The subject of this book is complex, but the argument is fairly simple. My objective is to study how a set of related political ideologies, born of the peculiar histories of Islamisation and colonisation in the Sahel-Sudan, endeavour to transform state and society in that region by resorting to methods of persuasion and of violence. These modern ideologies are all forms of Salafi radicalism, and the objective I just mentioned is grounded in the claim that, by studying and understanding Salafi radicalism as their political matrix, we can better understand the nature of their appeal, their strengths and their limitations, and we can also be better able to peer into their future. Moreover, an important implication of this claim is that Salafi radicalism is a political doctrine and must be analytically distinguished from Salafi theology, which provides it with its religious discourses and procedures of legitimation in prevailingly Muslim contexts, but which is not a political doctrine in itself, a point which I revisit below. Salafi radicalism exists in the five countries that today share the geographic and cultural space generally referred to as ‘the Sahel’ – although it may be more accurately called ‘the western and central Sudan’, or ‘the West African Sudan’ – all phrases which will be used throughout this work. This book identifies and compares the ideologies of Salafi radicalism within these countries on the basis of a number of theories, explanatory concepts and parameters, and methods of analysis, all of which will be presented below.