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.
Deportation of the Crimean Tatars The deportation of the Crimean Tatars (Crimean Tatar "Qırımtatar sürgünligi"; Russian "Депортация крымских татар"; Ukrainian "Депортація кримських татар") refers to the ethnic cleansing of Tatars from Crimea on 18 May 1944 carried out by Lavrentiy Beria, chief of the Soviet security and secret police, under the orders of Soviet leader Joseph Stalin. Within a space of three days, the Soviet NKVD deported at least 191,044 Crimean Tatar people in cattle trains—including women, children, and the elderly, as well as Communists and members of the Red Army−several thousands kilometers away to modern-day Uzbekistan. The deportation was ordered by Stalin as collective punishment for the 15,000–20,000 Tatars who had joined the Wehrmacht during the German occupation of Crimea in World War II, even though 25,033 Crimean Tatars had joined the Soviet Red Army during the war.