3. Offensive Realism and the Justification of War

Mearsheimer's theory does not just purport to explain Russia's aggression, but also to justify it

Professor Mearsheimer’s assignment of sole responsibility for the Ukraine war to the West will strike most people as, to put it politely, highly counter-intuitive—or, less politely, completely bonkers. How can the perpetrator of a major act of military aggression not bear at least some, if not all, responsibility for the widespread death and mayhem that it inevitably causes?

His answer is that, by aggressively expanding NATO into the post-Soviet space after the ending of the Cold War, and especially by even entertaining the possibility of Ukraine joining the alliance, the West intolerably provoked Russia—or as Mearsheimer likes to say, “we poked the bear.”

Note that Ukraine had not joined NATO at the time of Russia’s first attack in 2014 and had little prospect of so doing in the foreseeable future, as Mearsheimer himself acknowledged in a 2015 lecture (“and, by the way, NATO expansion is dead”). Until December 2014, Ukraine had a constitutional provision prohibiting the stationing of foreign forces on its soil or joining a military alliance. This was only repealed in response to Russia’s annexation of Crimea and incursion into the Donbass in February of that year, which resulted a huge change of Ukrainian public and political opinion about NATO membership.

Russia’s behaviour is completely contrary to international law, as well as the criteria of Just War Theory that provides the conceptual and philosophical underpinning of international law.

Not only that, it contravenes multiple treaties, agreements and conventions to which the Russian Federation and its precursor state, the Soviet Union, are signatories. This includes the Budapest Memorandum of 1994 in which Ukraine surrendered 1,800 nuclear weapons stationed on its soil to Russia in exchange for assurances from Russia (and the US and UK) that Ukraine’s sovereignty and territorial integrity within its 1991 borders would be respected, and the Russia-Ukraine Friendship Treaty of 1997 which gave the same undertakings.

Note also that Russia, and before it the Soviet Union, are signatories to several agreements, most relevantly the NATO-Russia Founding Act (1997) and the Helsinki Final Act (1975) that acknowledge the right of all states to enter into international agreements, including the right to join military alliances.

Moreover provocation, per se, is no justification for starting a war, any more than provocation is automatically a defence to murdering someone. According to Article 51 of the UN Charter the only “provocation” sufficient to justify recourse to military force, absent UN Security Council authorization, is an actual attack on the country concerned, which triggers the “inherent right” of all states to self-defence.

Since there is no evidence whatsoever that Ukraine, or NATO, had attacked Russia, or were remotely contemplating an attack, the Putin regime’s aggression is completely devoid of legitimate justification.

So, what does Mearsheimer have to say about all that?

In his lengthy tomes on international relations theory, there is scarcely any consideration of the legitimacy of state actions. He does not seem to think it matters. The nearest he comes to attempting to justify Russian behaviour in these terms is his claim that the 2022 invasion was a “preventive war” motivated by fear about the armaments and training provided to Ukraine by NATO countries that, he asserts, had turned Ukraine’s military into a de facto NATO army.

To prevent what? In international relations jargon, a distinction is made between a pre-emptive war, launched to forestall an imminent attack, for which there is concrete evidence of actual preparations being made, and a preventive war to prevent a danger that may emerge at some indeterminate future time. International legal scholars argue whether pre-emptive war can be legal, but there is virtual unanimity that preventive war is not. There is no evidence whatsoever that Ukraine, at the time of the invasion, had either the intention, or the capability, to attack its massively nuclear-armed neighbour.

So, how does Mearsheimer try to justify Russian conduct—and he does indeed justify it, not just explain it. To make sense of this it is necessary to consider the theoretical framework Mearsheimer has developed and elaborated over the past forty years. This is his version of realism, a theory that since World War II has been one of the most influential frameworks for analysing international issues.

Realism is most often counterpoised to liberal internationalism, which stresses the role of global institutions, international law, and an evolving set of norms that should govern how states behave towards each other, the “rules based international order”.

An important distinction between the two frameworks hinges on the relevance of the internal features of states to their external behaviour, how they interact with other states in the international system. This includes the system of governance, whether a state is a liberal democracy, a one-party dictatorship, a military junta, a “personalist” autocracy dominated by a single individual, like Putin’s Russia, or a theocracy led by a cabal of religious leaders, or a single individual like Iran’s Grand Ayatollah Khamenei.

For realists, these factors, as well as the characteristics of national leaders, their ambitions, ideological or religious commitments, propensity to take risks, hatreds and neuroses, moral scruples or lack thereof, have only limited effect on how states act, notwithstanding any stated motivations for what they do grounded in morality or ideology, such as the US aspiration to expand democratic governance in the leadup to the 2003 Iraq invasion, as expressed by then secretary of state Condoleezza Rice and others. These rationalizations, Mearsheimer contends, are generally misleading or hypocritical—a special peculiarity of the Anglo-Saxon mind according to Russian propagandists, and Mearsheimer (he likes to cite the British historian E.H. Carr on this).

No, for realists of all stripes, the most important factor is the structural nature of the international system. This effectively constrains what a state can do in any given situation. In Mearsheimer’s terms it locks them in an “iron cage”, severely limiting the scope for action motivated by morality or ideological preference. Mearsheimer acknowledges it is nice when morality and strategy point in the same direction, but if they conflict, he insists strategic considerations will, and should, prevail.

According to realists, the most important structural features are the anarchic nature of the international system, by which they mean that there is no higher authority above the nation state able to resolve conflicts between states, or as Mearsheimer likes to say, there is no 911 number they can call for help. The United Nations was supposed to fulfill this role, but has manifestly failed to do so, like its predecessor the League of Nations.

Moreover, we live in a world of uncertainty, where each state cannot be sure, given incomplete and unreliable information, about either the intentions or the capabilities of potential rivals, now or in future. Hence, for each state there will be a powerful incentive to gain sufficient power relative to others in order to ensure state security, indeed survival.

This is the cardinal principle of offensive realism, which Mearsheimer stresses is both a descriptive and a prescriptive theory:

 …it explains how great powers have behaved in the past and how they are likely to behave in the future. But it is also a prescriptive theory. States should behave according to the dictates of offensive realism, because it outlines the best way to survive in a dangerous world.

This poses the question of how much power is enough to best serve the security/survival imperative, and on this matter different variants of realism diverge. For the defensive realist school, enunciated by the earlier realist Kenneth Waltz, states aim should aim to acquire sufficient power to secure the existing status quo of interstate relations and power relativities.  

Defensive realists warn that the overly aggressive pursuit of power can be counterproductive, especially by inducing others to take countermeasures. Putin’s Russia provides a striking confirmation of this view, with the aggression against Ukraine prompting Sweden and Finland to overturn long-standing policies of military non-alignment and join NATO, with overwhelming support from their formerly sceptical populations.

This has added significant capability to the alliance, with Russian commentators complaining it will turn the Baltic Sea into a “NATO lake”. Furthermore, the admission of Finland has brought the NATO borders much closer to the Kola Peninsula where a large proportion of Russia’s strategic nuclear weapons are deployed.

Talk about a strategic own goal! In Chapter 9 it is argued that from the 1990s on the main motivator for states to seek membership of NATO, and the main impetus for NATO expansion, has been Russian behaviour, with Sweden and Finland’s decisions just the latest instance.

This is rather ironic given that, according to Mearsheimer’s offensive version of the realist theory, in order to ensure security and guarantee survival in this anarchic and uncertain world, states should seek to maximize their relative power, and this imperative remains up to the point where they become the local, or even global, hegemon.

Here is what Mearsheimer says in The Tragedy of Great Power Politics (2014 edition):

Offensive realism parts company with defensive realism over the question of how much power states want. For defensive realists, the international structure provides states with little incentive to seek additional increments of power; instead it pushes them to maintain the existing balance of power. Preserving power, rather than increasing it, is the main goal of states.

Offensive realists, on the other hand, believe that status quo powers are rarely found in world politics, because the international system creates powerful incentives for states to look for opportunities to gain power at the expense of rivals, and to take advantage of those situations when the benefits outweigh the costs. A state’s ultimate goal is to be the hegemon in the system.

In Mearsheimer’s view, states are compelled to pursue this goal by any means necessary, even military aggression where this is opportune. Indeed, he criticizes the defensive realist school for underrating the advantages of military force as an instrument of statecraft, subject to making correct judgements about the correlation of forces and other factors affecting the likelihood of success.

In The Tragedy of Great Power Politics, he illustrates these points by referring to the developing conflict between Germany and France in the first decades of the twentieth century. Germany, he argues, had the opportunity to become the hegemon of Europe in 1905, following France’s ally Russia’s catastrophic defeat in the Russo-Japanese war. Moreover, Britain at that time had not yet allied with France and Russia. From The Tragedy of Great Power Politics:

So France stood virtually alone against the mighty Germans, who “had an opportunity without parallel to change the European balance in their favor.” Yet Germany did not seriously consider going to war in 1905 but instead waited until 1914, when Russia had recovered from its defeat and the United Kingdom had joined forces with France and Russia.

He concludes:

According to offensive realism, Germany should have gone to war in 1905, because it almost surely would have won the conflict.

Germany should have started a war in 1905 because it had the chance to become hegemon of Europe! If this seems completely crazy, it is because it is, but it accords with the imperatives that states should act on according to Mearsheimer’s theory.

Presumably, back when things were more favourable to France a century earlier, when Napoleon successfully attacked and defeated Prussia in 1806 in the Battle of Jena-Auerstedt, and went on to take Berlin and occupy Prussia, making Napoleon the hegemon of Europe, that was right and proper too, following Mearsheimer’s logic.

What kind of a theory is this, which rationalizes a military free-for-all to any power that thinks it can get away with a power-grab to improve its position? Yet, this is the basis on which Mearsheimer thinks “rational” policymakers should act. It is a grotesquely amoral rationale for wars of territorial conquest by powerful states, an aggressor’s charter.

There is a certain irony here, given Mearsheimer’s justification for this type of power grab as a mechanism for dealing with uncertainty in an anarchic international state system. There are few things more prone to uncertainty and unpredictable outcomes than wars, even when an aggressor has a high level of confidence of success, as Hitler and the Japanese militarists discovered in World War II. It didn’t work out too well for Mussolini either when both he and his mistress ended their days strung up by their feet by Italian partisans.

As the Prussian strategist Moltke the Elder observed, “no plan of operations extends with certainty beyond the first encounter with the enemy”, a principle that Putin’s military leaders Sergei Shoigu and Valery Gerasimov could no doubt attest to after the disastrous failure of their opening plan of operations in Ukraine.

So, even absent any moral scruples about warmongering, sheer self-interest—indeed survival—would  seem to militate against state leaders following the principles of offensive realism. Maybe it would be a lot safer, from both a state and personal point of view, to try and secure acceptance of some decent norms and understandings when it comes to war and peace. Something like a “rules based international order” perhaps?

Given Mearsheimer’s framework, Putin’s brutal assaults on Ukrainian sovereignty and territorial integrity were not only rational and predictable, but in a peculiar Mearsheimerian sense, even righteous.

As he says, in How States Think:

The fact is that Putin and his advisers thought in terms of straightforward balance-of-power theory, viewing the West’s efforts to make Ukraine a bulwark on Russia’s border as an existential threat that could not be allowed to stand.

However, according to Mearsheimer’s prescriptive theory, he need not have even bothered with the “existential threat” claim which, as discussed in detail later, was completely spurious anyway. Given the logic above, it would be sufficient justification for Putin to think that he could get away with conquering Ukraine, just to add some increment to his relative power.

Likewise, it would have been perfectly justifiable for him to conquer the other post-Soviet states to secure his position as regional hegemon, were it not for the complication that they were now in NATO and therefore, as Mearsheimer said to The New Yorker’s correspondent Isaac Chotiner, out of his reach, which Mearsheimer says is a bad thing.

Notice that Mearsheimer simply asserts that Putin was motivated solely by balance-of-power concerns, dismissing out of hand any suggestion that he may have had ambitions to reconstitute Russia as an imperial power. In fact, there is overwhelming evidence, described in Chapter 8, that Putin has had just such aspirations for a considerable time, and that they became a central priority for him from the start of his third presidential term in 2012. According to some of his closest advisers, these aspirations go back much earlier.

But what difference would it make, given Mearsheimer’s theory of what motivates states? Given the “grab what you can” injunction inherent in offensive realism, territorial expansion becomes an imperative anyway, whether accompanied by fantasies about restoring Russia’s imperial greatness or not.

Based on Mearsheimer’s reasoning, Putin’s regime should aim to be the hegemon in Europe; the CCP regime in China should aim for hegemonic status in the Indo-Pacific region, and ultimately the world; Iran should seek to be the hegemon in the Middle East. Even tinpot dictators like Venezuela’s Nicolás Maduro should aim to be a mini hegemon in Central America by annexing most of a neighbouring country, as he is trying to do now. And the US and its allies should try to counter these power grabs. Makes for a bit of a powder keg, doesn’t it.

Yet, Mearsheimer thinks the world will be a better place when states behave this way. As for any relatively powerless countries in the penumbra of larger powers that harbour illusions they have a right to meaningful sovereignty, including choosing their own system of government, sorry—you are out of luck. Offensive realism is a theory for great powers only—recall the title of his book The Tragedy of Great Power Politics.

As noted above, even if all Mearsheimer’s talk about the grave threat to Russia from NATO expansion were true, and it is not, this would not go close to providing a valid casus belli, a legitimate justification for war according to international law. Article 51 of the UN Charter stipulates that recourse to war is legal only if a state is exercising its inherent right to self-defence following an actual attack, or if it is acting pursuant to a resolution of the UN Security Council. There is debate about the case when a war is launched in response to clear evidence of an imminent attack, the pre-emptive war case.

Mearsheimer readily concedes that Russia’s invasion of Ukraine contravenes international law, and the norms of Just War Theory. Yet, he insists that it was nonetheless justified. He discussed this issue in a September 2023 interview with Gavin Jacobson of New Statesman magazine:

I [Jacobson] asked if it could be considered a “just war”? “Russia’s invasion of Ukraine was a preventive war,” he said, “which is not permissible according to Just War Theory. But Russian leaders certainly saw the invasion as ‘just’, because they were convinced that Ukraine joining NATO was an existential threat that had to be eliminated. Almost every leader on the planet would think that a preventive war to deal with a threat to its survival was ‘just’.”

The normal understanding of a preventive war is one that is launched to prevent a possible attack sometime in the future, in contrast to a pre-emptive war to forestall an imminent attack. There is no dispute that preventive wars are illegal according to international law.

Mearsheimer elaborates on his thinking about the relationship between strategy, international legality, and morality, in a paper titled War and International Politics for the Notre Dame International Security Center on 30 January, 2024. He expanded on the themes of this paper in a lecture with the same title posted on YouTube two weeks later.

The lecture is useful in that it brings together in a concise format his views  on the circumstances where recourse to war is justified. He invokes  the Prussian general and military theorist Carl von Clausewitz to argue that war, being the continuation of politics by other means, should be seen as a legitimate tool of statecraft, to be used much more permissively than allowed by present-day international law and Just War Theory.

Mearsheimer sums up his viewpoint on the justifications for war in the following passage from the paper:

In keeping with international law and contemporary just war theory, most people in the West who think seriously about this issue believe that starting a war is only acceptable under a narrow set of circumstances: 1) if a country has good evidence that it is about to be attacked by an adversary and it launches a pre-emptive strike. In other words, it gets in the first blow in a war that is bound to happen; 2) if a state secures permission from the UN Security Council to attack another state; and 3) if one country intervenes in another to prevent mass murder or genocide.

According to the dictates of both international law and just war theory, preventive wars, which are wars aimed at averting an adverse shift in the balance of power, are verboten. They are illegal or unjust. So are wars of opportunity, where the balance of power is not shifting against the initiator, but it sees an opening to gain more power and enhance its security or perhaps achieve some other political objective like spreading an ideology. Thus, whether you see Putin’s invasion of Ukraine as a preventive war, as Naftali Bennett, Nicolas Sarkozy, and Jens Stoltenberg do, or you see it as an unprovoked war of aggression, as most people in the West do, it is both illegal and unjust, and should be condemned.27

In essence, many contemporary Western thinkers reject Clausewitz’s famous dictum that war is an extension of politics by other means. For him, war is simply a useful tool of statecraft that states employ whenever it makes good military and political sense. That perspective allows for launching preventive wars as well as wars of opportunity. Naturally, there is no room for moral or legal considerations in Clausewitz’s understanding of war, which puts it at odds with how most people in the West think about war initiation.

The first paragraph of this excerpt contains a couple of inaccuracies in how he describes the criteria of international law and Just War Theory. Article 51 of the UN Charter states war is justified in only two circumstances: when exercising the inherent right to self-defence in response to an actual attack; and when authorized by the UN Security Council. Contrary to Mearsheimer, the Charter does not legitimize pre-emptive war, though there is debate among scholars about whether it is a reasonable interpretation of the inherent right to self-defence.

In his earlier writings and lectures, and in this lecture, Mearsheimer argues that nation states concerned about their security and survival inevitably will, and should, be prepared to breach international law and the moral norms of Just War Theory (moral and philosophical underpinning of international law) if they are sufficiently threatened.

Consequently, Mearsheimer thinks states should be open to waging two additional types of war, both strictly prohibited under international law: preventive wars, and wars of opportunity.

In the lecture, Mearsheimer defines a preventive war as one that is “aimed at averting an adverse shift in the balance of power.” As discussed in his War and International Politics lecture, this is Mearsheimer’s defence of Putin’s invasion of Ukraine as both rational, according to offensive realism, and warranted. This was because NATO expansion, and especially the prospect of Ukraine joining, caused just such an adverse shift.

This begs the question: how big a shift in the strategic balance would warrant going to war?

Would a neighbouring state increasing its military capabilities warrant going to war? That would undoubtedly change the strategic balance, but nobody, probably even Mearsheimer, would suggest that absent evidence of aggressive intentions, that could justify going to war. If it did, the United States would have been justified in attacking China decades ago when it became apparent that it aimed to match American naval capabilities.

Recognizing this, Mearsheimer needs to add an additional claim: that NATO expansion posed such a severe risk to Russia’s survival, an existential risk, that going to war was justified to counter it. Here is what he says in the paper, echoing his earlier comment to Jacobson:

Consider the Russian invasion of Ukraine. It was a preventive war, which is impermissible according to both just war theory and international law. But Russian leaders surely believe the invasion was just or at least justifiable because they are convinced that Ukraine joining NATO is an existential threat that must be prevented. I believe that almost every world leader would think that a preventive war aimed at eliminating a mortal threat is a just or morally correct decision, even if just war theory says it is not.

I will not rehearse in detail the arguments made in Chapter 7 as to why this “existential risk” claim is ridiculous and indefensible. Russia has signed agreements that acknowledge the right of all states to join alliances, including military ones. Mearsheimer adds a footnote reference to a speech Putin made three days before the invasion that acknowledges that right but adds the stipulation that doing so should not “pose a threat to other states.” Ukraine had not joined NATO and had little prospect of joining it other than possibly in the distant future.

Moreover, there is no evidence that NATO has ever contemplated attacking Russia, holder of the world’s largest stock of nuclear weapons. They would be crazy to even contemplate such an act. As discussed in Chapter 9, the former Soviet bloc states were desperate to join NATO because of vastly more justified existential fears prompted by disturbing Russian conduct dating back to the early Yeltsin years.

Recall that in 1994 Ukraine agreed to surrender all the Soviet nuclear weapons on its soil to Russia in exchange for assurances from Russia (and the US and the UK) that it would respect Ukraine’s sovereignty and territorial integrity within its 1991 borders. Mearsheimer has acknowledged that had Ukraine decided to hang on to these weapons, it would have effectively been immunised against Russian attack.

In the paper and lecture, Mearsheimer contends that preventive wars and wars of opportunity, despite both being illegal according to the stipulations of international law and unjust according to the norms of Just War Theory, are nevertheless in his view justified by the imperative of ensuring state survival.

Which raises an obvious question: how does he justify this form of justification? Here is what he says on the question in his February 2024 lecture:

What is going on here, however, is more than just a disagreement: the aim of just war theorists and champions of international law is to subordinate the conduct of international politics to a moral or legal order that dictates when states can start a war as well as how they should wage it. Simply put, they want to create a world where initiating a war is permissible only in narrowly bounded circumstances.

But this is not how the world works. Preventive wars and wars of opportunity are baked into international politics, and nothing is going to change that fact of life in the foreseeable future. Whether states are democracies or non-democracies, they will launch these kinds of wars if they conclude that it is in their strategic interest to do so.

You could call this the argument from inevitability, but it is an obvious fallacy. Preventive wars and wars of opportunity are inevitable; therefore, they are justified, an obvious non sequitur. Why not cut to the chase and say that wars are inevitable, so there is no point trying to minimize them. Or, for that matter, crime is inevitable, so why combat it, and so on and so forth.

The whole point of instituting a rules-based international order, along with sanctions against violating them, is to diminish the incidence of wars, especially those of the type Mearsheimer defends. Talk of such wars being “baked into” international politics presumes the world is immutable. Mearsheimer offers no justification for this claim.

The history of post-war Western Europe provides a telling refutation of this fatalistic attitude. Britain, Germany, France, and other states had been at each other’s throats for centuries. Yet when they all became liberal democracies, the prospect of war between them became inconceivable, even if they continue to squabble about all manner of things. They lend powerful evidence for the “democratic peace” argument, that Mearsheimer disparages in The Tragedy of Great Power Politics, citing a study that actually strongly confirms it.

But then he draws on what he believes to be his trump card: mortal threats, threats that endanger the survival of the state—existential dangers. Ensuring state survival, he contends, is the supreme obligation of the leaders of every state.

Not necessarily. He falsely analogizes states with people. People cannot fulfil any of their other goals if they fail to survive. Ditto states, argues Mearsheimer. But states, as such, do not have goals, nor a “will to life”. It is perfectly possible for the people of a state, and indeed their leaders, to be in favour of abolishing a state structure of which they are subjects, in pursuit of a better life, or indeed of greater security. The people and government of the GDR (the old East Germany) cheerfully assented to the termination of that state’s existence in 1990 and absorption into the Federal Republic. Scotland, likewise, abolished itself as a separate state to become part of the United Kingdom in 1707.

Mearsheimer becomes quite excited at the discovery that even Michael Walzer, the liberal American political scientist, author of the magisterial Just and Unjust Wars, and strong defender of the Just War Theory approach, concedes in this book that the rules of war can be violated when a state is confronted with a “danger of an unusual and horrifying kind”, but qualifies that by adding it must wait until it is “face-to-face not merely with a defeat likely to bring disaster to a political community” before it can act unjustly.

To which Mearsheimer replies:

Why would a state facing an existential threat wait until the moment when it is on the verge of destruction to act like a realist? Would it not make more sense for a state to deal with a rival before it became a mortal threat? Obviously, it would, but that logic pushes states to act according to realist dictates from the get-go and ignore just war theory unless it is in synch with balance-of-power logic.

In essence, the survival imperative in international anarchy leaves states with little choice but to see preventive wars and wars of opportunity as acceptable tools of statecraft. Indeed, if a state strictly adhered to just war theory or international law, it would put its survival at risk.

What Mearsheimer’s formulation fails to consider is that, if his thinking is taken to license starting wars based on any future hypothetical threat scenario, however improbable or implausible, it will amount to a recipe for more wars, endless wars of prevention and opportunity, each with serious risks, including disastrous escalation

Russia’s invasion of Ukraine makes the point perfectly. Russia started a war, ostensibly to ward off a potential future threat from NATO, in reality a vanishingly low-probability event. However, this course of action is far from riskless. How many regimes and empires, and nations, have gone under after initiating wars? And nowadays, any such undertaking carries the risk of catastrophic risk of escalation, as Putin’s incredibly irresponsible nuclear brinkmanship illustrates. There is serious talk of Russian failure in Ukraine possibly leading to the breakup of Russia.

In addition to which, there is the objection of “defensive” school realists that such conduct will inevitably trigger a reaction from countries who feel threatened by it. Sweden and Finland’s decision to overturn long-standing policies of military non-alignment and join NATO in response to Russian aggression illustrates the point perfectly.

If, counterfactually, NATO is a dire threat to Russia, it is now a bigger one, with the Baltic Sea now a “NATO lake”, and NATO’s Finland frontier perilously close to the Kola Peninsula, where many of Russia’s strategic nuclear weapons are housed. Ukraine, likely to survive in some form, has gone from a nation marked by generally friendly attitudes to Russia to one that imbued with a burning hatred for all things Russian, likely to last for generations.

Across the board, NATO member nations, especially “frontline” states near to Russia, including Poland, the Baltic nations, Finland, and Sweden, have all markedly ramped up their defence spending in preparation for what they see as a possible future war between Russia and NATO.

Some wag on X (Twitter) summed it up by posting a spoof gold medallion signed by NATO secretary-general Jens Stoltenberg awarded to Vladimir Putin for services helping to build the alliance.

One thing people cannot accuse Mearsheimer of is shying away from the atrocious policy prescriptions that arise from his offensive realism theory. It legitimates the use of military force by any power that finds it opportune to do so, and is prepared to assert, however tenuously, that its survival is on the line.

Where could this thinking lead? After all, in How States Think Mearsheimer notes that, according to the CCP regime, an independent Taiwan would be a:

threat to China’s survival because it represents the permanent loss of national territory

All 0.17 percent of it—talk about a non sequitur! It seems that, for Mearsheimer, the threshold for declaring an issue “existential”, and therefore warranting war, is very low indeed.

Mearsheimer has had a great deal to say about the Ukraine war ever since it first became kinetic back in 2014. Since 7 October 2023, he has also had a lot to say about the war between Israel and Hamas triggered by Hamas’s murderous terrorist attack on that date.

When it comes to Ukraine, everything he has had to say has been framed as an application of his broader theory of international relations, his offensive realism theory, which stipulates that states must give absolute priority to ensuring their own security and survival, including by waging preventive wars, or even wars of opportunity.

As to the legality and morality of the state conduct arising from this priority, its legitimacy according to the norms of the rules-based international order, Mearsheimer is frankly not very interested. If you search his major texts, you will find scarcely any serious discussion of, or even references to the legitimacy of state conduct, which even many other prominent realists regard as important.

As for morality, Mearsheimer is prepared to accord it some weight, but only provided it does not conflict with the strategic imperatives of offensive realism—state security and survival—in pursuit of which he contends states must be coldly rational in their application of these general principles. A rational actor in the international sphere is, for Mearsheimer, a homo theoreticus, someone who applies a sound theory (especially his own) when deciding policy.

Yet, astonishingly, when it comes to the Israel-Hamas war that broke out with Hamas’s terrorist onslaught on 7 October 2023, about which he has had much to say, all his theorizing seems to vanish into thin air. Search his many contributions, many of which are on YouTube (which has a useful feature to automatically generate a transcript of any video) and the only time offensive realism, or realism in general, comes up in discussions about the Gaza war is if he is specifically queried about it by an interlocuter.

This is all the more perverse given the fact that Israel faces a genuinely existential threat from a coalition of enemy entities, backed and co-ordinated by Iran, that openly and explicitly declare their intention to annihilate Israel and slaughter its Jewish population.

Mearsheimer becomes quite tetchy on the rare occasions when he is pressed about this inconsistency, as in the interview below with Freddie Sayers, editor of the online magazine UnHerd. His take on Gaza is considered in detail in a Chapter 11.