Why do realists consider state survival the most important national interest?

In the study of international relations, realists consider state survival the most important national interest because they operate under the fundamental assumption that the international system is characterized by anarchy.

In this anarchic environment, there is no central authority or suprastate power capable of enforcing international law or arbitrating disputes between sovereign states. Because states cannot rely on external protection, they exist in a self-help regime where they must depend entirely on their own capabilities and power to ensure their security, political system, and territorial integrity.12

Realists argue that because the system lacks enforceable rules of conduct, the threat of violence is constant. Consequently, survival is the prerequisite for all other national goals, such as economic prosperity or cultural preservation. Without ensuring its own existence first, a state cannot pursue any other interests in a world where power-maximizing behavior is the norm and conflict is an inherent possibility.12