This chapter examines whether international relations, especially in an era of increasing globalization, are likely to be as violent in the future as they have been in the past. It asks whether globalization increases or decreases international security, which international relations theories best help to provide an understanding of global security and insecurity, and what are the most important contemporary threats to international security. The chapter first considers existing disagreements about the causes of war and whether violence is always likely to remain with us. It then discusses traditional/classical realist and more contemporary neorealist and neoliberal perspectives on international security, along with a range of alternative approaches. It also explores recent debates about globalization and geopolitics. Case studies in this chapter explore insecurity in the post-cold war world and tension in the South and East China Seas.