This monograph culls major insights from rational choice scholars about the requirements for successful terrorism groups and the motivations of individuals who join those groups. Successful terrorist groups are defined as those that are both durable and pernicious. The rational choice research insights are applied to three historical cases of ‘successful’ violent extremist groups where religion was not a primary terrorist inspiration, and where the groups were not from a Muslim country — highlighting the fact that terrorism and violent extremism are not just a phenomenon afflicting Islam. The monograph turns to application of the insights from rational choice study of successful terrorist groups to assess the purported ‘success’ of the Islamic State of Iraq and Syria (ISIS), or Da’esh, concluding that it is far too early to say that this terrorist outfit will become both durable and pernicious. It concludes while advancing several ways in which all countries, including those in the GCC, might best counter the factors contributing to the development and sustainment of successful terrorism and violent extremism.