The question of where Russia begins and ends—and who constitutes the Russian people—has preoccupied Russian thinkers for centuries. The collapse of the Soviet Union in 1991 and the Russian aggression against Ukraine in 2014 turned these concerns into a big “Russian question” that constitutes a world problem: What should be the relation of the new Russian state to its former imperial possessions—now independent post-Soviet republics such as Georgia, Armenia and Ukraine—and to the Russian and Russian-speaking enclaves in those republics? How should mental maps of Russian ethnicity, culture and identity be reconciled with the political map of the Russian federation?

These questions aren’t new. They first appeared on the political agenda in the course of the Russian Revolution, which upended more than 300 years of tsarist rule and gave birth to the modern concept of Russian nationhood. How exactly to define that new, post-imperial state precipitated a heated showdown between the two political titans trying to midwife the process: Vladimir Lenin and Joseph Stalin.

At the time, Lenin was the revered architect and elder statesman of the Bolshevik revolution, while Stalin was an ambitious rising party leader. Theirs was a clash not only of political vision and statecraft, but of personal insults and grudges. And while they hashed out the future of the nation, their battle would end not in resolution, but in Lenin’s premature death.

The conflict between the two leaders came to a head in the last days of December 1922, when 2,000 delegates from all over the former Russian empire gathered in the main hall of the Bolshoi Theatre in Moscow to create a new state, the Union of Soviet Socialist Republics. That state would include Russia, which was endowed with its own territory and institutions, distinct from those of the Union, and the already Soviet-ized republics of Ukraine, Belarus and Transcaucasia, which were formally independent of Russia.

The road to the formation of the Soviet Union began in April of that year in Rapallo, Italy, when the Bolsheviks signed their first international treaty with a Western power: Moscow and Berlin agreed renounce postwar financial claims on each other and opened the way to trade and economic cooperation. Georgy Chicherin, the Soviet Russian commissar for foreign relations, signed the document on behalf of the Russian republic, formed in July 1918. But he also attempted to sign on behalf of other Soviet republics, including Ukraine and Belarus, whose independence the Bolsheviks had been forced to recognize before overrunning them in 1919.

The strategy backfired.

According to the earlier agreement between Russia and the other Soviet republics, which was signed in the midst of revolution and civil war, the Russian authorities had no right to give orders to Ukrainian institutions without the Ukrainian government’s approval. Meanwhile, the Georgian communists also cried foul, insisting on their rights as the members of an independent republic. Ultimately, this overstep of Soviet Russia’s authority triggered the negotiations that resulted in the formation of the USSR.

In August 1922, Joseph Stalin and Sergo Ordzhonikidze, his right-hand man in the Caucasus (the region encompassing Georgia, Armenia and Azerbaijan, formed a special commission to recommend a new model of relations between the communist Party’s Central Committee, Russia and the republics. Stalin’s proposal, which he called the “autonomization of the republics,” was quite simple. The formally independent republics would be incorporated into the Russian Soviet Federation with rights of autonomy. The government bodies of the Russian Federation would become the central institutions of Soviet rule, exercising control over formally autonomous republics.

The republics rebelled. The Georgians led the charge against Stalin’s model, claiming the whole unification idea was premature. Ukrainians expressed a preference for the status quo. The Belarusians said they would mimic whatever model the Russians and the Ukrainians developed.

Stalin refused to budge and pushed ahead with his plan for autonomization—only to be stopped in his tracks by Lenin, who sided with the Georgians and Ukrainians. As far as he was concerned, the inclusion of the republics into the Russian Federation, especially against the will of their leaders, put the Russians in the position of imperial masters, undermining the idea of the voluntary union of nations—and making them little better than the tsarist empire they had overthrown.

Lenin’s broader concerns—about the worldwide unity of the working classes of all nationalities—colored his thinking about the future of the republics. In his mind, the survival of Soviet rule was closely linked with the success of world revolution, which depended on the rise of the working class in Germany, France and Britain, and then on the nationalist movements in China, India and Western colonies in Asia. If the revolution was to triumph on a global scale, those peoples’ desire for self-rule must be satisfied.

Instead of enlarging the Russian Federation, Lenin proposed creating a Union of Soviet Republics of Europe and Asia. The union would establish Russia and the existing formally independent republics as equals and develop all-Union government bodies separate from the Russian Federation’s.

Stalin, recognizing that an enlarged Russian Federation would create a poor image for the multinational communist state as a community of equals, proposed simply to turn the Russian government bodies into all-Union ones. As he saw it, there was no need for another level of bureaucracy. But Lenin wouldn’t back down: For him, the Union was a matter of principle, not expediency. Some way had to be found to accommodate rising non-Russian nationalism. But Stalin’s model proposed a return to the ethnic inequality of the past, which had already brought down the Russian Empire—and might topple the Soviet state as well.

Stalin backed down. Lenin’s authority in the Bolshevik Party was too great for him to question it openly. He agreed to adopt Lenin’s ideas as the basis for the creation of the Union, which was officially declared at the First All-Union Congress of Soviets on December 30, 1922.

But by the time the Congress was called to order, Lenin disappeared from sight. The 52-year-old leader of the Bolsheviks, who had fought tooth and nail for the creation of the Union, stayed put in his Kremlin apartment, a short walk from the Bolshoi Theatre, where the Congress was holding its sessions. It was a walk he couldn’t make. Eight days earlier, on December 12, he had suffered a major stroke and lost control of his right hand and leg.

The stroke occurred after Lenin’s heated conversation with Feliks Dzerzhinsky, the head of the secret police and a client of Stalin’s in the party leadership. Dzerzhinsky headed the commission that exonerated another supporter of Stalin’s, Sergo Ordzhonikidze, who had been sent to the Caucasus to crush local opposition to Stalin’s “autonomization” model and had beaten up a Georgian dissenter. Although Stalin and many of his supporters, such as Ordzhonikidze and Dzerzhinsky, were non-Russians (Stalin and Ordzonikidze hailed originally from Georgia, Dzerzhinsky from Poland), Lenin accused them of Russian chauvinism.

But the stroke prevented him from taking any decisive steps against them. Two days later, a commission of party officials, led by Stalin, placed strict limitations on Lenin’s activities, effectively isolating him. They said the restrictions were designed to prevent the worsening of Lenin’s health. But they also served a political purpose.

Barred from attending the congress and not trusting Stalin to fully implement his line, the paralyzed Lenin resolved to dictate his thoughts on the nationality question in a document to be passed on to the party leadership. Titled “On the Question of Nationalities or ‘Autonomization,’” it took the form of a letter and was completed the next day, December 31. In it, he attacked Stalin’s policies on the subject and criticized the rights provided to the republics by the Union treaty, deeming them inadequate to stop the rise of Great Russian nationalism, which he referred as “great-power chauvinism.” To Lenin, Russified non-Russians like Stalin and Ordzhonikidze were some of the worst offenders.

In Lenin’s view, Great Russian nationalists posed the main threat to the unity of state—not the regional nationalists, whom he hoped to accommodate by giving them local autonomy within the context of the Union. Lenin was prepared to replace the Union he had originally proposed with a looser association in which the centralized powers might be limited to defense and international relations alone. He felt that the republics’ right of secession, guaranteed by the Union treaty, might be an insufficient counterweight to Russian nationalism, and proposed that at the next congress the Union could be reformed to leave the center only with the aforementioned functions.

Stalin did his best to isolate Lenin from the rest of the leadership and keep his last letters secret. He even came into conflict with Lenin’s wife, Nadezhda Krupskaya, whom he accused of passing political news on to Lenin, thereby threatening Lenin’s peace of mind—and ultimately his health. Stalin insulted Krupskaia at one point by telling her, “We shall see what sort of wife of Lenin you are,” apparently hinting at Lenin’s past extramarital ties. When Lenin heard of it, he became furious and demanded an apology. Stalin wrote back saying he apologized, but did not know what Lenin wanted of him—he had just been protecting the leader from unnecessary stress.

Lenin’s stress level clearly increased when he learned that Stalin was stuffing the Chamber of Nationalities of the newly created Union parliament with his Russian supporters. Enraged, Lenin tried to enlist his fellow revolutionary leader Leon Trotsky’s support in his struggle against Stalin, but his call for help went unanswered. Lenin’s note of encouragement to Georgian Bolsheviks, dictated on March 6, 1923, turned out to be his last text ever. The next day, he suffered his third stroke, which left him permanently paralyzed. He died on January 21, 1924.

Ultimately, the Soviet Union, created in the midst of a battle between Lenin and Stalin, became a compromise between two visions and approaches. Stalin had to accept the federalist structure of the new state, but never gave up his “autonomization” scheme, which found its incarnation in the true backbone of Soviet rule—the Bolshevik Party. The Union was fully controlled from Moscow, and the republics’ parties had no more rights than regional party organizations in Russia. Russian institutions and identity dominated, forming the basis for much of the Union’s. The Russian Academy of Sciences, for example, would become an all-Union body.

Lenin didn’t get his way on the creating a loose union of the republics united only in military and foreign-policy terms. But he won on the issue of the structure of the Union—the collection of discreet republics—a victory that, ironically, would ultimately have greater consequences for the Russians than for the others. Lenin’s victory helped endow the Russians with a territory, institutions, population and identity distinct from those of the Union as a whole. In the state envisioned by Stalin, the Russians would have continued to share all those features with the empire, now renamed a Union. In Lenin’s state, they had no choice but to start acquiring an identity separate from the imperial one. Almost by default, Lenin became the father of the modern Russian nation, while the Soviet Union became its cradle.

Serhii Plokhy is the professor of history at Harvard University and the director of the university’s Ukrainian Research Institute. He is the author of numerous books, most recently, Lost Kingdom: The Quest for Empire and the Making of the Russian Nation and Chernobyl: The History of the Nuclear Catastrophe.

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