In What Is to Be Done? Lenin laid down a scheme for an underground party aiming to overthrow the Russian absolute monarchy.
Earlier Marxists had written little about how parties should be organised, and here Lenin's scheme for the Russian political underground involved a ruthlessly centralised organisation of dedicated activists. What is To Be Done? had an immense and immediate influence and attracted fierce controversy, and it almost certainly helped to bring about the crucial split between Bolsheviks and Mensheviks that subsequently altered the course of world history. And, despite its origin in forgotten controversies, it soon became established as one of the definitive statements of Marxism-Leninism, the most influential ideology of the twentieth century.