He had initially been part of the country's informal collective leadership with Lev Kamenev and Grigory Zinoviev after the death of Vladimir Lenin in 1924, but consolidated his power within the party and state, especially against the influences of Leon Trotsky and Nikolai Bukharin, in the mid-to-late 1920s.

Prior to the October Revolution of 1917, Stalin was a revolutionary who had joined the Bolshevik faction of the Russian Social Democratic Labor Party (RSDLP) led by Vladimir Lenin, in 1903.

Stalin was one of the Bolsheviks' chief operatives in the Caucasus and grew closer to Lenin, who saw him as tough, loyal, and capable of getting things done behind the scenes.

Prior to the Revolution, Trotsky frequently snubbed Stalin, mocked his lack of education, and questioned his effectiveness as a revolutionary.

Before his 1913-1917 exile in Siberia, Stalin was one of the Bolshevik operatives in the Caucasus, organizing cells, spreading propaganda, and raising money through criminal activities.

[14] According to Montefiore, Stalin socialised with hitmen “Kamo and Tsintsadze" but issued formal commands to the rest of the Outfit members through his bodyguard.

In the Russian Civil War that followed, Stalin forged connections with various Red Army generals and eventually acquired military powers of his own.

After winning the Civil War, the Bolsheviks moved to expand the Revolution into Europe, starting with Poland, which was fighting the Red Army in Ukraine.

Fearing a backlash from the trade unions, Lenin asked Stalin to build a support base in the Workers' and Peasants' Inspectorate (Rabkrin) against bureaucratism.

Stalin still held his posts in the Orgburo, the Workers' and Peasants' Inspectorate and the Commissariat for Nationalities Affairs, though he agreed to delegate his workload to subordinates.

[18] On 25 May 1922, Lenin suffered a stroke while recovering from surgery to remove a bullet lodged in his neck since a failed assassination attempt in August 1918.

Historian Stephen Kotkin assesses that Krupskaya, working in tandem with Trotsky, may have written it in an effort to discredit Stalin and remove him from his role in the government.

While the triumvirate remained intact throughout 1924 and the early months of 1925, Zinoviev and Kamenev did not regard Stalin highly as a revolutionary theorist, and often disparaged him in private even as they had aided him publicly against Trotsky and the Left Opposition.

Zinoviev and Kamenev suddenly found themselves in a minority at the Fourteenth Party Conference in April 1925, over their belief that socialism could only be achieved internationally, which resulted in the triumvirate splitting up.

[32][33] However, Trotsky's opposition and criticism of the ruling troika received support from several, Central Committee members of foreign communist parties.

[38] Stalin believed that the KMT bourgeoisie, together with all patriotic national liberation forces in the country, would defeat the western imperialists in China.

[41][42] While the catastrophic events in China completely vindicated Trotsky's criticism of Stalin's approach towards the Chinese Revolution, this paled insignificance compared to the demoralization that the Soviet masses felt at such a big setback for socialist revolution in China, with this demoralization aiding Stalin and his allies in the Communist Party and the Soviet state.

On 7 November 1927, on the tenth anniversary of the October Revolution, the United Opposition held a demonstration in Red Square, Moscow, along with Vladimir Lenin's widow, Nadezhda Krupskaya.

While Trotsky remained firm in his opposition to Stalin after his expulsion from the Communist Party and his subsequent exile, Zinoviev and Kamenev capitulated almost immediately and called on their supporters to follow suit.

After the United Opposition was prohibited in December 1927, the Kulaks and NEPmen were emboldened and exerted much greater economic pressure on the Soviet government in the months afterwards.

[18][43] Bukharin criticized Stalin's plans for rapid industrialization financed by kulak wealth, and advocated a return to Lenin's NEP.

[50] Stalin dominated the Politburo (the policy-making branch of the Communist Party) through staunch allies such as Sergo Ordzhonikidze, Lazar Kaganovich, Vyacheslav Molotov, and Kliment Voroshilov.

The death of this popular, high-profile politician shocked Russia, and Stalin used this murder to begin The Great Terror.

[51] Lev Kamenev and Zinoviev were arrested and, to escape long prison sentences, confessed to political and moral responsibility for Kirov's murder.

[55] As in claimed by Montefiore, in July 1936, Stalin promised Kamenev and Zinoviev (through NKVD chief, Genrikh Yagoda) that there would be no executions or persecution of their families if they confessed to conspiring with Trotsky.

Marshal Mikhail Tukhachevsky and the senior Red Army military officers Iona Yakir, Ieronim Uborevich, Robert Eideman, August Kork, Vitovt Putna, Boris Feldman and Vitaly Primakov (as well as Yakov Gamarnik, who committed suicide before the investigations began) were accused of anti-Soviet conspiracy and sentenced to death; they were executed on the night of 11 to 12 June 1937, immediately after the verdict delivered by a Special Session (специальное судебное присутствие) of the Supreme Court of the USSR.

[62] According to Trotskyist historian Vadim Rogovin, Stalin also had suppressed thousands of foreign communists capable of leading socialist change in their respective countries.

[71] Contrarily, certain political theorists such as Trotsky have emphasised the role of external conditions in facilitating the growth of a Soviet bureaucracy which served as a power base for Stalin.

[72] Other historians have regarded the premature deaths of prominent Bolsheviks such as Vladimir Lenin and Yakov Sverdlov to have been key factors in his elevation to the position of leadership in the Soviet Union.

In part, because Sverdlov served as the original chairman of the party secretariat and was considered a natural candidate for the position of General Secretary.