The theory developed by Karl Marx and Friedrich Engels, which became the official doctrine of communism. According to Marxism, the key to how society operated was economics; all other aspects of society, such as politics and religion, were conditioned by the economic system. Under capitalism, society was divided into two classes: the capitalists who owned the means of production and distribution, and the workers, or proletariat, whose labor was exploited by the ruling class. Marx saw history as a dialectical process in which two opposing forces (thesis and antithesis) generate a third, synthesizing force. According to this view, capitalism would eventually break down because of its own contradictions and this would lead to the proletarian revolution and the establishment of the classless society. In the later part of nineteenth century Marxism was adopted by labor and socialist movements in Europe. In the twentieth century Marxist governments came to power in Russia and Eastern Europe, and in varying guises, in Asian countries such as China, North Korea and Vietnam, in Cuba, and in some African countries. In none of these countries did the state eventually wither away and a classless society replace it. On the contrary, Marxist societies were characterized by large and inefficient bureaucracies and had all the trappings of a police state. After the collapse of Soviet and Eastern European communism in 1989 and 1990, Marxism remained a viable system in only a few countries.