Revolutionary, theorist, and founder of the Soviet state. Vladimir Ilyich Ulyanov transformed Marxism from a critical theory of capitalism into the operating doctrine of a party that, in 1917, seized state power in the world's largest country. Whatever one's verdict on that outcome, no other 20th-century figure reshaped political history more decisively.
Lenin's theoretical contributions were driven by practical problems orthodox Marxism could not solve. What Is to Be Done? (1902) argued that workers, left to themselves, will develop only "trade-union consciousness" — a bargaining relationship with capital — not revolutionary consciousness; the latter must be brought to them by a disciplined party of professional revolutionaries. This vanguard thesis became the foundation of Bolshevik organization and of every Leninist party since. Imperialism, the Highest Stage of Capitalism (1916) argued that mature capitalism had evaded Marx's predicted crises by exporting exploitation abroad — the First World War, on this reading, was a war among imperialist powers fighting over colonial spoils, and the revolution would now likely break out first at the "weak link" of the imperial chain rather than in the industrial core.
The State and Revolution (1917), written in hiding just before the October coup, insisted that the proletariat could not simply take over the existing bourgeois state but would have to smash it and replace it with a "dictatorship of the proletariat" — transitional, participatory, withering away over time. The actuality of Soviet power diverged rapidly and catastrophically from the text's sketches. Lenin's last writings, shaped by a series of strokes, show a dying man increasingly alarmed by the bureaucratic apparatus he had helped build and by the ascent of Stalin.