Every theory in this course talks about power, but power is surprisingly hard to pin down. This level looks at what power is, how states respond to the power of others, and how they try to prevent attacks without fighting.

What is power?

The political scientist Robert Dahl defined power in 1957 as a relationship. In Dahl's definition, A has power over B to the extent that A can get B to do something B would not otherwise do. That definition is a reminder that resources are not the same as results. The United States had overwhelming military superiority in Vietnam and still failed to reach its goals. Scholars usually measure resources anyway, through economic output, population, military spending and technology, because they are easier to count than outcomes.

Joseph Nye added a distinction in 1990. Hard power works through coercion and payment, the familiar sticks and carrots. Soft power is the ability to get what you want through attraction rather than force or payment: through a country's culture, its political values and policies that others see as legitimate. Critics reply that soft power is hard to measure and easily overstated. Nye's answer is that attraction becomes visible when others follow a country's lead without being forced or paid.

The balance of power

The balance of power is among the oldest ideas in diplomacy. When one state grows threatening, others have two basic options. Balancing means arming or joining with others to oppose a rising or threatening power, while bandwagoning means joining the stronger or more threatening side. Realists expect balancing to be the more common response, because siding with the strongest leaves you at its mercy. Britain followed this logic for centuries, opposing whichever continental power, whether Spain, France or Germany, came closest to dominating Europe. As Lord Palmerston told Parliament in 1848, "We have no eternal allies, and we have no perpetual enemies. Our interests are eternal and perpetual."

Stephen Walt refined the idea in 1987. States, he observed, balance not against power as such but against threat. Walt's balance of threat theory holds that states weigh another state's power, its nearness, its offensive capabilities and its apparent intentions. That explains why most of Western Europe allied with the United States, the stronger superpower, against the Soviet Union, the nearer and more threatening one.

Shifts in power can be dangerous too. A. F. K. Organski's power transition theory (1958) holds that great war is most likely when a rising challenger nears the strength of the leading state, a dissatisfied newcomer meeting a guardian of the old order. In 2017 Graham Allison popularized the idea under Thucydides' name and counted war in 12 of 16 cases where a rising power challenged a ruling one since about 1500, a count other historians dispute.

Alliances and their dilemmas

An alliance is a formal promise of military support. Alliances add strength, but they create a dilemma described by the political scientist Glenn Snyder in 1984. Allies fear abandonment, being left alone when help is needed, and entrapment, being dragged into a partner's war. Holding a partner close reduces the first risk and raises the second, so every alliance involves a constant balancing act among its own members. The road to the First World War is the classic case of entrapment.

Deterrence and compellence

The general point here comes from the economist Thomas Schelling's Arms and Influence (1966). Deterrence aims to stop an opponent from starting something. Compellence uses threats to make an opponent stop something it is already doing, or undo it. Schelling argued that compellence is usually harder, because giving in is visible and humiliating, while not attacking can be explained away. Both depend on credibility: the other side must believe the threat will be carried out.

Extended deterrence is one state's promise to defend an ally as if it had been attacked itself. It is the hardest kind of threat to make credible, since the defender must seem willing to risk its own cities for someone else's.

Worked example: Finland and Sweden join NATO

For decades after 1945 Finland stayed outside military alliances and kept careful relations with Moscow. Sweden had avoided alliances for about two centuries. Russia's full-scale invasion of Ukraine in February 2022 changed both calculations within months. Finland joined NATO in April 2023, and Sweden in March 2024.

The concepts of this level sort out the choice. Russia's raw power had not suddenly grown; if anything, its army was being worn down in Ukraine. What changed was its perceived intention, which is Walt's point that states balance against threat rather than power. Finland, with a land border with Russia of roughly 1,300 kilometers, chose to balance rather than bandwagon. Ukraine's fate made the risk of abandonment vivid, since a state outside an alliance might face an attack alone. Some critics in both countries worried about entrapment instead, and Russia called the move provocative, an illustration of the security dilemma from level 2. A constructivist would add that a long-settled national identity, neutrality, gave way remarkably fast once threat perceptions shifted.