The previous chapter showed two things: first that terrorism usually occurred when the political system was unresponsive or hostile to the concerns of certain groups, and second that each and every wave of terrorism was associated with the existence of a body of sympathizers and supporters. The closest association appeared to be between organizational mobilization (i.e. the number who participate in some extremist movement) and terrorist violence. In the first section of this chapter, the relationship between terrorist violence and the organizational growth and decline of extremist movements will be examined in more detail.