Concept and difference from preemption
Levy (1987) described the preventive motivation as that of a state whose relative power is declining and which, fearing it will have to fight or concede under worse conditions later, prefers to fight while it still has the advantage. Because preventive war responds to long-term power shifts over years, it differs from preemption, in which a state strikes first in the belief that an enemy attack is imminent. Preemption may be justifiable as self-defense under international law, but preventive war, begun before a threat has materialized, is considered much harder to justify. Thucydides' explanation of the Peloponnesian War as caused by the growth of Athenian power and the fear it inspired in Sparta is often cited as an old example of the preventive motive.
A rationalist explanation: commitment problems
Fearon (1995) argued that because war is costly, rational states should in principle prefer bargaining to war, and he identified commitment problems as one reason war nonetheless occurs. A rising state can promise concessions now, but once it becomes stronger it has an incentive to break those promises. Unable to trust such promises, a declining state may choose to fight now to avoid future disadvantage. Powell (2006) showed that such commitment problems lead to war when the distribution of power shifts by a large amount and rapidly. Van Evera (1999) analyzed how the opening and closing of military windows of opportunity raise the risk of preventive war. This discussion is closely tied to power transition theory and the Thucydides trap.
Democracies and historical cases
Schweller (1992) argued that democracies, even when declining, tend to choose alliances or accommodation rather than preventive war. Levy (2008), by contrast, pointed out that democracies have repeatedly launched or seriously considered preventive wars and concluded that democracy's restraining effect is limited. Trachtenberg (2007) analyzed how in the early Cold War some in the United States argued for preventive war before the Soviet Union acquired nuclear weapons, and how the 2003 Iraq War was justified by a preventive logic of eliminating a weapons of mass destruction threat in advance. Preventive war is thus studied as a form of war that emerges when power shifts, uncertainty and problems of trust overlap.
FAQ
- What is the difference between preventive war and preemptive war?
- A preemptive strike is launched when an enemy attack is clearly imminent, while a preventive war is fought when there is no immediate threat, to stop a rival from becoming stronger in the future. Because the threat has not yet materialized, preventive war is harder to justify.
- Why is it hard to prevent preventive war through bargaining?
- Because a rising state that promises concessions now may break them once it becomes stronger. A declining state cannot easily trust such promises and may decide it is better to fight while it still has the advantage. This is called a commitment problem.
Sources reviewed: 2026-10-26
References
- Levy, J. S. (1987). Declining power and the preventive motivation for war. World Politics, 40(1), 82–107. The standard conceptual treatment of the preventive motivation — the place to start.
- Fearon, J. D. (1995). Rationalist explanations for war. International Organization, 49(3), 379–414. The rationalist starting point: commitment problems explain why bargaining fails to prevent preventive war.
- Powell, R. (2006). War as a commitment problem. International Organization, 60(1), 169–203. Formalizes how rapid power shifts create commitment problems — for deeper study.
- Schweller, R. L. (1992). Domestic structure and preventive war: Are democracies more pacific? World Politics, 44(2), 235–269. Argues democracies rarely wage preventive war — regime type and prevention.
- Levy, J. S. (2008). Preventive war and democratic politics. International Studies Quarterly, 52(1), 1–24. Revisits Schweller and shows democracies have waged preventive wars — compare the two views.
- Trachtenberg, M. (2007). Preventive war and U.S. foreign policy. Security Studies, 16(1), 1–31. A historical look at preventive war thinking in U.S. policy from the Cold War to Iraq — real cases.
- Van Evera, S. (1999). Causes of War: Power and the Roots of Conflict. Ithaca, NY: Cornell University Press. Analyzes windows of opportunity and preventive war among the main causes of war — useful for comparison.