The Balance of Power

In brief

Imagine a schoolyard with no teacher. If one child grows big enough to bully everyone, the others do not submit one by one. They gang up. That, scaled to nations, is the balance of power: in a world with no government above states to keep order, states guard against being dominated by whoever is becoming too strong. They do it in two ways. They arm themselves (internal balancing), or they form alliances with others who share their fear (external balancing). Across four centuries of European history, again and again, a coalition assembled to stop the strongest power of the day: the Habsburgs, then Louis XIV's France, then Napoleon, then Wilhelm's and Hitler's Germany. The idea is claimed both as a description of what states tend to do and as a prescription for what prudent statesmen should do.

The full treatment

The problem it answers

The problem is anarchy, in the technical sense the field uses: not chaos, but the absence of any authority above sovereign states. Inside a country, a citizen who is threatened can call the police; there is a government with a monopoly on legitimate force. Between countries there is no such body. The United Nations is not a world government, and it cannot compel a great power. So each state is ultimately responsible for its own survival, a condition realists call self-help. If that is your situation, the worst thing that can happen is for one state to become so powerful that it can dictate to all the others, or conquer them outright. Universal empire, in this view, is the standing danger. The balance of power is the mechanism by which that outcome is, most of the time, prevented.

How it works

Balancing takes two forms, a distinction sharpened by Kenneth Waltz. Internal balancing is what a state does by its own efforts: raising taxes, expanding its army, building weapons, growing its economy so it can afford all of the above. External balancing is done through others: forming alliances, pooling capabilities, and coordinating so that the combined weight of the coalition exceeds that of the state it fears. A weak state has little internal capacity and must rely on allies; a great power can often balance largely from its own resources. The result, when balancing works, is that no single power can overwhelm the rest, because any bid for dominance triggers a counterweight.

The logic does not require anyone to intend the balance. Waltz's key move in 1979 was to argue that balances form whether or not statesmen are trying to create them, the way prices emerge from a market without anyone setting them. States pursuing nothing but their own security, under anarchy and among many actors, tend to produce a rough equilibrium as a byproduct. This is why the theory claims to be structural: the pressure comes from the shape of the system, not from the character of leaders.

The alternatives it is defined against

Balancing is only one possible response to a rising power, and it is best understood alongside the others. The first alternative is bandwagoning: instead of opposing the strong state, you join it, hoping to share in the spoils or at least avoid being crushed. Balancing and bandwagoning are the two poles, and much of the theory's interest lies in explaining when states do which.

The second alternative is buck-passing, emphasized by John Mearsheimer. Balancing is costly and dangerous, so a threatened state may try to get someone else to bear the burden of confronting the aggressor while it stays safely on the sidelines. Britain and France passing the buck to each other, and both hoping the Soviet Union would absorb Hitler, is the textbook case from the 1930s. Buck-passing can leave a coalition dangerously late and underprepared, which is one reason balancing sometimes fails to happen in time.

The refinement that matters most

The single most important revision came from Stephen Walt in The Origins of Alliances (1987). Walt noticed that states do not, in fact, reliably balance against raw power. In the Cold War, most of the world's strength did not gather against the United States, even though America was the most powerful state. Walt's answer was that states balance against threat, not against power as such. Threat is a compound of aggregate power, geographic proximity, offensive capability, and, crucially, perceived intentions. A powerful state that others see as benign draws little balancing; a weaker state seen as aggressive and nearby draws a great deal. This balance of threat theory explains why allies flocked to the distant, status-quo United States rather than uniting against it, and it remains the most durable amendment to the original idea.

Lineage

The practice is far older than the theory. Thucydides, in the fifth century BCE, described the Greek city-states aligning against a rising Athens. The phrase itself became common in Renaissance Italian diplomacy among the shifting alliances of the city-states, and it entered the vocabulary of European statecraft in the seventeenth and eighteenth centuries. The Peace of Utrecht in 1713 explicitly invoked an "equilibrium of power" as its goal.

The classic theoretical statement is David Hume's essay "Of the Balance of Power" (1752), which argued that the principle was known to the ancients and was a matter of common prudence rather than modern invention. In the twentieth century the idea became the centerpiece of political realism. Hans Morgenthau, in Politics Among Nations (1948), treated it as an almost permanent feature of politics wherever independent units interact. Kenneth Waltz, in Theory of International Politics (1979), stripped it down to a structural theory that made balancing the expected outcome of anarchy itself. From there the concept branched: Walt added the balance of threat, Mearsheimer added buck-passing and the drive toward regional hegemony, and Randall Schweller reopened the study of bandwagoning. It descends from the broader tradition of realism and rests on the prior assumption of sovereign states in an anarchic system.

The strongest case for it

The historical record is the strongest evidence. For roughly four centuries, no state managed to conquer Europe, and each serious bid for dominance was defeated by a coalition of the rest: the Habsburg empire, the France of Louis XIV, revolutionary and Napoleonic France, and Germany in two world wars. The pattern is hard to explain by accident. Something recurrent was pushing rivals together against whoever led, and the balance of power names that something.

The theory is also parsimonious and general. It does not depend on the ideology, religion, or personalities of the states involved; it predicts the same alignment behavior from ancient Greek cities, early modern monarchies, and modern republics. A theory that explains so much from so little has real power. And as prescription it offers concrete guidance: a prudent statesman watches for concentrations of power and works to offset them before they become unmanageable, which is exactly the counsel Hume drew and much of European diplomacy followed.

The strongest case against it

The most serious empirical challenge comes from the historian Paul Schroeder. In "Historical Reality vs. Neo-Realist Theory" (1994) he examined the actual diplomatic record and argued that states frequently did not balance. They hid, they bandwagoned with the stronger side, they specialized in narrow tasks, they appealed to great-power protectors, and they sometimes joined the very power that threatened them. The tidy story of coalitions forming against every rising power, Schroeder argued, is imposed on a messier history than the theory admits.

A second, harder problem is unipolarity. If balancing were as automatic as Waltz claimed, the collapse of the Soviet Union in 1991 should have produced a swift coalition against the sole surviving superpower. It did not. William Wohlforth, in "The Stability of a Unipolar World" (1999), argued that a large enough gap in power can be self-sustaining, because balancing against a dominant state looks futile and provokes the very hostility it is meant to guard against. The absence of hard balancing against the United States for two decades is a direct embarrassment to the strong form of the theory, and it drove scholars to weaker notions like "soft balancing," which critics regard as a stretch.

Randall Schweller pressed a related point in Deadly Imbalances (1998) and later work: the theory is biased toward balancing and treats bandwagoning as an anomaly, when in fact states often join rising powers for profit, not just for safety. And from outside realism, liberal and constructivist scholars argue that the whole framework mistakes a specific historical practice for a law of nature. Institutions, shared democratic norms, and economic interdependence can channel rivalry into means other than counter-alliances, so that the balance of power describes one world, not the human condition.

Where it stands now

The balance of power remains a central concept of international relations, but no longer an unquestioned law. Its structural, automatic version, associated with Waltz, is widely regarded as too strong, undercut by the long unipolar moment after the Cold War. Walt's balance of threat is the more resilient formulation and is still routinely used. The concept has returned to prominence in debates over the rise of China and the response of the United States and its Asian partners, where the vocabulary of balancing, bandwagoning, and buck-passing structures much of the analysis (see the-thucydides-trap for the specific worry about power transitions). The honest verdict is that states often balance, that they do not always balance, and that the interesting questions are now about the conditions under which they do.

Test yourself

Think of a rising power today that worries its neighbors. Are those neighbors building up their own forces, forming alliances against it, quietly joining it, or waiting for someone else to act? Name which of the four responses (internal balancing, external balancing, bandwagoning, buck-passing) each is choosing, and ask what that tells you about whether they fear the power itself or its intentions.