Rykov joined the Russian Social Democratic Labour Party in 1898, and after it split into Bolshevik and Menshevik factions in 1903, he joined the Bolsheviks, which were led by Vladimir Lenin. He played an active part in the 1905 Russian Revolution. Months prior to the October Revolution of 1917, he became a member of the Petrograd and Moscow Soviets and was elected to the Bolshevik Party Central Committee in July–August of the same year, during the Sixth Congress of the Bolshevik Party. Rykov, a moderate, often came into political conflict with Lenin and more radical Bolsheviks but proved influential when the October Revolution finally overthrew the Russian Provisional Government and as such served many roles in the new government, starting October–November (Old Style) as People's Commissar for Internal Affairs on the first roster of the Council of People's Commissars (Sovnarkom), which was chaired by Lenin.