[1] Belgium has a population of 11 million including large numbers of immigrants from Muslim countries.
100,000 Moroccan citizens live in Belgium, often descended from Moroccans recruited to work in the mining industry in the 1960s; a small fraction of the children and grandchildren of the immigrant generation have been attracted to Militant Islamism and Jihad.
[3] In 2016, Belgian researcher estimated that about 562 individuals had travelled to become foreign fighters in the Syrian and Iraqi Civil Wars, the majority of whom joined the Islamic State with others joining the al-Qaida-affiliated group Al-Nusra Front.
The overall leader of that terrorist cell was believed to be Mohamed Belkaid, an Islamic State operative from Algeria who previously had lived in Sweden.
Salah Abdeslam was arrested a few days later and the surviving members of the cell, including brothers Najim Laachraoui and Khalid and Ibrahim Bakraoui (previously armed robbers) launched the 2016 Brussels bombings targeting Brussels airport and metro killing 32.