John Herz was among the earliest to coin the concept of “security dilemma” and develop it into a theoretical framework. He used “domestic analogy” for international relations under anarchy, and was again the earliest to bring up systemic and structural factors of international relations studies. He emphasized that international relations do not have much to do with the goodness or evilness of human nature, as they hinge upon objective characteristics of international system. His theory thus parts away from the pessimistic prediction of classical realism that conflicts are inevitable and leaves much room for cooperation. Having analyzed the international system during the nuclear age, he further proposed the “nuclear dilemma” and “survival plight”—two subtypes of the “security dilemma”—and two corresponding measures—“holding operation” and “universalism”, which both offered solutions to traditional security problems and provided clues to contemporary untraditional security issues. After the end of the Cold War, there is a tendency to apply the theory of “security dilemma” to domestic politics in addition to its application in international relations. The concept of “security dilemma” has profoundly affected the research agenda and research domain of international relations theories.