John Mearsheimer on War and International Politics

This article is a summarized version of the recent research paper by John J. Mearsheimer, published in International Security, Vol. 49, No. 4 (Spring 2025), pp. 7–36.

The post–Cold War era (1991–2017), known as the “unipolar moment,” was marked by the United States’ dominance as the world’s sole superpower. With the Soviet Union’s collapse, many believed that the age of great power wars had ended. But renowned realist scholar John J. Mearsheimer warns otherwise.

In his latest research, Mearsheimer argues that the world has entered a new multipolar age, marked by the rise of China and the resurgence of Russia. This shift has revived the potential for war among great powers, challenging the liberal belief that peace and cooperation had become permanent features of international politics.

Liberal Optimism vs. Realist Reality

Liberal theorists once celebrated the “end of history,” anticipating a peaceful world governed by liberal democracy and economic interdependence. But Mearsheimer challenges this narrative, asserting that it ignores the harsh realities of power politics.

He emphasizes that strategic and military considerations, not shared values or institutions, primarily shape interactions between major states. The return of U.S.-China-Russia rivalry signals that power struggles remain central to international affairs.

Politics: Conflict by Nature

Building on thinkers like Clausewitz and Carl Schmitt, Mearsheimer redefines politics as a competitive and often violent enterprise. Disagreements over governance, justice, or identity are not easily resolved—and when diplomacy fails, war becomes a logical extension of politics.

According to Mearsheimer, international politics is a high-stakes arena of survival, where mistrust, fear, and strategic interests outweigh cooperation and compromise.

The Anarchic World Order and the Security Dilemma

A core concept in Mearsheimer’s realist theory is anarchy—the absence of a global authority to enforce peace. In this environment, states act out of self-help, prioritizing survival.

This gives rise to the security dilemma: as one state builds its military to feel secure, others perceive a threat and arm themselves in response. The result is an endless cycle of mistrust, arms races, and potential conflict.

Even in peacetime, Mearsheimer argues, the threat of war is ever-present, guiding how states behave and how alliances form or break.

Law and Morality: Noble Ideas, Limited Power

Liberal ideals such as international law and just war theory seek to limit the use of force. Yet, in an anarchic system, no authority exists to enforce these norms. Mearsheimer believes that strategic interests often override legal or moral constraints, especially in times of crisis.

He points to Russia’s 2022 invasion of Ukraine as a preventive war—driven not by moral justifications, but by geopolitical calculation. Even moral theorists, like Michael Walzer, concede that in “supreme emergencies,” rules can be suspended. This, Mearsheimer argues, proves that survival trumps morality in the real world.

Nuclear Deterrence and Escalation Risks

While nuclear weapons have made total war less likely due to Mutual Assured Destruction (MAD), Mearsheimer warns that smaller conflicts still carry the risk of escalation.

Military logic often pushes for decisive action, and during wartime, political leaders may lose control. In a nuclear-armed world, one miscalculation can lead to catastrophe.

Strategic Cooperation: Real but Fragile

Mearsheimer does not deny that great powers can cooperate, especially on global issues like climate change or arms control. However, such cooperation is temporary and transactional, taking place under the shadow of strategic competition.

Alliances, he argues, are not rooted in shared values but in convenience and shifting interests. History shows that today’s friend can be tomorrow’s rival.

Morality as a Mask for Power Politics

States often use moral narratives to justify strategic actions. When strategic and moral aims align, governments present their wars as both necessary and just. But when they don’t, strategic interests prevail, and morality becomes a tool of persuasion.

Mearsheimer warns that equating all strategic decisions with moral virtue erodes the distinction between justice and self-interest. Realism, in contrast, acknowledges that moral values and political survival often diverge—and survival usually wins.

Conclusion: War as a Permanent Reality

In closing, Mearsheimer reminds us that war remains a central feature of international relations, especially in an era of multipolarity. While international law, morality, and cooperation have roles to play, they are subordinate to the logic of power and survival.

The realist perspective he offers is not comforting—but it is sobering. It challenges us to view global politics through the lens of strategic competition, rather than through utopian ideals.