Trotsky was born Lev Bronstein, a Ukrainian Jew, and from his teens was a revolutionary, twice escaping from Siberia after being sent there for his activism against the Czar. He became Lenin's right hand man and was a brilliant organiser and propagandist, largely responsible for creating the Red Army which won the Civil War against the Whites and later was the prime weapon in the defeat of Hitler.
Even a country of Russia's size, however, could not contain him and Stalin, and the latter's liquidation of all opposition drove Trotsky into exile and eventually to assassination in Mexico in 1940 (his assassin, the Catalan Ramon Mercader, served a 20 year jail term and later went to Russia). Stalin made a clean sweep, since Trotsky's two sons, his sister (wife of Kamenev) and his nephews all died in the Terror only his second wife, Natalya, survived.