This chapter describes the worldwide expansion of social movement activity in the twentieth century, paying attention to the intense relationship between political, social, and economic contexts and social movements. It uses international communism and the Soviet Union, the social movement wave of 1968, and 1989 to show how activists work to introduce social movements in authoritarian regimes but do not always succeed. The chapter explores the globalization of social movements, the role of changing technology, and the use of social movement forms by right-wing activists.