John J. Mearsheimer (born 1947) is the R. Wendell Harrison Distinguished Service Professor of Political Science at the University of Chicago and the most influential contemporary theorist of structural realism. His central work, The Tragedy of Great Power Politics (2001, updated 2014), advanced the doctrine of offensive realism, which holds that the anarchic structure of the international system — the absence of any supranational authority above states — compels great powers to maximise relative power rather than merely balance against threats. This distinguishes him from the defensive realism of Kenneth Waltz (Theory of International Politics, 1979), who argued that states seek only enough power for security. For Mearsheimer, uncertainty about others' intentions and the survival imperative drive states to pursue regional hegemony, the only achievable status given that oceans act as "stopping power" preventing global domination.
Mearsheimer's theory rests on five bedrock assumptions: the system is anarchic; great powers possess offensive military capability; states can never be certain of others' intentions; survival is the primary goal; and states are rational actors. From these he deduces that great powers fear one another, aim to be the most powerful state in their region, and seek to prevent rival hegemons elsewhere — the logic underpinning the United States' historical opposition to peer competitors in Europe and Asia. He applied this framework controversially in The Israel Lobby and U.S. Foreign Policy (2007, with Stephen Walt), arguing that domestic lobbying distorted American strategic interest, and in his persistent warnings that NATO enlargement would provoke Russia, a thesis revived after the 2014 Crimea annexation and the 2022 invasion of Ukraine. In The Great Delusion (2018) he attacked liberal hegemony and democracy promotion as strategically self-defeating.
In the 2026 strategic landscape, Mearsheimer is best known for his prediction that the United States and China are locked in an intensifying security competition, possibly the most dangerous great-power rivalry of the century, because a rising China will inevitably seek to dominate Asia as the U.S. once dominated the Western Hemisphere. His insistence that liberal institutions and economic interdependence cannot override structural pressures places him in direct opposition to liberal-institutionalist scholars such as Robert Keohane and Joseph Nye, and to constructivists like Alexander Wendt, whose "anarchy is what states make of it" thesis Mearsheimer rejects. His "China cannot rise peacefully" argument is a standard reference point in debates on the Indo-Pacific and the Thucydides Trap.
For exam purposes, Mearsheimer appears in International Relations theory sections (UPSC Political Science & IR optional, FSOT, CSS IR paper) wherever realism is tested. Candidates must distinguish offensive realism (Mearsheimer) from defensive realism (Waltz) and classical realism (Morgenthau, Carr), and be able to contrast the realist paradigm with liberalism and constructivism. Typical question angles ask candidates to apply offensive realism to US-China relations, NATO expansion and Ukraine, or to critically evaluate whether structural determinism adequately explains state behaviour. A strong answer names The Tragedy of Great Power Politics, the five assumptions, the concept of regional hegemony, and the offensive-versus-defensive realism debate.
Example
In a March 2022 lecture circulated widely after Russia's invasion of Ukraine, John Mearsheimer reiterated his 2014 thesis that NATO's eastward expansion bore primary responsibility for provoking Moscow.
Frequently asked questions
Waltz argued states seek only enough power for security and that excessive expansion is punished by balancing. Mearsheimer argues the anarchic system compels great powers to maximise relative power and pursue regional hegemony, because survival can never be guaranteed by moderation.