One of the central questions in work on terrorism's effectiveness is that of the most appropriate metric. If terrorism is conceptualised as a strategy to achieve substantive political change, it is largely ineffective. Assuming terrorism adheres to a strategic logic, it remains necessary to specify the mechanisms by which terrorism's effects are wrought, an area that is somewhat under-theorised. There is a growing consensus that terrorism is an unproductive method of forcing political change. Large-scale analyses have repeatedly demonstrated that terrorism does not reap political rewards. The chapter presents a clear picture of terrorism's political failure, and some of the factors that contribute to positive outcomes for militants. Militants are presumed to use five strategies: attrition, intimidation, provocation, spoiling, and outbidding. It is important to take account of the dynamic nature of political violence. Analysis of political violence is likely to reap the rewards of looking across political, organisational, social, and cultural effects.