When did the campaign of political  repression that Mikhail Demichev was arrested during occur?
Great Purge The Great Purge or the Great Terror (Russian: Большо́й терро́р ) was a campaign of political repression in the Soviet Union which occurred from 1936 to 1938. It involved a large-scale purge of the Communist Party and government officials, repression of peasants and the Red Army leadership, widespread police surveillance, suspicion of "saboteurs", "counter-revolutionaries", imprisonment, and arbitrary executions. Mobile gas vans were invented to execute people without trial. In Russian historiography, the period of the most intense purge, 1937–1938, is called Yezhovshchina (Russian: Ежовщина ; literally, "Yezhov phenomenon", commonly translated as "times of Yezhov" or "doings of Yezhov"), after Nikolai Yezhov, the head of the Soviet secret police, the NKVD, who was later killed in the purge. It has been estimated that 600,000 people died at the hands of the Soviet government during the Purge.
Ivan Zhukov Ivan Pavlovich Zhukov (1889 – October 30, 1937) was a Soviet politician. He was a member of the Central Committee elected by the 17th Congress of the All-Union Communist Party (Bolsheviks). He received the Order of Lenin in 1931. During the Great Purge, he was arrested on June 21, 1937, sentenced to death on October 29, 1937 and executed by firing squad the following day. After the death of Joseph Stalin, he was rehabilitated in 1956.