Abstract: This article discusses the views of Y. O. Martov and V. M. Chernov regarding the October revolution of 1917 and the key aspects in the life of the Soviet society in the post-October period. The author substantiates the opinion that Russia–USSR in those years lacked the conditions for a victorious socialist construction and provides the views of the above-named political activists which describe the particularities of the seizure and preservation of power by the Bolsheviks. The evaluations of Y. O. Martov and V. M. Chernov on the state’s political structure and economic policy created by the Bolsheviks is also analysed. Furthermore, the policy lines of the Menshevik and SR party programs is indicated in the context of the general political development before and after the October revolution of 1917. The author designates the doctrinal and practical political differences inside the left spectre of political forces in pre-Revolutionary and post-Revolutionary Russia. The basis for this study – the works of Y. O. Martov and V. M. Chernov, which provide rich material for the description of the theoretical heritage of the socialist parties' major leaders.