The balance of power is historically one of the most important concepts of international politics and the academic discipline of international relations (IR). “No other single proposition about international politics,” Brooks and Wohlforth write, “has attracted more scholarly effort than the balance of power. It is perhaps as central in today's thinking as it has been at any time since the Enlightenment” (2008: 7). Michael Sheehan labels it “one of the most important concepts in history” (1996: 1).

Whilst diplomats and politicians throughout history have used the balance-of-power concept in many different circumstances and for many different purposes, the concept is also a theory of international politics used by scholars to explain phenomena in the world around us today. Normally, scholars take its main logic to be the following: if there is a rising, big, and powerful state in the international system, other smaller states may find this Great Power threatening and will therefore join together to oppose and to balance it, to achieve an equal weight in the weighing scales. However, should one of the smaller states initially banding together itself grow too large for comfort, the remaining small states might join in a new alliance – perhaps even together with the initially big and powerful state – to balance out the new threat. The balance of power may therefore be shifting over time, as states form new coalitions responding to new threats and developments within or between states.

The above is what balance-of-power theorists expect to happen in international politics, also because traditional balance-of-power theory assumes that states will always put their own interests first, including the very survival of the state. States operate in an anarchical environment, meaning that any and every state is in principle on its own; there is no global emergency phone number to call when trouble arises. Therefore, states must increase their own power to counter actual and potential threats from other states.

Scholars of international politics therefore take the balance of power to be a mechanism that ideally would make states intentionally or unintentionally join the weaker part against the strong, to equal out or balance the distribution of power amongst states in the international system. They would do this to assure their own survival for fear of being usurped by a dominant state. When every state acts this way, a balance of power emerges where no state is predominant, and therefore no large-scale war will take place. The result is a stable international system of states, although shifts in the balance could result in instability, even war.

This is a standard definition, but the concept of a “balance of power” has been used in multiple ways with many different meanings. For example, it could simply be a definition of how international politics stands at a specific moment, meaning the current distribution of power – the status quo – whether it is in balance according to the above definition or not. For example, one could talk about “the balance of power in Europe” at a particular point in time. It can also be a policy prescription, something successful policy-makers should pursue. The balance of power can also be an ideology, just like any other political view, or be used as propaganda to sway a public in one or the other policy direction.

What is certain is that the balance of power has been at the center of debate in academic IR. Three central IR publications on the modern concept of the balance of power – by Hans Morgenthau, Hedley Bull, and Kenneth Waltz – are flanked by an array of writings on the concept, debating such issues as whether it promotes peace or war, whether it is European or also extra-European, if there is one balance or also various sub-balances; also, the connections between balancing and deterrence, the balance of power as a mechanical–structural system or as intentional foreign policy prescription, whether it guarantees the independence of all states or only of the “Great Powers,” to mention only some.

What all of these debates have in common is that they consider the balance of power as one of our theories of international politics. A theory is a tool that academics and scholars use to simplify and isolate parts of reality, to make it easier and more manageable to study. The balance of power is one theory of how international politics work, and how states interact.

To show how balance-of-power theory is useful and warranted, scholars often refer to historical examples of how the balance of power has been operating. Another reason for referring to history, however, is that academics today are not the only ones who have been using the balance of power, or even invented the theory, to make sense of the world. In addition, for hundreds of years, diplomats and politicians, who are not necessarily scholars or trained academically, have also been using the balance of power to make sense of their world. So whilst the balance of power is an abstract concept that allows a depiction of the general patterns of international politics, it has also been used to formulate foreign policy and make diplomatic maneuvers. The history of the balance of power is therefore also important in and of itself and adds to our historical understanding of diplomacy. That is, the balance of power is both a theory used by us – students and professional scholars – and a concept used by people in very different times and circumstances, including many diplomats. For the study of practical diplomacy, the latter part is what would interest us the most. Therefore, the first part below concerns how diplomats in former times have been using the concept, whilst the second briefly considers contemporary debates about the balance of power as a scholarly theory of international politics.

The Balance of Power in History

It is in realist theories of international relations that we most often encounter the concept of the balance of power. Simply put, realist theories claim that when it comes to the most fundamental principles of international politics, the world is the same now as it was thousands of years ago. There are certain constants of international politics and one, they claim, is the balance of power. Accordingly, we should expect to find the balance of power expressed throughout much of recorded history.

Scholars even claim to find the idea of the balance of power among the ancient Greeks, in the Athenian historian Thucydides's account of the Peloponnesian War from 431 bce. Thucydides did not write about the “balance of power,” but some argue that there might have been a balance-of-power thinking, without the exact phrase being deployed. This, however, is difficult to ascertain. What is true is that the Italian diplomat and writer Niccolò Machiavelli in the 1480s talked about the importance of the relations of strength between the Italian city-states of the period. Some have argued that Italy in the fifteenth century was based on a balance-of-power system where the city-state of Florence and its ruler Lorenzo de Medici balanced against the Republic of Venice. Whilst Machiavelli might not have developed a concept of the balance of power that we would recognize, at least he conceived that, in addition to “domestic” politics in each city-state, the relations between states were of importance for their security.

Thucydides and Machiavelli did not explicitly mention the balance of power, although their writings are seen to represent the balance-of-power idea, as David Hume argued in 1742. Hume sought to establish that the balance of power had been a common-sensical idea, reconstructing a historical tradition from the ancient Greeks up until his own time. Even if not expressed, the principle, he held, “is founded so much on common sense and obvious reasoning, that it is impossible it could altogether have escaped antiquity”; it had “naturally discovered itself in foreign politics” (Hume [1742] 1987: 337, 334). Being the first to draw the line so far back in time, he constructed an age-old tradition of the balance of power against those seeking to question its existence. Indeed, the balance of power had been occasionally mentioned throughout the fifteenth, sixteenth, and seventeenth centuries as a metaphor to describe a political situation. For instance, Machiavelli's friend Francesco Guicciardini, in his Storia d'Italia (“History of Italy”), described Italy as being in a “state of balance” between the different city-states.

Even if authors from Guicciardini onwards sporadically mentioned a “balance,” it is the eighteenth century that is considered the “golden age” of the balance of power. Even if frequently used also in the late 1600s, many authors of international politics and history consider the Treaty of Utrecht of 1713 the inauguration of this golden age.

The Treaty of Utrecht established peace after the War of the Spanish Succession, and included the balance of power as a core principle in the treaty text. The reason was a fear that either Spain or France would become too powerful – a tyranny that would dominate Europe and all of its states. For instance, in 1705, fearing that France would take over Spain, the British queen, Anne, said that “if the French King continues Master of the Spanish Monarchy, the Balance of Power in Europe is utterly destroyed,” and he would be able to become a despotic ruler of the whole world (Parliament 1767–1830: 6–9). That is why the balance of power was included as a core principle of the European conduct of states after Utrecht.

And it is precisely Britain that has used the balance-of-power concept the most in its diplomacy for the past 300 years. The English translation of Francesco Guicciardini's History of Italy from 1579 was dedicated to Elizabeth I, styled as the holder of the balance amongst Christian monarchs. The idea in Britain was that the country played the role of a “balancer” in the system of European states. To establish a balance, one should aid the weak, and Britain conceived of itself as the country that could tip the scales in any one direction, as they saw fit. The role of the balancer, many argued, gave Britain an unprecedented power – not only as a Great Power in Europe, but also as the decisive weight in the scale. It was Britain's duty to make certain that no one could become a “universal monarch,” ruling the entire Continent, by aiding the weak part as the power constellations on the Continent changed. Britain protected Europe, and thereby protected itself, by means of the balance of power. Whether this was indeed what Britain did in practice is up for debate, but it remains a fact that many of the political leaders and diplomats who played central roles in developing and using the balance-of-power concept came from Britain.

However, the balance of power was also very much a European concept. Many considered Europe as a kind of federation. What European states were said to have in common was politeness, manners, science, liberty, and protection against arbitrary rule. The balance of power was overall considered an “associational” one; relying on a shared idea of a European community. For example, in 1763 it was argued that “those who have ever heard of the balance of power will consider the states of Europe … as forming one great republic, which interests itself in the concerns of every individual state” (Noorthouck 1773: 403). Even so, wars would sometimes be necessary in order to maintain or adjust a stable balance of power, as in the case of Napoleon in the nineteenth century who threatened the European community with despotic French rule. The goal of a peaceful and stable balance justified the means. That the balance of power meant occasional Great Power wars was the basis for why the United States would oppose the balance of power and the “old diplomacy” in the twentieth century.

Later in the century, one of the most vocal critics of the balance of power was the German scholar Gottlob von Justi. The balance of power had nothing to do with the nature of the European powers, Justi declared; no power has ever acted on the balance-of-power principle, “but […] they have only used this theoretical system to gain allies, and to hide their particular interest and their passions that lead them to war.” Wars have been fought because of the “particular interest of the state or the passion of the rulers.” The balance of power has been driven by envy and fear, Justi argued, not by altruism or a concern for the common interest of Europe. It has been a cause of war, not the remedy. The balance of power has camouflaged self-interests and the “real motives” of states and diplomats (Justi 1758: 116).

With the discipline of international law, the balance of power became a central principle for diplomacy, and could legitimize interventions to preserve the balance of power and thereby the common interest of Europe. Whilst these authors and lawyers argued that intervening in other countries could be justified by the balance of power, others argued that the balance of power demanded the complete independence and inviolability of states, particularly during the nineteenth century.

The independence of nations was a crucial element of the diplomacy surrounding the Concert of Europe, taken to be a particularly peaceful period of European history. Here, the balance of power was increasingly considered a means to help states protect their independence. The balance of power relied on the integrity of its parts. Later, in the twentieth century, the US diplomat and secretary of state Henry Kissinger would look to the diplomats of the Congress of Vienna, like Friedrich von Gentz, Lord Castlereagh, and Prince Metternich, in forming his view of the importance of a stable balance of power in world politics. However, during the Congress of Vienna, the concept of an “equilibrium” of social forces, and not the balance of power, was the predominant one. Social forces threatening the stability of the European system were considered more urgent than the relations between states within the system (Andersen 2016).

For Cobden, the balance of power was so inconsistent that it was nothing more than a myth.

But the tendencies of associating the balance of power with independent nation-states continued as nationalism grew in Europe. The outbreak of the Crimean War in 1853 may be considered the end of the Concert system in Europe and a result of privileging national interests in calculations of the balance of power. Further, many considered the balance-of-power idea to be partially responsible for the outbreak of the First World War, justifying wars and nation-states clashing. The balance of power had become less about managing a European community, and more about raw power politics between isolated nation-states. The same arguments as Justi's in the 1700s and Cobden's in the 1800s were also presented as a case against the balance of power in the United States preceding the First World War, a war which inaugurated a new decade of criticism against the balance of power.

The balance of power was increasingly associated with a past world of deceitful and secret old diplomacy. Liberals considered the lack of transparency as a leading cause of the war – decisions were taken behind closed doors, and there was no accountability for the diplomats and politicians only following their own interests. The balance of power was one expression of this, it was argued in the United States – a state founded on the principle that it would be different from the old Europe and their Great-Power wars and therefore different from the operation of the balance of power.

The British scholar G. Lowes Dickinson's widely read 1916 book The European Anarchy came to define much of the subsequent discussion about the role of the balance of power in the “new world” that was at hand after the First World War. Dickinson's book implied that individuals such as the German kaiser and the Russian tsar were not to carry all blame for the war: there was something about the system of international relations that had gone awry. Dickinson maintained that this system of “anarchy” and the traditional practices of European diplomacy had led to the Great War, and the new Great Power, the United States, would now have to ensure a transition from anarchy and the balance of power to a lawful international order.

The argument resonated well in the USA, where the balance of power was traditionally an object for many to despise. After US president James Monroe had proclaimed his “Monroe Doctrine” in 1823, which claimed the American continent as the exclusive domain of US foreign policy and urging US withdrawal from European affairs, the country had defined its moral purpose in opposition to the balance of power. The nineteenth-century liberal Richard Cobden had considered the United States an ideal in this respect: “America, with infinite wisdom, refuses to be a party to the ‘balance of power’” (Cobden [1836] 1867: 280).

The balance of power had no place in Wilson's “new diplomacy,” as it was considered to have had a part in bringing about the war. Rather, what was now needed, Wilson argued, were “open covenants of peace, openly arrived at.”

However, the Second World War shattered the hopes for a new and peaceful world. After the Second World War, as the Cold War set on, the concept of the balance of power became more widely accepted, also in the United States. In 1947 DeWitt Clinton Poole, a centrally placed US diplomat and presidential envoy, even argued that the balance of power was an American idea. Furthermore, a complex balance of power was for Poole a requirement for a working United Nations (UN). The new invention, the atomic bomb, had not changed this, he maintained. A balance of power was needed also in the nuclear age. Some agreed – even more disagreed.

Shortly after the first test of a nuclear weapon, the military strategist Bernard Brodie had published The Absolute Weapon. He argued that it was not the use itself, but the threat of use of this new weapon, that could lead to peace and stability. This seemed to promise a revision of the workings of the international system. In the 1950s, therefore, some started arguing that the balance of power was irrelevant because of nuclear weapons technology. Civilian scientists increasingly challenged the authority of the military establishment, arguing that the military's traditional ways of understanding war and conflict, such as a balance of power, were irrelevant for the nuclear wars of the future.

Whereas some held that the balance had become irrelevant because of nuclear weapons, others defended the old lessons from European diplomacy, and the concept of the balance of power. Herbert Butterfield, an early founder of the “English School” of international relations, defended the balance of power also in a nuclear age. So did Robert Ingrim, arguing that the balance of power was still relevant, and that the concept could not be blamed for the world wars. The United States is not the holder of the balance, but a defender of it. Glenn H. Snyder claimed that the “balance of terror” was merely a sub-category of the most general theory of equilibrium, the balance of power. The presence of nuclear arsenals would only modify the balance. An early realist IR scholar, Hans Morgenthau, argued that nuclear policy was not a foreign policy tool, but a means of ensuring that the national interest can be supported by traditional means. Nuclear policy is a background condition that must be managed through cooperation, where peace and stability are the ultimate goal. Thus, the balance of power is not obsolete, he maintained: it operates, day to day, in the shadow of nuclear policy – which is a different matter entirely.

After the Second World War, therefore, many debated whether, in some unprecedented way, there was no balance, order, or structure to international politics at all. Did Cold War diplomacy operate in a completely new and unprecedented world? The initial concerns of many IR scholars went parallel to these discussions: Who would be the new guarantor of world order, and how? Was there a balance of power? Who could secure a new one? The new discipline of international relations aimed to contribute to resolving these questions by reintroducing the balance-of-power concept as central to the practice of diplomacy.

The Balance of Power in IR

The Cold War is the period where the balance-of-power principle, as developed by generations of diplomats in Europe, was introduced to the United States in the context of a search for a comprehensive theory of international politics. US academics took the practices of European diplomats as their cue to develop the theory we now know as Realism in IR – the practice of diplomats should be the ultimate reality test for any theory. Traditional diplomatic practices had to be systematized and made readily available for some sort of theoretical and scientific generalization, and the balance-of-power principle was seen as ideal for that purpose. Here, two realist writers stand out: Hans Morgenhau and Kenneth Waltz.

Morgenthau claimed that just as human beings, states follow a drive for power and domination. This behavior can be mitigated by the balance of power, ensuring some degree of stability and order, even in an environment of self-seeking egoistic states. Morgenthau argued that the balance of power and the policies aimed at establishing and maintaining it were crucial for the stability of international politics. He also argued, however, that the balance of power would be a result of a struggle for power where every state must aim for superiority and not explicitly for a balance of power. Yet, superiority is exactly what one should not aim for, according to the many diplomats who had been using the concept in former times. Aiming for superiority is dangerous, as it will trigger wars and counter-balancing. This is one of various ambiguities in Morgenthau's work, who operates with many different and at times contradictory definitions and implications of the balance of power.

Kenneth Waltz therefore aimed to establish the balance of power as a theory on a more consistent and scientific level. Waltz, in his Theory of International Politics, maintains that the balance of power is the closest we come to a “distinctively political theory of international politics” (1979: 117). The balance of power is the theory of realist international politics. Because of the structure of international politics – where every state fends for itself in an international anarchy – the way to protect oneself as a small state is to engage in balancing against a threatening great power. Today's international politics with the United States as a sole superpower is not normal, he would argue, as all countries historically have worked to right the balance when one actor threatens to become too big.

Instead of focusing on each and every component of a system – such as all the various states with all their different characteristics and foreign policies – Waltz wanted to make a simpler theory by focusing on what all have in common, namely the structure within which they are acting. The assumption is that all states are alike in the way they function as a part of the system, as every state has one overriding wish: to survive. They differ only in their capabilities: some states are powerful and big, others have fewer capabilities. Still, as all states learn from the successful states in the system, a balance of power will eventually emerge. Waltz's balance-of-power theory is therefore all about how an anarchical system characterized by self-help imposes constraints on states. Contrary to former theorists, it is not the skillful diplomatic maneuvering or political traditions that decide the balance of power but the recurring patterns of politics he calls the international structure. The balance of power will emerge whether politicians and diplomats intend it or not.

In 1757, Antoine Pequet had argued that balance is not a physical equality of strength, but the “balance can be estimated exactly only by the more or less judicious and intelligent use” states make of their “forces” (1757: 191–206). The balance of power is therefore shifting constantly, because “a Power better governed than others” can “shift the real balance and that of opinion in its favour.” Already then, in the mid-1700s, we see one of the precursors to another of Waltz's arguments; that there is a difference between internal and external balancing.

Waltz argued that balancing can be done through external or internal means. Internal balancing means channeling a state's resources to armaments, extracting resources, organizing the state properly, preventing revolts and infiltrations, and so on, to protect and strengthen oneself to be able to compete more effectively. States do external balancing through making alliances with others to halt a rising power. Even if cooperation is difficult between states, when facing a common or existential threat, states may temporarily put aside their disputes and band together against the dominant state.

These accounts have a strong hold on the discipline of IR, but today authors are also challenging these classical theories of the balance of power. John Mearsheimer, a proponent of “offensive realism,” takes Waltz's arguments a step further. Whilst Waltz implies that a state can be safe enough only having to defend itself, Mearsheimer argues that maintaining the status quo is never a successful strategy – there is no time to rest, states have to be on the offensive and work constantly to maximize their power, because that is what everyone else is doing. No cooperation is possible; the structure of the international system compels states to engage in unrelenting competition to tip the balance in one's favor. The possibility of defecting from balance-of-power coalitions is therefore always present. Consequently, he argues that all states at all times are relentlessly engaging in internal balancing. States must spend all their resources on maximizing power to avoid falling behind in the international competition; there is no time to be complacent.

These are all realist scholars. A different perspective on the balance of power comes from authors pertaining to the English School, who argue that the balance of power is an institution of international society, binding states tighter together. Hedley Bull argued that one function of the balance of power has been to foster an international society resting on shared understandings between states. It is not only a factor in an international system. The English School emphasizes the earlier historical theorists' emphasis on the balance as part of a European community and social order, rather than an exclusive focus on raw power-politics and national competition. Many authors of this school, such as Richard Little, adopt a historical perspective on the balance of power, whilst also arguing that it is analytically useful to explain international stability and community.

Whilst not a member of the English School, Stephen Walt also adds a social aspect to the balance of power, arguing that not only material capabilities count. Perceptions also matter. He uses the concept “balance of threats” in arguing that what states perceive as a threat matters a great deal in addition to material capabilities and geography. States, that is, will ally against what is seen to be the most threatening state. They balance against perceived threats, not against any objective measure of power seen in isolation. For instance, a rising state could be considered friendly and similar to oneself, and therefore not be seen as an impending threat.

The implication is that another option is to join a rising power, rather than to balance against it. Technically, this is called “bandwagoning.” Waltz argued that states would join the weaker side, because it is the stronger side that threatens them. Bandwagoning, Waltz argued, is too risky because it allows the enemy to grow stronger. Therefore, bandwagoning will only happen as a last resort. Randall L. Schweller, however, points out that there are also revisionist states in the system that will work to overthrow the existing order – the status quo. Bandwagoning may therefore become more prominent. When large states successfully challenge the existing international order, small states may ally with the dominant, rising power to assure their own survival. They will not primarily try the risky strategy of balancing against a state that can do whatever it wants anyway.

Yet another alternative response to rising powers might be so-called “soft balancing.” The capabilities of the dominant state may be so overwhelming that traditional balancing is futile or too risky. Then, some have argued, an alternative is soft balancing. Hard balancing would be the classical mode of balancing between rivalrous states, to balance internally by building up their capabilities and externally by forming alliances and counter-alliances. Soft balancing, on the other hand, is a more indirect way of balancing, whereby states use resources short of military buildups to establish understandings with other, often likeminded states, to undermine the stronger one. The point is to increase the costs of the unilateral policies of the stronger state by undermining it through economic, diplomatic, institutional, or even cultural means. Collaboration in international institutions could be one example.

However, how do we separate balancing behavior from other “soft” diplomatic strategies that are not necessarily including the balancing component? Further, is there a difference between “a balance of power” and “balancing”? Normally, balancing is viewed as something states do, whilst balances of power are viewed as the outcome on the level of the system. In continuation of this, Dan Nexon (2009) has argued that it is important to separate between balance-of-power theory, theories of power balances, and theories of balancing. Balancing and the balance of power is a broader phenomenon than what realist IR theory traditionally implies. We should not abandon balance-of-power theory, but expand it by rethinking realist assumptions, incorporating other theoretical traditions, and investigating more thoroughly how the balance of power is used in practical politics. This is important also given that some historical studies find scant evidence of traditional balances of power in operation. Historians like Paul W. Schroeder (1989) have questioned the presence of a static concept of a balance of power, mustering historical evidence to the contrary. Whilst there is less evidence supporting traditional balance-of-power theory, Nexon argues, a focus on balancing behavior could be more effective to explain international politics, as well as being a move to disconnect balancing from realist theories of international relations, opening up a wider field of research on states' power-political behavior.

The Balance of Power Today

In sum, the balance of power has been used throughout history, both in practice and theory, and is still with us. Today, the most debated theoretical question is, why have no states successfully balanced against the United States? Why is the world order in a state of unbalance? Is this unprecedented in the history of world politics, or does it reflect a fault in our balance-of-power theories? Many of the debates mentioned above, and the suggested readings below, refer to this problem in different ways.

Whilst the balance of power is still on the agenda for scholarship, also in the world of practical politics we still see the occasional mention of a balance of power. In 2002, one year after the 9/11 terrorist attacks, President Bush's assistant for national security affairs, Condoleezza Rice, delivered a lecture entitled “A Balance of Power that Favors Freedom” (Rice 2002). President Bush's National Security strategy, she explained, “calls on America to use our position of unparalleled strength and influence to create a balance of power that favors freedom” against “tyrants” and “terrorists.” The Obama administration argued for an “East Asia–Pacific Rebalance,” “positioning the United States to better promote its interests as the center of global politics” (US Department of State 2013). China has invoked the supposed “ancient roots” of the balance-of-power concept, arguing that the United States and China, “the incumbent superpower and the biggest rising developing nation,” “face the dilemma of falling into the ‘Thucydides Trap’” – referring to the Melian Dialogue, where Thucydides stated that “the strong do what they can and the weak suffer what they must” – taken to be an expression of the idea that changes in the balance of power leads to war. In the context of increasing Russian assertiveness in the 2010s, we can also find frequent references in the media to the balance of power in the Mediterranean, the Middle East, and globally. The balance of power is and has been important and useful, both as theory and as politics, a concept to use to formulate policy positions, and a concept from which to distance oneself.

The jury is still out on whether it is a useful theoretical concept for us as scholars. In any case, it has definitely been useful for diplomats throughout history, and a central concept of diplomatic practice in Europe and beyond. This also means that it is difficult to find any clear definition of what the balance of power really is – a variety of political actors and scholars have been and are using the concept for very different purposes, and often with contradictory meanings. Therefore, in the study of diplomacy, it can be of analytical value if used with care, but it is also definitively worth investigating as being an integral component of the historical practice of diplomacy up until the present day (see Andersen 2016).

SEE ALSO: Cold War Diplomacy; Concert of Europe; Congress of Vienna (1815); International Law and Diplomacy; International Relations Theory and Diplomacy; Machiavelli, Niccolò (1469–1527); Medici, Lorenzo de' (1449–92); Morgenthau, Hans J. (1904–80); New Diplomacy; Oil Diplomacy; Peloponnesian War (431–404 bce); Thucydides; Treaty of Utrecht (1713); Vattel, Emerich de (1714–67); Venetian Diplomacy; Waltz, Kenneth (1924–2013); Wilson, Woodrow (1856–1924)