Offensive realism is a structural theory belonging to the realist school of thought first postulated by John Mearsheimer that holds the anarchic nature of the international system responsible for aggressive state behaviour in international politics. It fundamentally differs from defensive realism by depicting great powers as power-maximising revisionists privileging buck-passing over balancing strategies in their ultimate aim to dominate the international system. The theory brings important contributions for the study and understanding of international relations but remains nonetheless the subject of criticism.
Theoretical Origins 
Offensive realism is a prominent theory of international relations belonging to the realist school of thought, which includes various sub-trends characterised by the different perspectives of representative scholars such as Robert Gilpin, Randall Schweller, Eric J. Labs and Fareed Zakaria. Yet, to date, the most important variant of offensive realism is that of John J. Mearsheimer as fully developed in his book The Tragedy of Great Power Politics. While Mearsheimer’s offensive realism theory does reiterate and build on certain assumptions elaborated by classical realists, it departs completely from this branch by using positivism as a philosophy of science and by adding a system-centric approach to the study of state behaviour in international politics based on the structure of the international system. Accordingly, his offensive realism pertains to the sub-branch of neorealism alongside other structural theories such as defensive realism.
Main Tenets of Offensive Realism 
- Great powers are the main actors in world politics and the international system is anarchical
- All states possess some offensive military capability
- States can never be certain of the intentions of other states
- States have survival as their primary goal
- States are rational actors, capable of coming up with sound strategies that maximize their prospects for survival
Like defensive realism, offensive realism posits an anarchic international system in which rational great powers uncertain of other states’ intentions and capable of military offensive strive to survive. Although initially developed from similar propositions than defensive realism, Mearsheimer’s offensive realism advances drastically different predictions regarding great power behaviour in international politics. Mainly, it diverges from defensive realism in regards to the accumulation of power a state needs to possess to ensure its security and issuing strategy states pursue to meet this satisfactory level of security. Ultimately, Mearsheimer’s offensive realism draws a much more pessimistic picture of international politics characterised by dangerous inter-state security competition likely leading to conflict and war.
Status Quo Vs. Power-Maximising States 
John Mearsheimer’s offensive realism intends to fix the ‘status quo bias’ of Kenneth Waltz’ defensive realism theory. While both realist variants argue that states are primarily concerned with maximising their security, they disagree over the amount of power required in the process. To the contrary of defensive realism according to which states are status quo powers seeking only to preserve their respective positions in the international system by maintaining the prevailing balance of power, offensive realism claims that states are in fact power-maximising revisionists harbouring aggressive intentions. Indeed, in offensive realism, the international system provides great powers with strong incentives to resort to offensive action in order to increase their security and assure their survival. The international system characterised by anarchy—the absence of a central authority capable of enforcing rules and punishing aggressors—uncertain state intentions and available offensive military capabilities, leads states to constantly fear each other and resort to self-help mechanisms to provide for their survival. In order to alleviate this fear of aggression each holds of the other, states always seek to maximise their own relative power, defined in terms of material capabilities. As Mearsheimer puts it: "they look for opportunities to alter the balance of power by acquiring additional increments of power at the expense of potential rivals" since "the greater the military advantage one state has over other states, the more secure it is." States seek to increase their military strength to the detriment of other states within the system with hegemony—being the only great power in the state system—as their ultimate goal. John Mearsheimer summed up this view as follows: "great powers recognize that the best way to ensure their security is to achieve hegemony now, thus eliminating any possibility of a challenge by another great power. Only a misguided state would pass up an opportunity to be the hegemon in the system because it thought it already had sufficient power to survive." Accordingly, offensive realists such as Mearsheimer believe that a state’s best strategy to increase its relative power to the point of achieving hegemony is to rely on offensive tactics. Provided that it is rational for them to act aggressively, great powers will likely pursue expansionist policies, which will bring them closer to hegemony. While global hegemony is nearly impossible to attain due to the constraints of power projection across oceans and retaliation forces, the best end game status states can hope to reach is that of a regional hegemon dominating its own geographical area. This relentless quest for power inherently generates a state of "constant security competition, with the possibility of war always in the background." Only once regional hegemony attained do great powers become status quo states.
Balancing Vs. Buck-Passing State Behaviour 
The emphasis offensive realism puts on hegemony as states’ end aim stands in sharp contrast to defensive realism’s belief that state survival can be guaranteed at some point well short of hegemony. In a defensive realist mindset, security increments by power accumulation end up experiencing diminishing marginal returns where costs eventually outweigh benefits. Defensive realism posits that under anarchy there is a strong propensity for states to engage in balancing—states shouldering direct responsibility to maintain the existing balance of power—against threatening power-seeking states, which may in turn succeed in "jeopardiz(ing) the very survival of the maximizing state." This argument also applies to state behaviour towards the most powerful state in the international system as defensive realists note that an excessive concentration of power is self-defeating, triggering balancing countermoves. Yet, Mearsheimer challenges these claims by making the argument that it is rather difficult to estimate when states have reached a satisfactory amount of power short of hegemony and costly to rely extensively on balancing as an efficient power-checking method due to collective action issues. According to him, when a great power finds itself in a defensive posture trying to prevent rivals from gaining power at its expense, it can choose to engage in balancing or intervene by favouring buck-passing—transferring the responsibility to act onto other states while remaining on the sidelines. In order to determine the circumstances in which great powers behave according to one or the other, Mearsheimer builds on Waltz’ defensive realism by including a second variable—geography—alongside the distribution of power. On one hand, the choice between balancing and buck-passing depends on whether the anarchic international system is of a bipolar, balanced or unbalanced multipolar architecture. On another hand, state geographic location in terms of border sharing and stopping power of water also influences great powers’ strategy preference. Combined together, these two variables allow him to establish that great powers tend to favour—to the contrary of defensive realism predictions—buck-passing over balancing in all instances of multipolarity except for those that include a potential hegemon. Responding to defensive realists’ posture on state behaviour towards the most powerful state in the international system, Mearseimer believes that threatened states will reluctantly engage in balancing against potential hegemons but that balancing coalitions are unlikely to form against a great power that has achieved regional hegemony. This lack of balancing is best explained by the regional hegemon’s newly acquired status quo stance, which follows from the geographical constraints on its power projection capability. Instead of relying on offensive actions, a regional hegemon finds itself in a defensive position seeking to avert threats to its hegemonic status by preventing the rise of any peer competitors in other areas. As such it will behave as an offshore balancer, passing the buck to local neighbours of the potential hegemon and engaging in balancing only as a last resort.
Contributions and Criticism 
Mearsheimer’s offensive realism represents an important contribution to international relations theory yet also generated important criticism. While the inputs and critics below provide a good sample of the theory’s contributions and the kind of arguments that have been addressed against it, the listing should in no case be considered as exhaustive.
Theoretical Inputs 
Firstly, scholars believe that Mearsheimer’s offensive realism provides a nice complement to Waltz’ defensive realism. The theory adds to defensive realists’ argument that the structure of the international system constrains state behaviour. Setting to rectify the status quo bias pertaining to defensive realism by arguing that anarchy can also generate incentives for states to maximise their share of power, offensive realism solves anomalies that Waltz’ theory fails to explain. Mainly, the theory is able to provide an explanation for the amount of conflict occurring among states in the international system. As Snyder states, Mearsheimer’s offensive realism "enlarges the scope of neorealist theory by providing a theoretical rationale for the behavior of revisionist states." Moreover, this complementarity could signify theoretical interrelation with the two theories working in alternation to explain state behaviour, thereby allowing for a "more complete structural realist theory that can more accurately account for both defensive and offensive state behaviour." Secondly, these scholars uphold the argument that Mearsheimer’s offensive realism significantly contributes to foreign policy theory and alliance theory. More specifically, Mearsheimer’s theory goes a step further than structural defensive realism by successfully theorising both international politics and foreign policy. Contrary to Waltz’ rejection of defensive realism as a theory capable of explaining foreign policy on top of international politics, offensive realism includes explanations of both international outcomes pertaining to the systemic level of analysis and individual state behaviour. Additionally, the inclusion of new variables such as geography alongside the distribution of power enhances offensive realism’s potential to make specific assumptions about states’ pursue of aggressive actions and resort to balancing and buck-passing strategies.
Theoretical Flaws 
To begin with, scholars have pointed out several logical issues within Mearsheimer’s offensive realism. Snyder rejects Mearsheimer’s view of the security dilemma as "a synoptic statement of offensive realism." He argues that offensive realism’s positing of all states as revisionists removes the central proposition—uncertainty about other states’ intentions—on which the whole concept of security dilemma is grounded. Aggressive great powers’ measures to maximise their security threaten others which leads to an actual justified security competition between states rather than an unnecessary one based on hypothetical threats. Toft indicates flaws relating to offensive realism’s level of analysis. According to him, the inclusion of the non-structural geography variable to explain great power behaviour shifts the theory’s focal point of analysis from system-wide dynamics to regional ones. Considering the theory’s regional security analyses, he further argues that offensive realism fails to clearly define what constitutes a region with "entities like Europe or North-East Asia (taken) for granted", leaving room for scholarly disapproval. Christopher Layne further highlights problems associated with the geography variable. He criticises Mearsheimer’s reasoning according to which the "stopping power of water" prevents a great power from achieving global hegemony as this constraint doesn’t seem to apply to the case of an emerging rival’s capacity to exercise influence beyond its own neighbourhood. As he states, "apparently water stops the United States from imposing its powers on others in distant regions, but it does not stop them from threatening American primacy in the Western Hemisphere." Moreover, he finds offensive realism’s classification of regional hegemons as status quo powers difficult to reconcile with the theory’s emphasis on great powers as relentless power-maximisers. In this sense, Layne questions the ability of the water constraint to transform a power-maximising state into a status quo power and contradicts Mearsheimer by arguing that a regional hegemon remains subjected to the quest for security, thereby striving to attain global hegemony.
A second group of criticism addresses the issue of offensive realism’s restrictive focuses. Scholars have criticised Mearsheimer’s theory for failing to take into account domestic politics. No attention is paid to a rising power’s internal political functioning, its economy or society, which play a role in a state’s decision-making process, in turn influencing its behaviour in international politics. Moreover, Snyder argues that no consideration is given to transnational threats such as terrorism, and that Mearsheimer’s emphasis on security makes him ignore states’ non-security interests such as ideology, national unification and human rights as an essential aspect of international politics alongside power competition. Additionally, Toft points out that Mearsheimer’s concentration on military capabilities and issuing state capacity for territorial conquest "implies a risk that his analyses miss a host of other ways of gaining and exercising influence." Similarly, political scientists whose primary focus is bargaining models of international conflict note that offensive realism ignores the fact that war is costly. Since those costs in turn make war inefficient, states (even those who do not have hegemony) have incentive to construct bargained settlements. For instance, in a bipolar world with a 70%/30% power breakdown, states would prefer a corresponding 70%/30% breakdown in resources rather than having some of those resources destroyed over the course of fighting. Due to this inefficiency--war's inefficiency puzzle—the constant fighting Mearsheimer proposes would actually make states less secure because the repeated costs of fighting eventually deplete all of that state's power.
Most importantly, scholars have questioned the theory’s empirical validity and prediction ability, which in turn can negatively affect the validity of offensive realism’s prescriptions for state behaviour in international politics. In addition to mentioning the theory’s failure to account for Japan’s 20th century territorial acquisitions, NATO’s continuation or Germany’s non-achievement of regional hegemony in the post-Cold war era, they have also expressed serious doubts regarding offensive realism views on China’s rising power and U.S. regional hegemony. According to them, there is no reason to believe that China as a rational power wanting to ensure its survival will seek hegemony rather than rely on cooperative mechanisms. They similarly contradict Mearsheimer’s arguments regarding the United States. Firstly, weak opposition or balancing inefficiencies rather than geographical constraints are taken as explanations for the uniqueness of the United States’ regional hegemonic position. Toft and Layne go a step further by asserting that Mearsheimer misjudges the U.S. as a regional hegemon engaged in offshore balancing. Instead of being a regional hegemon with the strategic aim of dominating the Western hemisphere while preventing the rise of peer competitors in Europe and Northeast Asia, these scholars believe that empirical data points to the fact that the U.S. has sought and achieved global hegemony, which in turn biases Mearsheimer’s predictions regarding future U.S. strategic behaviour, mainly in terms of its military involvement overseas.
More fundamental criticisms of offensive realism have come from Shiping Tang, "Fear in International Politics: Two Positions," International Studies Review 10 (2008): 451-71; and idem, “Social Evolution of International Politics: From Mearsheimer to Jervis,” European Journal of International Relations 16, 1 (2010): 31-55. Tang's first article argues that Mearsheimer's logic is flawed because his five bedrock assumptions cannot lead to his conclusion. Tang's second article argues that because the international system has always been an evolutionary system, neither offensive realism nor defensive realism has a claim to be a theory for the whole human history: the two realism are theories for different epoches of human history.
- Liu Feng and Zhang Ruizhuan, “The Typologies of Realism”, Chinese Journal of International Politics 1 (2006): 124 and 126.
- Jeffrey W. Taliaferro, “Security Seeking Under Anarchy: Defensive Realism Revisited”, International Security 25:3 (2000/2001): 128-129 and 134.
- Gerald Geunwook Lee, “To Be Long or Not to Be Long–That is the Question: The Contradiction of Time-Horizon in Offensive Realism”, Security Studies 12:2 (2003): 196.
- John J. Mearsheimer, The Tragedy of Great Power Politics (New York, NY: W.W. Norton, 2001).
- Glenn H. Snyder, “Mearsheimer’s World—Ofensive Realism and the Struggle for Security: A Review Essay”, International Security 27:1 (2002): 151.
- Feng and Zheng, Typologies of Realism, 113-114.
- Robert D. Kaplan, “Why John J. Mearsheimer Is Right (About Some Things)”, The Atlantic Magazine (2012) [Available from:http://www.theatlantic.com/magazine/archive/2012/01/why-john-j-mearsheimer-is-right-about-some-things/8839/]
- Kenneth N. Waltz, “Realist Thought and Neorealist Theory”, Journal of International Affairs 44:1 (1990): 34.
- Mearsheimer, J. (2005). Structural Realism, in T. Dunne, M. Kurki & S. Smith, International Relations Theory: Discipline and Diversity. Oxford: Oxford University Press.
- Mearsheimer, John J. "The false promise of international institutions." International Security 19, no. 3 (1994): 5-49.
- Mearsheimer, Tragedy of Great Power Politics, 30-31.
- Eric J. Labs, “Beyond Victory: Offensive Realism and the Expansion of War Aims”, Security Studies 6:4 (1997): 7-8.
- Shiping Tang, “From Offensive to Defensive Realism: A Social Evolutionary Interpretation of China’s Security Strategy”, 148-149, in China's Ascent: Power, Security, and the Future of International Politics, edited by Robert Ross and Zhu Feng. (Ithaca: Cornell University Press, 2008).
- Taliaferro, Security Seeking, 134.
- Mearsheimer, Tragedy of Great Power Politics, 32-33.
- Snyder, Mearsheimer’s World, 153.
- Mearsheimer, Tragedy of Great Power Politics, 20.
- Snyder, Mearsheimer’s World,157-158.
- Kenneth N. Waltz, Theory of International Politics (Reading, MA: Addison-Wesley Publishing Company, 1979): 126.
- Mearsheimer, Tragedy of Great Power Politics, 21.
- ; Sten Rynning and Jens Ringsmose, “Why Are Revisionist States Revisionist? Reviving Classical Realism as an Approach to Understanding International Change”, International Politics 45 (2008): 26.
- John J. Mearsheimer, “China’s Unpeaceful Rise”, Current History 105: 690 (2006): 160.
- Mearsheimer, Tragedy of Great Power Politics, 34.
- John J. Mearsheimer, “The False Promise of International Institutions”, International Security 19:3 (1994-1995): 11-12.
- Mearsheimer, Tragedy of Great Power Politics, 21 and 29.
- Mearsheimer, Tragedy of Great Power Politics, 35.
- Mearsheimer, China’s Unpeaceful Rise, 160.
- Mearsheimer, Tragedy of Great Power Politics, 141.
- Mearsheimer, The False Promise, 12.
- Snyder, Mearsheimer’s World, 154.
- Peter Toft, “John J. Mearsheimer: An Offensive Realist Between Geopolitics and Power”, Journal of International Relations and Development 8 (2005): 390.
- Yuan-Kang Wang, “Offensive Realism and the Rise of China”, Issues & Studies 40:1 (2004): 177.
- Snyder, Mearsheimer’s World, 156.
- Labs, Beyond Victory, 10.
- Mearsheimer, Tragedy of Great Power Politics, 34-35 and 156-157.
- Wang, Offensive Realism, 178.
- Mearsheimer, Tragedy of Great Power Politics, 155, 160, 261 and 272.
- Wang, Offensive Realism, 179.
- Feng & Z Ruizhuan, Typologies of Realism, 124.
- Mearsheimer, Tragedy of Great Power Politics, 271 and 345.
- Keir A. Lieber and Gerard Alexander, “Waiting for Balancing Why the World Is Not Pushing Back”, International Security 30:1 (2005): 111-112.
- Jack S. Levy and William R. Thompson, “Balancing on Land and at Sea: Do States Ally Against the Leading Global Power?” International Security 35:1 (2010): 11.
- Snyder, Mearsheimer’s World, 158.
- Toft, John J. Mearsheimer, 403.
- See Kenneth N. Waltz, “International Politics Is Not Foreign Policy”, Security Studies 6:1 (1996): 54-57.
- Waltz, Theory of International Politics, 71-72 and 121-123.
- Toft, John J. Mearsheimer, 389.
- Mearsheimer, Tragedy of Great Power Politics, 422 note 60.
- Toft, John J. Mearsheimer, 401.
- Snyder, Mearsheimer’s World, 155.
- Mearsheimer, Tragedy of Great Power Politics 35-36.
- Snyder, Mearsheimer’s World, 155-156.
- Toft, John J. Mearsheimer, 393.
- Christopher Layne, “The Poster Child for Offensive Realism: America as a Global Hegemon”, Security Studies 12:2 (2002/2003): 127.
- Layne, The Poster Child for Offensive Realism, 129.
- David C. Hendrickson, “The Lion and the Lamb: Realism and Liberalism Reconsidered”, World Policy Journal 20:1 (2003): 97; Snyder, Mearsheimer’s World, 172.
- Kagan, Why John J. Mearsheimer is Right.
- Snyder, Mearsheimer’s World, 171-172.
- Toft, John J. Mearsheimer, 384.
- On Bargaining Theory see David A. Lake, “Two Cheers for Bargaining Theory: Assessing Rationalist Explanations of the Iraq War,” International Security 35:3 (2010/11): 15.
- Toft, John J. Mearsheimer, 396-397.
- Jonathan Kirshner, “The Tragedy of Offensive Realism: Classical Realism and the Rise of China”, European Journal of International Relations 18:1 (2010): 59-61.
- Toft, John J. Mearsheimer, 397.
- Colin Elman, “Extending Offensive Realism: The Louisiana Purchase and America’s Rise to Regional Hegemony”, American Political Science Review 98:4 (2004): 563.
- Snyder, Mearsheimer’s World, 173.
- .Layne, The Poster Child for Offensive Realism, 162-163.
- Toft, John J. Mearsheimer, 397-399.
- Feng, Liu and Zhang Ruizhuang. “The Typologies of Realism.” Chinese Journal of International Politics 1 (2006): 109-134.
- Hendrickson, David C. “The Lion and the Lamb: Realism and Liberalism Reconsidered.” World Policy Journal 20:1 (2003): 93-102.
- Kaplan, Robert D. “Why John J. Mearsheimer Is Right (About Some Things).” The Atlantic Magazine (2012). Accessed 13 April 2012. Available at: http://www.theatlantic.com/magazine/archive/2012/01/why-john-j-mearsheimer-is-right-about-some-things/8839/.
- Kirshner, Jonathan. “The Tragedy of Offensive Realism: Classical Realism and the Rise of China.” European Journal of International Relations 18:1 (2010): 53-75.
- Labs, Eric. “Beyond Victory: Offensive Realism and the Expansion of War Aims.” Security Studies 6:4 (1997): 1-49.
- Lake, David A. “Two Cheers for Bargaining Theory: Assessing Rationalist Explanations of the Iraq War.” International Security 35:3 (2010/11): 7-52.
- Layne, Christopher. “The Poster Child for Offensive Realism: America as a Global Hegemon.” Security Studies 12:2 (2002/2003): 120-163.
- Lee, Gerald Geunwook. “To be Long or Not to Be Long—That is the Question: The Contradiction of Time-Horizon in Offensive Realism.” Security Studies 12:2 (2002/2003): 196-217.
- Levy, Jack S. and William R. Thompson. “Balancing on Land and at Sea: Do States Ally Against the Leading Global Power?” International Security 35:1 (2010): 7-43.
- Lieber, Keir A. and Gerard Alexander. “Waiting for Balancing Why the World Is Not Pushing Back.” International Security 30:1 (2005): 109-139.
- Mearsheimer, John J. “The False Promise of International Institutions.” International Security 19:3 (1994-1995): 5-49.
- Mearsheimer, John J. The Tragedy of Great Power Politics. New York, NY: W.W. Norton, 2001.
- Mearsheimer, John J. “China’s Unpeaceful Rise.” Current History 105: 690 (2006): 160-162.
- Rynning, Sten and Jens Ringsmose. “Why Are Revisionist States Revisionist? Reviving Classical Realism as an Approach to Understanding International Change.” International Politics 45 (2008): 19-39.
- Shiping Tang. “From Offensive to Defensive Realism: A Social Evolutionary Interpretation of China’s Security Strategy.” In China's Ascent: Power, Security, and the Future of International Politics, edited by Robert Ross and Zhu Feng, 141-162. Ithaca, NY: Cornell University Press, 2008.
- Snyder, Glenn H. "Mearsheimer’s World—Offensive Realism and the Struggle for Security: A Review Essay." International Security 27:1 (2002): 149-173.
- Taliaferro, Jeffrey W. "Security Seeking Under Anarchy: Defensive Realism Revisited." International Security 25: 3 (2000/2001): 128-161.
- Toft, Peter. "John J. Mearsheimer: an offensive realist between geopolitics and power." Journal of International Relations and Development 8 (2005): 381-408.
- Waltz, Kenneth N. Theory of International Politics (Reading, MA: Addison-Wesley Publishing Company, 1979).
- Waltz, Kenneth N. "Realist Thought and Neorealist Theory." Journal of International Affairs 44:1 (1990): 21-37.
- Waltz, Kenneth N. "International Politics Is Not Foreign Policy." Security Studies 6:1 (1996): 54-57.
- Wang, Yuan-Kang. "Offensive Realism and the Rise of China." Issues & Studies 40:1 (2004): 173-201.
Further reading 
- Robert Giplin, War and Change in World Politics (Cambridge: Cambridge University Press, 1981).
- Randall L. Schweller, “Bandwagoning for Profit: Bringing the Revisionist State Back In”, International Security 19 :1 (1994): 72–107.
- Fareed Zarkaria, From Wealth to Power: the Unusual Origins of America’s World Role (Princeton: Princeton University Press, 1998).