Who Caused the Ukraine War?

By John J. Mearsheimer

The question of who is responsible for causing the Ukraine war has been a deeply contentious issue since Russia invaded Ukraine on 24 February 2022.

The answer to this question matters enormously because the war has been a disaster for a variety of reasons, the most important of which is that Ukraine has effectively been wrecked. It has lost a substantial amount of its territory and is likely to lose more, its economy is in tatters, huge numbers of Ukrainians are internally displaced or have fled the country, and it has suffered hundreds of thousands of casualties. Of course, Russia has paid a significant blood price as well. On the strategic level, relations between Russia and Europe, not to mention Russia and Ukraine, have been poisoned for the foreseeable future, which means that the threat of a major war in Europe will be with us well after the Ukraine war turns into a frozen conflict. Who bears responsibility for this disaster is a question that will not go away anytime soon and if anything is likely to become more prominent as the extent of the disaster becomes more apparent to more people.

The conventional wisdom in the West is that Vladimir Putin is responsible for causing the Ukraine war. The invasion aimed at conquering all of Ukraine and making it part of a greater Russia, so the argument goes. Once that goal was achieved, the Russians would move to create an empire in eastern Europe, much like the Soviet Union did after World War II. Thus, Putin is ultimately a threat to the West and must be dealt with forcefully. In short, Putin is an imperialist with a master plan who fits neatly into a rich Russian tradition.

The alternative argument, which I identify with, and which is clearly the minority view in the West, is that the United States and its allies provoked the war. This is not to deny, of course, that Russia invaded Ukraine and started the war. But the principal cause of the conflict is the NATO decision to bring Ukraine into the alliance, which virtually all Russian leaders see as an existential threat that must be eliminated. NATO expansion, however, is part of a broader strategy that is designed to make Ukraine a Western bulwark on Russia’s border. Bringing Kyiv into the European Union (EU) and promoting a color revolution in Ukraine – turning it into pro-Western liberal democracy – are the other two prongs of the policy. Russia leaders fear all three prongs, but they fear NATO expansion the most. To deal with this threat, Russia launched a preventive war on 24 February 2022.

The debate about who caused the Ukraine war recently heated up when two prominent Western leaders – former President Donald Trump and prominent British MP Nigel Farage – made the argument that NATO expansion was the driving force behind the conflict. Unsurprisingly, their comments were met with a ferocious counterattack from defenders of the conventional wisdom. It is also worth noting that the outgoing Secretary General of NATO, Jens Stoltenberg, said twice over the past year that “President Putin started this war because he wanted to close NATO’s door and deny Ukraine the right to choose its own path.” Hardly anyone in the West challenged this remarkable admission by NATO’s head and he did not retract it.

My aim here is to provide a primer, which lays out the key points that support the view that Putin invaded Ukraine not because he was an imperialist bent on making Ukraine part of a greater Russia, but mainly because of NATO expansion and the West’s efforts to make Ukraine a Western stronghold on Russia’s border.

Let me start with the SEVEN MAIN REASONS to reject the conventional wisdom.

FIRST, there is simply no evidence from before 24 February 2022 that Putin wanted to conquer Ukraine and incorporate it into Russia. Proponents of the conventional wisdom cannot point to anything Putin wrote or said that indicates he was bent on conquering Ukraine.

When challenged on this point, purveyors of the conventional wisdom provide evidence that has little if any bearing on Putin’s motives for invading Ukraine. For example, some emphasize that he said Ukraine is an “artificial state“ or not a “real state.” Such opaque comments, however, say nothing about his reason for going to war. The same is true of Putin’s statement that he views Russians and Ukrainians as “one people“ with a common history. Others point out that he called the collapse of the Soviet Union “the greatest geopolitical catastrophe of the century.” But Putin also said, “Whoever does not miss the Soviet Union has no heart. Whoever wants it back has no brain.” Still, others point to a speech in which he declared that “Modern Ukraine was entirely created by Russia or, to be more precise, by Bolshevik, Communist Russia.” But that hardly constitutes evidence that he was interested in conquering Ukraine. Moreover, he said in that same speech: “Of course, we cannot change past events, but we must at least admit them openly and honestly.”

To make the case that Putin was bent on conquering all of Ukraine and incorporating it into Russia, it is necessary to provide evidence that 1) he thought it was a desirable goal, 2) he thought it was a feasible goal, and 3) he intended to pursue that goal. There is no evidence in the public record that Putin was contemplating, much less intending to put an end to Ukraine as an independent state and make it part of greater Russia when he sent his troops into Ukraine on 24 February 2022.

In fact, there is significant evidence that Putin recognized Ukraine as an independent country. In his well-known 12 July 2021 article dealing with Russian-Ukrainian relations, which proponents of the conventional wisdom often point to as evidence of his imperial ambitions, he tells the Ukrainian people, “You want to establish a state of your own: you are welcome!” Regarding how Russia should treat Ukraine, he writes, “There is only one answer: with respect.” He concludes that lengthy article with the following words: “And what Ukraine will be—it is up to its citizens to decide.” These statements are directly at odds with the claim that Putin wanted to incorporate Ukraine within a greater Russia.

In that same 12 July 2021 article and again in an important speech he gave on 21 February 2022, Putin emphasized that Russia accepts “the new geopolitical reality that took shape after the dissolution of the USSR.” He reiterated that same point for a third time on 24 February 2022, when he announced that Russia would invade Ukraine. In particular, he declared that “It is not our plan to occupy Ukrainian territory” and made it clear that he respected Ukrainian sovereignty, although only up to a point: “Russia cannot feel safe, develop, and exist while facing a permanent threat from the territory of today’s Ukraine.” In essence, Putin was not interested in making Ukraine a part of Russia; he was interested in making sure it did not become a “springboard“ for Western aggression against Russia.

SECOND, there is no evidence that Putin was preparing a puppet government for Ukraine, cultivating pro-Russian leaders in Kyiv, or pursuing any political measures that would make it possible to occupy the entire country and eventually integrate it into Russia.

Those facts fly in the face of the claim that Putin was interested in erasing Ukraine from the map.

THIRD, Putin did not have anywhere near enough troops to conquer Ukraine.

Let’s start with the overall numbers. I have long estimated that the Russians invaded Ukraine with at most 190,000 troops. General Oleksandr Syrskyi, the present commander-in-chief of Ukraine’s armed forces, recently said in an interview with The Guardian that Russia’s invasion force was only 100,000 strong. Indeed, The Guardian used that same number before the war started. There is no way that a force of either 100,000 or 190,000 could conquer, occupy, and absorb all of Ukraine into a greater Russia.

Consider that when Germany invaded the western half of Poland in September 1939, the Wehrmacht numbered about 1.5 million men. Ukraine is geographically more than 3 times larger than the western half of Poland was in 1939 and Ukraine in 2022 had almost twice as many people as Poland did when the German invaded. If we accept General Syrskyi’s estimate that 100,000 Russian troops invaded Ukraine in 2022, that means Russia had an invasion force that was 1/15th the size of the German force that went into Poland. And that small Russian army was invading a country that was much larger than Poland in terms of both territorial size and population.

Numbers aside, there is the matter of the quality of the Russian army. For starters, it was a military force largely designed to defend Russia from invasion. It was not an army primed to launch a major offensive that would end up conquering all of Ukraine, much less threatening the rest of Europe. Furthermore, the quality of the fighting forces left much to be desired, as the Russians were not expecting a war when the crisis began to heat up in the spring of 2021. Thus, they had little opportunity to train-up a skilled invasion force. In terms of both quality and quantity, the Russian invasion force was not close to being the equivalent of the Wehrmacht in the late 1930s and early 1940s.

One might argue that Russians leaders thought that the Ukrainian military was so small and so outgunned that their army could easily defeat Ukraine’s forces and conquer the entire country. In fact, Putin and his lieutenants were well-aware that the United States and its European allies had been arming and training the Ukrainian military since the crisis first broke out on 22 February 2014. Moscow’s great fear was that Ukraine was becoming a defacto member of NATO. Moreover, Russian leaders observed the Ukrainian army, which was larger than their invasion force, fighting effectively in the Donbass between 2014 and 2022. They surely understood that the Ukrainian military was not a paper tiger that could be defeated quickly and decisively, especially since it had powerful backing from the West.

Finally, over the course of 2022, the Russians were forced to withdraw their army from the Kharkiv oblast and from the western part of the Kherson oblast. In effect, Moscow surrendered territory that its army had conquered in the opening days of the war. There is no question that pressure from the Ukrainian army played a role in forcing the Russian withdrawal. But more importantly, Putin and his generals realized that they did not have sufficient forces to hold all the territory their army had conquered in Kharkiv and Kherson. So, they retreated and created more manageable defensive positions. This is hardly the behavior one would expect from an army that was built and trained to conquer and occupy all of Ukraine. Of course, it was not designed for that purpose and thus could not achieve that Herculean task.

FOURTH, in the months before the war started, Putin tried to find a diplomatic solution to the brewing crisis.

On 17 December 2021, Putin sent a letter to both President Joe Biden and NATO chief Stoltenberg proposing a solution to the crisis based on a written guarantee that: 1) Ukraine would not join NATO, 2) no offensive weapons would be stationed near Russia’s borders, and 3) NATO troops and equipment moved into eastern Europe since 1997 would be moved back to western Europe. Whatever one thinks of the feasibility of reaching a bargain based on Putin’s opening demands, which the United States refused to negotiate over, it shows that he was trying to avoid war.

FIFTH, immediately after the war began, Russia reached out to Ukraine to start negotiations to end the war and work out a modus vivendi between the two countries.

Negotiations between Kyiv and Moscow began in Belarus just four days after Russian troops entered Ukraine. That Belarus track was eventually replaced by an Israeli as well as an Istanbul track. All the available evidence indicates that the Russia was negotiating seriously and was not interested in absorbing Ukrainian territory, save for Crimea, which they had annexed in 2014, and possibly the Donbass. The negotiations ended when the Ukrainians, with prodding from Britain and the United States, walked away from the negotiations, which were making good progress when they ended.

Furthermore, Putin reports that when the negotiations were taking place and making progress, he was asked to remove Russian troops from the area around Kyiv as a good will gesture, which he did on 29 March 2022 . No government in the West or former policymaker has challenged Putin’s claim, which is directly at odds with the claim that he was bent on conquering all of Ukraine.

SIXTH, putting Ukraine aside, there is not a scintilla of evidence that Putin was contemplating conquering any other countries in eastern Europe.

Moreover, the Russian army is not even large enough to overrun all of Ukraine, much less try to conquer the Baltic states, Poland, and Romania. Plus, all those countries are NATO members, which would almost certainly mean war with the United States and its allies.

SEVENTH, hardly anyone in the West argued that Putin had imperial ambitions from the time he took the reins of power in 2000 until the Ukraine crisis started on 22 February 2014. At that point, he suddenly became an imperial aggressor. Why? Because Western leaders needed a reason to blame him for causing the crisis.  

Probably the best evidence that Putin was not seen as a serious threat during his first fourteen years in office is that he was an invited guest at the April 2008 NATO summit in Bucharest, which is where the alliance announced that Ukraine and Georgia would eventually become members. Putin, of course, was enraged by that decision and made his anger known. But his opposition to that announcement had hardly any effect on Washington because Russia’s military was judged to be too weak to stop further NATO enlargement, just as it had been too weak to stop the 1999 and 2004 waves of expansion. The West thought it could once again shove NATO expansion down Russia’s throat.

Relatedly, NATO enlargement before 22 February 2014 was not aimed at containing Russia. Given the sad state of Russian military power, Moscow was in no position to conquer Ukraine, much less pursue revanchist policies in eastern Europe. Tellingly, former US ambassador to Moscow Michael McFaul, who is a staunch defender of Ukraine and scathing critic of Putin, notes that Russia’s seizure of Crimea in 2014 was not planned before the crisis broke out; it was an impulsive move in response to the coup that overthrew Ukraine’s pro-Russian leader. In short, NATO expansion was not intended to contain a Russian threat, because the West did not think there was one.

It was only when the Ukraine crisis erupted in February 2014 that the United States and its allies suddenly began describing Putin as a dangerous leader with imperial ambitions and Russia as a serious military threat that NATO had to contain. This abrupt shift in rhetoric was designed to serve one essential purpose: to enable the West to blame Putin for the crisis and absolve the West of responsibility. Unsurprisingly, that portrayal of Putin gained much greater traction after Russia invaded Ukraine on 24 February 2022.

There is one twist on the conventional wisdom that bears mentioning. Some argue that Moscow’s decision to invade Ukraine has little to do with Putin himself and instead is part of an expansionist tradition that long predates Putin and is deeply wired into Russian society. This penchant for aggression, which is said to be driven by internal forces, not Russia’s external threat environment, has driven virtually all Russian leaders over time to behave violently toward their neighbors. There is no denying that Putin is in charge in this story or that he led Russia to war, but he is said to have little agency. Almost any other Russian leader would have acted the same way.

There are two problems with this argument. For starters, it is non-falsifiable, as the longstanding trait in Russian society that produces this aggressive impulse is never identified. Russians are said to have always been aggressive – no matter who is in charge – and always will be. It is almost as if it were in their DNA. This same claim was once made about Germans, who were often portrayed during the twentieth century as congenital aggressors. Arguments of this sort are not taken seriously in the academic world for good reason.

Furthermore, hardly anyone in the United States or Western Europe characterized Russia as innately aggressive between 1991 and 2014, when the Ukraine crisis broke out. Outside of Poland and the Baltic states, fear of Russian aggression was not a concern frequently voiced during those twenty-four years, which one would expect if the Russians were wired for aggression. It seems clear that the sudden appearance of this line of argument was a convenient excuse to blame Russia for causing the Ukraine war.  

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Let me shift gears and lay out the THREE MAIN REASONS to think that NATO expansion was the principal cause of the Ukraine war.

FIRST, Russian leaders across the board said repeatedly before the war started that they considered NATO expansion into Ukraine to be an existential threat that had to be eliminated.

Putin made numerous public statements laying out this line of argument before 24 February 2022. Speaking to the Defense Ministry Board on 21 December 2021, he stated: “what they are doing, or trying or planning to do in Ukraine, is not happening thousands of kilometers away from our national border. It is on the doorstep of our house. They must understand that we simply have nowhere further to retreat to. Do they really think we do not see these threats? Or do they think that we will just stand idly watching threats to Russia emerge?” Two months later at a press conference on 22 February 2022, just days before the war started, Putin said: “We are categorically opposed to Ukraine joining NATO because this poses a threat to us, and we have arguments to support this. I have repeatedly spoken about it in this hall.” He then made it clear that he recognized that Ukraine was becoming a defacto member of NATO. The United States and its allies, he said, “continue to pump the current Kiev authorities full of modern types of weapons.” He went on to say that if this was not stopped, Moscow “would be left with an ‘anti- Russia’ armed to the teeth. This is totally unacceptable.”

Other Russian leaders – including the defense minister, the foreign minister, the deputy foreign minister, and the Russian ambassador to Washington – also stressed the centrality of NATO expansion for causing the Ukraine crisis. Foreign Minister Sergei Lavrov made this point succinctly at a press conference on 14 January 2022: “The key to everything is the guarantee that NATO will not expand eastward.”

One often hears the argument that Russian fears were unfounded because there was no chance that Ukraine would join the alliance in the foreseeable future, if ever. Indeed, it is said that the United States and its European allies paid little attention to bringing Ukraine into NATO before the war. But even if Ukraine joined the alliance, that would not be an existential threat to Russia because NATO is a defensive alliance. Thus, NATO expansion could not have been a cause of the original crisis, which broke out in February 2014 or the war that began in February 2022.

This line of argument is false. In fact, the Western response to the events of 2014 was to double down on the existing strategy and draw Ukraine even closer to NATO. The alliance began training the Ukrainian military in 2014, averaging 10,000 trained troops annually over the next eight years. In December 2017, the Trump administration decided to provide Kyiv with “defensive weapons.” Other NATO countries soon got into the act, shipping even more weapons to Ukraine. Furthermore, Ukraine’s army, navy, and air force began participating in joint military exercises with NATO forces. The West’s effort to arm and train Ukraine’s military explains in good part why it fared so well against the Russian army in the first year of the war. As a headline in The Wall Street Journal from April 2022 put it, “The Secret of Ukraine’s Military Success: Years of NATO Training.” 

Putting aside the alliance’s ongoing efforts to make the Ukrainian military a more formidable fighting force that could operate alongside NATO troops, there was renewed enthusiasm in the West during 2021 for bringing Ukraine into NATO. At the same time, President Zelensky, who had never shown much enthusiasm for bringing Ukraine into the alliance and who was elected in March 2019 on a platform that called for working with Russia to settle the ongoing crisis, reversed course in early 2021 and not only embraced NATO membership for Ukraine, but also adopted a hardline approach toward Moscow.

President Biden, who moved into the White House in January 2021, had long been committed to bringing Ukraine into NATO and was a super-hawk toward Russia. Unsurprisingly, on 14 June 2021, NATO issued a communiqué at its annual summit in Brussels, which said: “We reiterate the decision made at the 2008 Bucharest Summit that Ukraine will become a member of the Alliance.” On 1 September 2021, Zelensky visited the White House, where Biden made it clear that the United States was “firmly committed” to “Ukraine’s Euro-Atlantic aspirations.” Then on 10 November 2021, Secretary of State Antony Blinken, and his Ukrainian counterpart, Dmytro Kuleba, signed an important document – the “US-Ukraine Charter on Strategic Partnership.” The aim of both parties, the document stated, is to “underscore … a commitment to Ukraine’s implementation of the deep and comprehensive reforms necessary for full integration into European and Euro-Atlantic institutions.” It also explicitly reaffirms the U.S. commitment to the “2008 Bucharest Summit Declaration.”

There appears to be little doubt that Ukraine was well on its way to becoming a member of NATO by the end of 2021. Even so, some supporters of this policy argue that Moscow should not have been concerned about that outcome, because “NATO is a defensive alliance and poses no threat to Russia.” But that is not how Putin and other Russian leaders think about NATO, and it is what they think that matters. In short, there is no question that Moscow saw Ukraine joining NATO as an existential threat that could not be allowed to stand.

SECOND, a substantial number of influential and highly regarded individuals in the West recognized before the war that NATO expansion – especially into Ukraine – would be seen by Russian leaders as a mortal threat and eventually lead to disaster.

William Burns, who now heads the CIA, but was the US ambassador to Moscow at the time of the April 2008 NATO summit in Bucharest, wrote a memo to then-Secretary of State Condoleezza Rice that succinctly describes Russian thinking about bringing Ukraine into the alliance. “Ukrainian entry into NATO,” he wrote, “is the brightest of all red lines for the Russian elite (not just Putin). In more than two and a half years of conversations with key Russian players, from knuckle-draggers in the dark recesses of the Kremlin to Putin’s sharpest liberal critics, I have yet to find anyone who views Ukraine in NATO as anything other than a direct challenge to Russian interests.” NATO, he said, “would be seen … as throwing down the strategic gauntlet. Today’s Russia will respond. Russian-Ukrainian relations will go into a deep freeze…It will create fertile soil for Russian meddling in Crimea and eastern Ukraine.”

Burns was not the only Western policymaker in 2008 who understood that bringing Ukraine into NATO was fraught with danger. Indeed, at the Bucharest summit, both German Chancellor Angela Merkel and French President Nicolas Sarkozy opposed moving forward on NATO membership for Ukraine because they understood it would alarm and infuriate Russia. Merkel recently explained her opposition: “I was very sure … that Putin is not going to just let that happen. From his perspective, that would be a declaration of war.”

To take this a step further, numerous American policymakers and strategists opposed President Clinton’s decision to expand NATO during the 1990s, when the decision was being debated. Those opponents understood from the start that Russian leaders would see it as a threat to their vital interests, and that the policy would eventually lead to disaster. The list of opponents includes prominent establishment figures like George Kennan, both President Clinton’s Secretary of Defense, William Perry, and his Chairman of the Joint Chiefs of Staff, General John Shalikashvili, Paul Nitze, Robert Gates, Robert McNamara, Richard Pipes, and Jack Matlock, just to name a few.

The logic of Putin’s position should make perfect sense to Americans, who have long been committed to the Monroe Doctrine, which stipulates that no distant great power is allowed to form an alliance with a country in the Western Hemisphere and locate its military forces there. The United States would interpret a move of that sort as an existential threat and go to great lengths to eliminate the danger. Of course, this is what happened during the Cuban Missile Crisis in 1962, when President Kennedy made it clear to the Soviets that their nuclear-tipped missiles would have to be removed from Cuba. Putin is deeply influenced by the same logic. After all, great powers do not want distant great powers moving into their backyard.

THIRD, the centrality of Russia’s profound fear of Ukraine joining NATO is illustrated by two developments that have occurred since the war began.

During the Istanbul negotiations that took place immediately after the invasion began, the Russians made it manifestly clear that Ukraine had to accept “permanent neutrality” and could not join NATO. The Ukrainians accepted Russia’s demand without any serious resistance, surely because they knew that it was otherwise impossible to end the war. More recently, on 14 June 2024, Putin laid out two demands that Ukraine would have to meet before he would agree to a ceasefire and the start of negotiations to end the war. One of those demands was that Kyiv “officially” state “that it abandons its plans to join NATO.”

None of this is surprising, as Russia has always seen Ukraine in NATO as an existential threat that must be prevented at all costs. That logic is the driving force behind the Ukraine war.

Finally, it is obvious from Russia’s negotiating position at Istanbul as well as Putin’s comments on ending the war in his 14 June 2024 address that he is not interested in conquering all of Ukraine and making it part of a greater Russia.

John J. Mearsheimer is the R. Wendell Harrison Distinguished Service Professor of Political Science at the University of Chicago, where he has taught since 1982.

This article was published on August 5, 2024 by John Mearsheimer at his personal Substack.

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