Thucydides Trap

The tendency for a rising power to provoke fear in an established power, increasing the risk of conflict between them. The term modernizes Thucydides’ account of the causes of the Peloponnesian War.

Power transition theory: A theory that war becomes more likely when a rising state approaches or challenges the dominant state. It formalizes the power shift at the heart of the trap.
Thucydides: An ancient Greek historian whose account of the Peloponnesian War shaped the study of political conflict. His explanation of the war supplied the metaphor’s central claim about fear and power.
Anglo-German naval arms race: A pre–World War I competition between Britain and Germany to build naval power. It shows how a rising state’s military buildup could alarm an established maritime power.
Democratic peace theory: The theory that democracies rarely fight wars against one another. It highlights how political institutions may restrain conflict despite shifts in power.
Security dilemma: A situation in which one state’s defensive measures make other states feel less secure. Mutual attempts to reduce vulnerability can intensify fear between the powers.
Peloponnesian War: A war between Athens and Sparta and their allies, fought from 431 to 404 BCE. Thucydides used the conflict to illustrate how Athenian growth frightened Sparta.
Rise of the United States: The nineteenth- and early twentieth-century expansion of U.S. economic and military power. Its largely peaceful rise challenges claims that power transitions inevitably produce war.
Offensive realism: A theory that states seek regional dominance because uncertainty makes power the surest route to security. It explains competition through enduring incentives, not just a particular transition.
Preventive war: A war launched to prevent an adversary from becoming more powerful in the future. A declining power may see war as preferable to facing a stronger rival later.
History of the Peloponnesian War: Thucydides’ unfinished historical account of the conflict between Athens and Sparta. Its opening explanation is the ancient source most often invoked by the trap.

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