Last week, terrorists bombed multiple locations in Brussels, claiming at least 31 lives and making Belgium the latest flashpoint in a wave of attacks across Europe. We’ve compiled some of the best reporting on the recent attacks in Brussels, why Belgium has become a prime location for terrorists, and how the threat in Europe has grown over the years. See anything we missed? Leave suggestions in the comments.

Terrorism Response Puts Belgium in a Harsh Light, New York Times, November 2015
Before the Paris attacks, the mayor of Molenbeek, a district in Brussels, was given a list of suspected terrorists that included the names of two brothers who took part in the Belgium attacks. When asked about the list, the mayor said, “It is not my job to track terrorists.” And she’s right. The New York Times examines the “labyrinthine pathways that connect and also divide a multitude of bodies responsible for security in Brussels.”

More: Since Paris, there have been hundreds of terror attacks

Europe’s Revolving Door Prisons Compound Growing Terror Threat, ProPublica, June 2015
Even when Europe catches suspected terrorists, it’s not good at keeping them locked up. “[I]n Belgium, prison is like a hotel,” complained the mother of a convicted jihadist. Sebastian Rotella examines how Europe’s sentencing policies have yet to adapt to the current threat of terrorism within its borders.

Al-Muhajiroun’s European Recruiting Pipeline, Combating Terrorism Center at West Point, August 2015
The Al-Muhajiroun jihadist group, formed in Europe in 1996, has been implicated in several terror plots and spawned similar branches throughout Europe over the last decade. Now, according US terrorism experts, there is a growing consensus among European counterterrorism officials that the group “plays a role in networks that provide new recruits to fight in Syria and Iraq”.

ICSR Insight – German Jihadists in Syria and Iraq: An Update, International Center for the Study of Radicalization and Political Violence/King’s College London, February 2016
Germany has become a “considerable source of Islamist foreign fighters” that have sworn their allegiance to ISIS, according to this ICSR analysis. As of this report, there were “more than 800 people who left Germany for Syria and Iraq since the beginning of the Syrian conflict.”

More: Foreign Fighters in Syria/Iraq now exceeds 20,000; surpasses Afghanistan conflict in the 1980s

Europe’s converts to Islam hearing the call to jihad, Washington Post, May 2015
Muslim communities are under a microscope as the Islamic State expands its recruiting efforts across the West. But as many as 1 in 6 Europeans who join ISIS are converts from “non-Muslim” faiths who, according to one imam, “are the most vulnerable [to radicalization] because they do not yet fully understand Islam.”

Jihad and Girl Power: How ISIS Lured 3 London Girls, The New York Times, August 2015
According to one estimate, more than 550 women and girls are among the 4,000 Westerners who’ve made the journey to Syria and Iraq to join ISIS. Since women are not allowed to become fighters, many of them become “wives, mother’s, recruiters, and sometimes online cheerleaders for violence.” The New York Times traces the path of three London girls who traveled to Syria, attracted by an ISIS strategy that employs “ girl-to-girl recruitment strategies, gendered imagery and iconic memes”.

How Belgium Became a Terrorism Hotbed, The Daily Beast, November 2015
The links “between jihadist operations and Belgian terrorist cells” are being uncovered with increasing frequency. This article provides a timeline of the most recent attacks in Western Europe and their relation to Belgium and its terror cells.

Trail of Paris Attackers Winds to Terrorism’s Longtime Outpost, ProPublica, November 2015
The suspected mastermind behind the Paris attacks was killed in a pre-dawn raid in the Saint-Denis suburb of Paris, but his roots point to an often-discussed trend in counterterrorism circles: “the shadow Belgium casts over the terror threat in Europe.” According to a commandant of the French national police, “Things are easier for terrorists in Belgium than they are in France. They use Belgium as an outpost.”

Paris Attacks Highlight Jihadists’ Easy Path Between Europe and ISIS Territory, New York Times, November 2015
When “the attack that everyone was worried about” happened, it highlighted law enforcement’s inability to monitor the influx of young European Muslims radicalized by ISIS; at least six of the suspects in the Paris attacks had returned to Europe after fighting in Syria. “There are so many individuals and cases they are worried about by now, historic and current, that they cannot keep up,” said one expert.

More: Unraveling the Connections Among the Paris Attackers

On ISIS

How ISIS Works, The New York Times, September 2014
ISIS has a very complex governing structure. This is an overview of the terrorist groups its organizational make-up as well as how ISIS has expanded its territory in Iraq and Syria through violence and the strategic takeover of oil assets.

Watch: a 6-minute history of ISIS, Vox, March 2016

The rise of ISIS didn’t begin in the Middle East with Iraq and Syria, but in Afghanistan. This video traces ISIS’ history from its roots with Abu Musab al-Zarqawi in the late 70’s through the present.

More: What Russia’s military proved in Syria

Inside Isis Inc: The journey of a barrel of oil, Financial Times, October 2015
Crude oil is the biggest single source of revenue for ISIS. This Financial Times’ special report details how ISIS finances its terror operations, who profits, and why it’s difficult to disrupt.

What ISIS Really Wants, The Atlantic, March 2015

Western leaders make ‘dangerous decisions’ regarding ISIS due to a misreading of the fundamental differences between ISIS and al-Qaeda, Graeme Wood writes in this exploration of the origins and religious ideology of ISIS.

More: Religious scholar on the ‘phony’ Islam of ISIS

This article first appeared on Pro Publica.