The origins of the First World War have played an important role in the development of international relations theory, helping to inspire the principal concept in structural realist theory: the security dilemma. The security dilemma explains how states with fundamentally compatible goals, namely security, nevertheless end up in competition and war. This happens when the power a state acquires for security can “render others more insecure and compel them to prepare for the worst.”2 That is, a security dilemma exists when the capabilities a state builds for its own defense and security decreases the security of others.3 These states respond in kind with military buildups of their own, the result of which is an action-reaction spiral that leads to security competition and sometimes war. The central insight of security dilemma theory is that states pursuing nothing more than security and self-defense can end
up acting as if they are aggressors, creating a self-fulfilling prophesy of competition and insecurity.