because it allows small groups of people to spread hysteria with relatively little manpower, and because it is impossible to prevent entirely, even in a police state. Where a devoted terrorist group exists, it is nearly inevitable its members will eventually succeed to some degree. But in Belgium, jihadists found a society that was unusually susceptible, and exploited it to bloody effect.