This document discusses the concept of national security and its primacy in foreign policy. It defines national security as protecting the survival of the nation-state from external threats. Realism theory views national security as the core objective of foreign policy. During the Cold War, national security dominated foreign policy agendas and led to the emergence of security studies. The document also examines different American grand strategies like neo-isolationism, liberal internationalism, and primacy that aim to achieve national security goals through different approaches to foreign involvement and military posture.