Deterministic Schema Marxism is a deterministic schema in that according to its doctrine, each subsequent turn of events is a direct result of a specific sequence of causes. According to Marx and Engels in this statement, each stage of history is inevitable and is pushed into the next stage by specific forces, particularly class struggle. Class struggle in a Feudalistic society between the Autocracy, some craftsmen, and infinite numbers of peasants, combined with the onset of the Commercial Revolution in the sixteenth century leads to capitalism. The Industrial revolution that accompanies capitalism causes a new kind of class structure and with it, a new kind of class struggle. The middle class grows in size and wealth while the peasants become the working class and decline in wealth as their depravity increases. The Labor Theory of Value states that the worker can never make it because s/he never receives enough money for the worth of the product.
All of the profit goes to further investment and the proletarian is left overworked and hungry. This class related problem leads to the failure of the capitalist revolution and pushes society into socialism. Socialism is state capitalism. The workers own the companies and the issue of class is avoided it is a classless society. As a deep down moralist, Marx is most interested in the class struggle fueled push into socialism.
He is quite vague about the necessary push from socialism to communism, and is more interested in the capitalism socialism transition. Steps cannot be skipped but can be sped up, so the question would be when will class struggle force society into communism from socialism. Communism according to the manifesto is the withering of the state and the ideal state of existence with much collaboration. Lenin takes the challenge of manipulating time (Marx didnt say when) and bringing communism into play. His was a combination of wanting to grab power for the will of the people and Marxism.