He was a member of the Russian Social-Democratic Labour Party from 1904, and later joined the Bolshevik faction, and worked fulltime, illegally, as a party organiser. Arrested on 24 April (old style) 1908, he spent four years in Vladimir Central Prison, and then was deported to the Irkutsk region. During the October Revolution, he played a major role in bringing Irkutsk under Bolshevik control, and then in creating the Far Eastern Republic. In 1923, he was transferred to Ukraine to supervise organization of the Communist Party committee in Kiev Governorate "(guberniya)" in central Ukraine. In 1925, Postyshev became secretary of the Central Committee of the Communist Party (Bolshevik) of Ukraine, or CP(b)U. In 1926–30 he became a member of the Politburo and Organizational Bureau of Ukraine's Communist Party. At the 15th Congress of the All-Union Communist Party (Bolsheviks), in December 1927, he was elected a member of the Central Committee