Great Purge

The Great Purge or the Great Terror (), was a purge in the Soviet Union from 1936 to 1938. 
It was a large-scale "repression" of the more wealthy peasants ("kulaks"). Ethnic minorities were murdered. Even members of the Communist Party, government officials, and the Red Army leadership were killed. 
Everyone was watched by the police. Everyone was suspected. People were imprisoned without a fair trial. Executions were common. Historians think the total number of deaths due to Stalinist repression in 1937–38 was between 950,000 to 1.2 million.
The "Kulak Operation" and the targeting of national minorities made up the Great Terror. Together these two actions caused nine-tenths of the death sentences and three-fourths of Gulag prison camp sentences. 
In the Western world, Robert Conquest's 1968 book "The Great Terror" popularized the phrase. Conquest's title was a reminder of the French Revolution time known as the Reign of Terror (French: "la Terreur", "the Terror"; from June to July 1794: "la Grande Terreur", 'the Great Terror').