International security, also called global security, refers to the amalgamation of measures taken by states and international organizations, such as the United Nations, European Union, Association of Southeast Asian Nations, and others, to ensure mutual survival and safety. These measures include military action and diplomatic agreements such as treaties and conventions. International and national security are invariably linked. International security is national security or state security in the global arena. With the end of World War II, a new subject of academic study focusing on international security emerged. It began as an independent field of study, but was absorbed as a sub-field of international relations. Since it took hold in the 1950s, the study of international security has been at the heart of international relations studies. It covers labels like “security studies”, “strategic studies”, “peace studies”, and others.