1. Karl Marx developed the theory of Marxism which viewed history through the lens of class struggle and economic relationships. He believed capitalism exploited workers and would inevitably be overthrown through revolution.
2. Lenin expanded on Marxism, developing the revolutionary vanguard party to organize and lead the proletariat revolution to overthrow capitalism and establish the dictatorship of the proletariat as a transitional stage to communism.
3. Marx argued that under capitalism, workers are alienated and only receive subsistence wages, while the owners reap surplus value from their labor. The class struggle between the bourgeoisie and proletariat would ultimately result in socialist revolution.