The Islamic State (IS) [1], until 2014 a terror group little known outside of security circles, has fought its way up to the leadership position of the global jihadist movement. The terror group has achieved this feat within a very short period of time, ignoring the historic lessons learned from insurgencies around the world. Thus, the difficulty lies in explaining this rise against all odds and identifying the factors enabling IS to achieve this. In this series of articles, the author argues that there are at least four interrelated key factors, which were and continue to be central for the success of IS. The first one is the continuous recruitment of two groups of supporters.