What historical role did Marx assign to the proletariat?

According to Marx, the proletariat would revolt against and overthrow the owners of the means of production , i.e. the bourgeoisie. The victory of the proletariat would mean that, for the first time in history, one group of people would not be oppressing an other. This new society would be called Communism. The new society would indirectly transition to Communism via a socialist stage, where class distinctions remained in existence and power while the means of the production, being socialised, would break down the existing social distinctions in society.