The Red Terror was a campaign of mass killings, torture, and systematic oppression conducted by the Bolsheviks after they seized power in Petrograd and Moscow in 1917. Soviet historiography describes the Red Terror as having been officially announced in September 1918 by Yakov Sverdlov and ending about October 1918. However, the term was frequently applied to political repression during the whole period of the Russian Civil War of 1918–1922. The Cheka (the Bolshevik secret police) conducted the mass repressions. Estimates for the total number of people killed in the Red Terror range from 50,000 to 140,000 to over one and a half million.