At the Second Congress of the Social Democratic Labour Party in London in 1903, there was a dispute between Vladimir Lenin and Julius Martov, two of SDLP's leaders. Lenin argued for a small party of professional revolutionaries with a large fringe of non-party sympathizers and supporters. Martov disagreed believing it was better to have a large party of activists.
Julius Martov based his ideas on the socialist parties that existed in other European countries such as the British Labour Party. Lenin argued that the situation was different in Russia as it was illegal to form socialist political parties under the Tsar's autocratic government. At the end of the debate Martov won the vote 28-23 . Vladimir Lenin was unwilling to accept the result and formed a faction known as the Bolsheviks. Those who remained loyal to Martov became known as Mensheviks.
Gregory Zinoviev, Anatoli Lunacharsky, Joseph Stalin, Mikhail Lashevich, Nadezhda Krupskaya, Mikhail Frunze, Alexei Rykov, Yakov Sverdlov, Lev Kamenev, Maxim Litvinov, Vladimir Antonov, Felix Dzerzhinsky, Gregory Ordzhonikidze and Alexander Bogdanov joined the Bolsheviks. Whereas George Plekhanov, Pavel Axelrod, Leon Trotsky, Lev Deich, Vladimir Antonov-Ovseenko, Boris Nicolaevsky, David Dallin, Vera Zasulich, Irakli Tsereteli, Moisei Uritsky, Noi Zhordania and Fedor Dan supported Julius Martov.
The SDLP journal, Iskra remained under the control of the Mensheviks so Vladimir Lenin, with the help of Anatoli Lunacharsky, Alexander Bogdanov, Lev Kamenev and Gregory Zinoviev, established a Bolshevik newspaper, Vperyod. The Mensheviks played a leading role in the 1905 Revolution and were particularly active in the soviets and the emerging trade union movement.
In 1911 the Bolsheviks made plans to capture control of the Social Democratic Labour Party at the conference to be held in Prague in January, 1912. This move was unsuccessful and the party split and after that date the Mensheviks split completely from the Bolsheviks. Most Mensheviks condemned Russia's involvement in the First World War but a small minority supported Nicholas II and his government.
Robert V. Daniels, the author of Red October: The Bolshevik Revolution of 1917 (1967) has argued: "Between Lenin and the Mensheviks the basic difference was more temperamental than doctrinal. The Mensheviks, like many earlier critics of Russian injustice, were idealists driven by sympathy for the masses but disinclined to conspire and fight; they admired Western democratic socialism and hoped for a peaceful and legal path to social reform once the Russian autocracy was overthrown. They were appalled by Lenin's elastic political morality and the philosophy they termed 'dictatorship over the proletariat.' It is impossible to escape the very strong suspicion that Lenin's deepest motive was the drive for personal power, however he might have rationalized it."
When Lenin returned to Russia on 3rd April, 1917, he announced what became known as the April Theses. Lenin attacked those Bolsheviks who had supported the Provisional Government. Instead, he argued, revolutionaries should be telling the people of Russia that they should take over the control of the country. In his speech, Lenin urged the peasants to take the land from the rich landlords and the industrial workers to seize the factories. Some Mensheviks such as Leon Trotsky and Alexandra Kollontai, agreed with this view and now joined the Bolsheviks.
Against the wishes of their leader, Julius Martov, two Mensheviks, Irakli Tsereteli and Fedor Dan joined the Provisional Government in May 1917. Tsereteli, who was the government's Minister of the Interior, gave the order to arrest Lenin, Leon Trotsky and other revolutionaries in July, 1917.
The Mensheviks dramatically lost the support of the Russian people during the events of 1917. In the elections for the Constituent Assembly in November, 1917, they obtained 1,700,000 votes compared to the Bolsheviks (9,000,000) and the Socialist Revolutionaries (16,500,000).
Julius Martov and the Mensheviks were united in their opposition to the October Revolution. Most of them supported the Red Army against the White Army during the Russian Civil War, however, they continued to denounce the persecution of liberal newspapers, the nobility, the Cadets and the Socialist Revolutionaries. The Mensheviks, along with other opposition parties, were banned after the Kronstadt Rising.