October 1917: Russian workers take power.
November 1917 to summer 1921: The Russian workers' state fights for its life in civil war against counter-revolutionaries, peasant revolts, and 14 foreign armies.
1923 to 1927: Trotsky leads the Left Opposition against the rising Stalinist bureaucracy. Trotskyists and dissidents purged from many Communist Parties outside Russia.
December 1927: Defeat of the Left Opposition in Russia. Trotsky's allies Zinoviev and Kamenev capitulate immediately; Trotskyists sent to exile in remote parts of the USSR.