This Element addresses questions about social movement effectiveness and the strategies and methods that are most likely to achieve policy change. It examines the nature of peace movements through a comparative analysis of three major movements, focusing on their policy impacts. It assesses social movement dynamics and the mechanisms through which movements gain influence. The purpose is to mine campaign experiences from the past to develop action guidelines for more effective citizen activism against war and nuclear weapons in the future. The Element examines non-institutional and institutional forms of politics and the relationship between the two, and how they can be mutually reinforcing. It traces examples of inside-outside approaches within the three peace movements and their effects. Lessons from the analysis and case studies are applied in the final section to proposals for a new global freeze movement to stop the emerging international arms race.