<Tr> <Td> </Td> <Td> This section needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2012) (Learn how and when to remove this template message) </Td> </Tr> <P> As the Russian Revolution of 1905 progressed, Bolsheviks, Mensheviks and smaller non-Russian social democratic parties operating within the Russian Empire attempted to reunify at the Fourth (Unification) Congress of the RSDLP held at Folkets hus, Norra Bantorget in Stockholm, April 1906 . When the Mensheviks struck an alliance with the Jewish Bund, the Bolsheviks found themselves in a minority . </P> <P> However, all factions retained their respective factional structure and the Bolsheviks formed the Bolshevik Centre, the de facto governing body of the Bolshevik faction within the RSDLP . At the Fifth Congress held in London in May 1907, the Bolsheviks were in the majority, but the two factions continued functioning mostly independently of each other . </P> <P> Tensions had existed between Lenin and Bogdanov as early as 1904: Lenin had fallen out with Nikolai Valentinov, after the latter had introduced him to Ernst Mach's Empiriocriticism, a viewpoint that Bogdanov had been exploring and developing as Empiriomonism . Having worked as co-editor with Plekhanov on Zayra he had come to agree with the latter's rejection of Bogdanov's Empiriomonism . With the defeat of the revolution in mid-1907 and the adoption of a new, highly restrictive election law, the Bolsheviks began debating whether to boycott the new parliament known as the Third Duma . Lenin, Grigory Zinoviev, Lev Kamenev and others argued for participating in the Duma while Alexander Bogdanov, Anatoly Lunacharsky, Mikhail Pokrovsky and others argued that the social democratic faction in the Duma should be recalled . The latter became known as recallists ("otzovists" in Russian). A smaller group within the Bolshevik faction demanded that the RSDLP central committee should give its sometimes unruly Duma faction an ultimatum, demanding complete subordination to all party decisions . This group became known as "ultimatists" and was generally allied with the recallists . </P>

Who were the bolsheviks and why are they important