The spectacular attacks on New York City on 11 September 2001 carried out by 19 suicide bombers belonging to the al-Qaeda network kicked off the century. Other, more recent attacks in different European cities, this time claimed by the Islamic State, have made terrorist acts daily news across the globe. Despite the differences in organization (a network such as al-Qaeda or grouped by territories such as Islamic State), these youth, engaged on the path of violence in the name of jihad, are guided by the force of the singular narrative of membership in the Ummah, the world-wide Muslim community, that lends all its strength to the appropriation of an ideology and the transition to violence...