This chapter examines the impact of the growth of multilateral and transnational governance on sovereignty and the diffusion of political authority. 1 It begins by exploring the legacy of World War II and the building of the UN system. The rise of intergovernmentalism and transnational governance arrangements are examined, followed by an assessment of some of the leading changes in the postwar global politics landscape. These issues are explored in greater depth across two cases: Security and the environment. The chapter concludes by drawing together the threads of the discussion.