In the mid-1930s, the great offensive to build socialism and a new society culminated in ruthless police terror and a massive purging of the Communist Party. In late 1934, Stalin’s number-two man, Sergei Kirov, was mysteriously killed. Stalin — who probably ordered Kirov’s murder — blamed the assassination on “Fascist agents” within the party. He used the incident to launch a reign of terror that purged the Communist Party of supposed traitors and solidified his own control.

Murderous repression picked up steam over the next two years. It culminated in the “great purge” of 1936 to 1938, a series of spectacular public show trials in which false evidence, often gathered using torture, was used to incriminate party administrators and Red Army leaders. In August 1936, sixteen “Old Bolsheviks” — prominent leaders who had been in the party since the Russian Revolution — confessed to all manner of contrived plots against Stalin; all were executed. In 1937, the secret police arrested a mass of lesser party officials and newer members, using torture to extract confessions and precipitating more show trials. In addition to the party faithful, union officials, managers, intellectuals, army officers, and countless ordinary citizens were accused of counter-revolutionary activities. At least 6 million people were arrested, and probably 1 to 2 million of these were executed or never returned from prisons and forced-labor camps.

The purges seriously weakened the Soviet Union in economic, intellectual, and military terms. But they left Stalin in command of a vast new state apparatus, staffed by the 1.5 million new party members enlisted to replace the purge victims. Thus more than half of all Communist Party members in 1941 had joined since the purges, and they experienced rapid social advance. Often the children of workers, they had usually studied in the new technical schools, and they soon proved capable of managing the government and large-scale production. Despite their human costs, the great purges thus brought substantial practical rewards to this new generation of committed Communists. They would serve Stalin effectively until his death in 1953, and they would govern the Soviet Union until the early 1980s.