The security dilemma describes a situation in international relations where states' efforts to enhance their security may inadvertently increase tensions and conflict, even when their intentions are defensive. This phenomenon arises because states interpret defensive measures by others as potential threats, leading to arms races and the risk of war due to the anarchic nature of global politics. Historical examples, such as the Peloponnesian Wars, demonstrate how power dynamics, fear, and misperceptions can escalate conflicts between states.