International Relations

The Ideal Structural Explanation of International Politics

Per Magnus Muren (2016), The London School of Economics and Political Science, Msc in International Relations 


John Mearsheimer argues in The Tragedy of Great Power Politics that: “Structural factors such as anarchy and the distribution of power are what matter most for explaining international politics.”[1] This essay, however, will argue that Mearsheimer’s structural realism or offensive realism offers little explanatory or predictive value in the complex world of international politics and should rather be viewed as an ideal type of international politics or as a model for policy prescription.

Mearsheimer introduces the concept of offensive realism as a supplementary theory to the already well established neo-realism or structural realism of Kenneth Waltz that maintains that anarchy and the distribution of capabilities are the most fundamental variables in explaining the international system.[2] Both agree that states seek survival in the self-help world of international anarchy, but differ in their understanding of how to best guarantee survival. Where Waltz emphasises the balance-of-power and a defensive attitude towards other great or rising powers[3] as well as the difference between multipolar and bipolar systems in maintaining the balance-of-power,[4] Mearsheimer, on the other hand, argues that states actively pursue as much power as possible. He claims that “the international system creates powerful incentives for states to look for opportunities to gain power at the expense of their rivals… A state’s ultimate goal is to be the hegemon in the system.[5] This approach suggests that power, in the form of military capability, is the only security guarantee a state can obtain in the system and they should therefore seek to gain as much as possible. In short: “The best defence is a good offence.”[6]

In his world of power maximizing states Mearsheimer argues that a few structural factors are the most important in explaining international politics, independently of ideology, domestic politics, identity and individual leadership. He bases his explanatory theory on five “bedrock assumptions.” Firstly, the international system is anarchic and sovereignty belongs to states as no higher ruling body exists. Secondly, all great powers possess some offensive military capability, which enables them to hurt or destroy each other. Thirdly, the system is fundamentally uncertain as one can never be sure of the intentions of other states. And in this uncertainty it is also assumed that states seek survival as their primary goal and, lastly, they do so as rational actors.[7]

The claim of structural realists and Mearsheimer is that these factors can generally explain international politics. They justifiably focus on the great powers, defined as those states capable of putting up a serious fight against the most powerful state in the world, as these states have the greatest impact on what happens in the system,[8] and suggest that great powers will always be locked in a struggle for power as long as the international system remains anarchical.[9] Based on the structural factors of anarchy, military capability and uncertainty the theory should be able to predict international outcomes and the behaviour of great powers. By omitting other factors like ideology, leadership and domestic politics Mearsheimer acknowledges that offensive realism does not answer every question and that the omitted factors sometimes dominate a state’s decision making process. He points out that offensive realism would have expected Germany to go to war against France in 1905 rather than 1914 as Russian balance was temporarily weakened by Japan, and Germany’s relative power was greater.[10] However, one might very well argue that it is the anomalies that are significant when evaluating a theory. Mearsheimer nonetheless maintains that his theory, for the most part, is an “excellent tool for navigating through the darkness” of international politics.[11] And he insists on preserving the parsimonious nature of realist theory although that might leave out important information.[12] The theory, according to Mearsheimer, is both descriptive, in that it explains the past and predicts the future with few anomalies, as well as prescriptive, explaining how states best survive in a dangerous world. Although the descriptive element is presented as the most important aspect of his theory.[13]

Superficially copying the natural sciences and Newtonian physics the focus for structural realists is more on the descriptive rather than the prescriptive aspect of theory as well as presenting the world in an ordered and parsimonious way. But this is a fundamental misunderstanding of how the natural sciences work. In physics we have Einstein’s fairly parsimonious theory of general relativity that explains gravity and space-time using a rather short and sweet equation, but we also have the standard model of particle physics, which explains the weak and strong nuclear forces, electromagnetic force and fundamental particles using a tapestry of equations in its attempt to incorporate all of the known empirical data. Parsimony is good for clarity but does not come at the expense of reality. If there are anomalies to the theories of physics the theory must be changed to incorporate the new evidence or a completely new theory is required. Given the acknowledged limitations and anomalies of offensive realism the theory should limit itself to a prescriptive role, which is largely what we have seen in Mearsheimer’s career.

Throughout the book Mearsheimer warns of the impending conflict between the United States and China as they inevitably fight over regional control in Northeast Asia[14] and he continuously advocates for a containment policy by the United States towards China, reminiscent of the containment policy towards the Soviet Union and Communism.[15] He has also been very critical of the Vietnam War, arguing that it hurt America’s strategic position.[16] And he was strongly against the war in Iraq, labelling it an unnecessary war and suggesting that the Bush administration did not rationally evaluate the real threat Saddam posed to U.S. interests.[17] The idea that states rationally act in accordance with Mearsheimer’s theory has been severely undermined by the behaviour of the United States the last 45 years. If it was true that the great powers generally sought regional hegemony and the preservation of their power in a rational fashion, with only a few exceptions in extreme circumstances, it would be no need for Mearsheimer to prescribe realist policies to American leaders. But this has clearly not been the case. One of the best examples of Mearsheimer undermining his own structural theory is his piece with Stephen Walt arguing that the pro-Israel lobby exert such an influence on U.S. domestic politics that they have shifted U.S. foreign policy in the Middle East away from American interests in favour of a special relationship with Israel. Not merely a blip on the radar or statistical anomaly, they argue that domestic politics have governed American policy in the Middle East at least since 1967,[18] and not interests defined by the distribution of capabilities in an anarchical system as expected by his theory.

Neorealist theory and Mearsheimer in particular believe, and rightly so, that the ultimate test of a theory is how well it explains the real world.[19] But the end result is a misunderstood simplification of reality that does not match the empirical data. The theory is preserved in favour of reality while in the natural sciences the theory is altered to incorporate the empirical world. If Mearsheimer’s theory was generally right, world history would be a lot less interesting than it actually is. If states generally acted rationally to preserve or increase their power and for the most part fought prudent wars with clearly defined strategic goals, we would see few empires crumble under their own weight and few rash decisions or charismatic leaders defining the course of history. He mentions Germany in 1905 as an anomaly to his theory but suggests that the leadership and ideology of Germany was irrelevant in 1914, the only thing that mattered was relative power.[20] But let us apply that logic to 1939 instead. Germany under different leadership than Hitler and the Nazis would perhaps have attempted to gain European hegemony, but there is no reason to think that a different set of ideologies merely focused on interests would have gone through the trouble of exterminating millions of Jews. This is a rather significant world event that cannot be explained by a rational pursuit of regional hegemony, and world history is full of these significant events that give substance and meaning to the wars we fight in the international system. The structural explanation of international politics is more of an ideal version of reality. It would be nice if the world was that simple and we could measure all the significant variables in international relations, but reality is much more complex than that and arguably the things that are left out of structural explanations are the most important ones.

One of the other significant contributions of The Tragedy of Great Power Politics is the introduction of geography as a real and significant factor in determining the material capabilities and strategic situation of great powers. Geography has of course been a common factor in strategic literature for a long time but absent in Waltz’ neorealism and other IR discussions on capabilities and the balance-of-power. Mearsheimer argues that land based power is superior to air and sea power as it is capable of holding together and protecting territory. He also focuses on the stopping power of water as a major reason why a global hegemon would be impossible, and regional hegemony is therefore the highest goal states can strive for.[21] In his logic of anarchy great powers would pursue world hegemony were it not for the major oceans separating them. Campbell Craig, however, has argued that the thermonuclear revolution lead Cold War realists, including Morgenthau and Niebuhr to implicitly argue in favor of a world state emerging because the stopping power of water disappeared with the emergence of nuclear weapons and ICBMs.[22] Historically we also have evidence of two of the most powerful states of all time, imperial Britain and the U.S. today, being naval and air powers respectively. We can also expect that the stopping power of water will diminish more and more for every new communications technology, transportation device and ranged weapon invented. P.W. Singer and others predict that future wars will likely take place both in outer-space and cyber space,[23] where the stopping power of water counts for little. Much of Mearsheimer’s argument favouring regional hegemons rely on the stopping power of water, but that might not be an adequate reason why states do or do not strive for regional or global hegemony.

Mearsheimer’s offensive realism seems simplified for the sake of simplicity to the point where it no longer accurately captures reality. His career arguing against U.S. foreign policy clearly demonstrates E. H. Carr’s adage that it is impossible to be a consistent and thorough-going realist.[24] When the theory does not live up to reality the predictive value of the theory essentially becomes that: If states act according to our predefined rationality we can understand them. But it is of course quite easy to say that you can predict what will happen in international politics if states simply do what you tell them. And it is precisely in this way Mearsheimer’s idealistic simplification of international politics takes on a more prescriptive nature. He obviously wants to preserve the position of the United States in the international system and argues that fighting prudent wars and containing China is the rational thing to do. It might very well be true that gaining relative power increases your survival chances, but there is no obvious reason why that is the only way to survive, or even the best one, nor any empirical certainty that states will actually behave according to offensive realism’s rationality. It is of course commendable that Mearsheimer takes an interest in foreign policy and tests his theory to an extent that Waltz did not. It just so happens that the result is a prescriptive rather than an explanatory theory. An explanatory theory that seeks to describe and predict the real world needs to take account of the complexities of that world. Parsimony is not a virtue in itself if it cannot explain how states or human beings behave empirically.


Carr, E. H. The Twenty Years’ Crisis, 1919-1939: An Introduction to the Study of International Relations. ed. Michael Cox. Palgrave, 2001.

Craig, Campbell. Glimmer of a new Leviathan. New York: Columbia University Press, 2003.

Mearsheimer, John J. China’s Unpeaceful Rise. Current History, 105:690, Apr 2006. p160.

Mearsheimer John J. McNamara’s War. Bulletin of the Atomic Scientists, 49:6, Aug 1993.

Mearsheimer John J. The tragedy of great power politics. London: W.W. Norton, 2001.

Mearsheimer John J. and Walt, Stephen M. An Unnecessary War. Foreign Policy, Jan/Feb 2003. p50-59.

Mearsheimer John J. and Walt, Stephen M. The Israel Lobby and U.S. Foreign Policy. Middle East Policy, 13:3, 2006. p29-87.

Singer, P.W. and Cole, August. Ghost Fleet: A Novel of the Next World War. New York: HMHCO, 2009.

Waltz, Kenneth. Theory of International Politics. USA: Waveland Press, 2010.

[1] Mearsheimer. The Tragedy of Great Power Politics. (2001), p12.

[2] Waltz. Theory of International Politics. (1979), p88.

[3] Ibid, Chapter 6.

[4] Ibid, Chapter 8.

[5] Mearsheimer (2001), p24.

[6] Ibid, p41.

[7] Ibid, Chapter 2.

[8] Ibid, p5-6.

[9] Ibid, Introduction.

[10] Ibid, p12.

[11] Ibid, p13.

[12] Ibid, p107.

[13] Ibid, p13.

[14] Ibid, p4.

[15] Mearsheimer. China’s Unpeaceful Rise. (2006).

[16] Mearsheimer. McNamara’s War. (1993).

[17] Mearsheimer and Walt. An Unnecessary War. (2003).

[18] Mearsheimer and Walt. The Israel Lobby and U.S. Foreign Policy. (2006).

[19] Mearsheimer (2001), p6.

[20] Ibid, p12.

[21] Mearsheimer (2001), Chapter 4.

[22] Craig. New Leviathan. pXVII.

[23] Singer and Cole. Ghost Fleet. (2009).

[24] Carr. The Twenty Year’s Crisis. (2001) p84.

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