The German philosopher, radical economist, and revolutionary leader Karl Marx founded modern scientific socialism. His basic ideas--known as Marxism--form the foundation of socialist and communist movements. Marx spent most of his life in exile, antagonizing Prussian, French, and Belgium governments. He settled in London, where he spent the rest of his life in dire poverty and relative obscurity. His reputation began to spread only after the emergence of the socialist parties in Europe, especially in Germany and France, in the 1870s and 1880s. From then on, Marx's theories continued to be hotly debated in the growing labor and socialist movements everywhere, including Czarist Russia.

By the end of the nineteenth and beginning of the twentieth century, socialist parties had mostly accepted Marxism, particularly the idea of the class struggle and the establishment of a socialist society. Lenin, a lifelong disciple of Marx, organized the Soviet Union as a...