The Palestinian editor of Rai al-Youm offers a comprehensive review of the group’s organisational structure and leadership, strategies, tactics and diverse methods of recruitment. He traces the salafi-jihadi lineage of IS, its ideological differences with al-Qa’ida, and the deadly rivalry that has emerged between their leaders. Atwan also shows how the group’s rapid growth has been facilitated by its masterful command of social media platforms, the ‘dark web’, Hollywood ‘blockbuster’-style videos, and even jihadi computer games, producing a powerful paradox where the ambitions of the Middle Ages have re-emerged in cyber-space.