This document discusses the history and development of security studies as a sub-discipline of international relations. It covers the key assumptions and paradigms of security studies, including the realist, rationalist, and revolutionary traditions. The document then outlines the periodization of security studies, covering developments from the inter-war period through post-Cold War debates around conceptualizing security. Key topics discussed include the rise of nuclear weapons and deterrence theory, declines in security studies during détente, and expanding notions of security to include human and environmental dimensions.