Soviet leader Josef Stalin arguably set the bar on 20th-century totalitarianism. But it took him years to gain full control after the death of Bolshevik icon Vladimir Lenin.
Stalin and his cronies set up show trials of the late 1930s to convict and execute potential rivals often with trumped-up charges and forced confessions.
Nikolai Bukharin was shot for spying. Two other Communist notables Lev Kamenev and Grigory Zinoviev were executed as alleged conspirators of Leon Trotsky, Stalin's last and best-known rival.
Trotsky was assassinated by an icepick to the head while he was in exile in Mexico in 1940. Stalin died in power 13 years later.
