Marx and Engels theorized that capitalist accumulation, industrialization, and the development of the mass worker (who is not only formally but really subordinated to capital, and who could be hardly said to exist in Marx's time) would make revolution. This involved two kinds of statements by Marx: first, the generic version, familiar to all; second the historical version, which has it that the working class is needed to support the bourgeois revolutions against the old orders in Europe, but that working class needs and demands can't be met within the parameters of bourgeois demands and goals, hence a proletarian revolution could or would come about in the course of bourgeois revolutions radicalized by their working class supporters. In both versions, "working class" is the independent variable, so to speak, and "revolution" the dependent variable. (Although of course there is a rich set of dialectics between the two.)
Stalin, primarily, used the Bolshevic revolution to industrialize, that is, proletarianize the peasantry. For him, an industrial proletariat was something to be created or forged. Which happened, just as similar processes were going on in the capitalist world. Forced-draft industrialization, Baran called it, which translates into forced draft proletarianization. The revolution makes the proletariat, in the sociological sense I'm talking about. This in a country (Russia) where only 3 million or so in the work force in 1917 were industrial workers, with 25-26 million peasant families; and where most workers still had ties with the land, many seeing themselves in the city only temporarily. Also where the constituency of the Bolsheviks tended to be the always more militant skilled/craft workers, while the mass worker tended to support the Menshivics. Which from a straight Marx point of view is an anomoly.
For the theme, revolution creates proletariat, in China, if I had felt less frisky (meaning given to perhaps misleading dialectical one-liners), I would have substituted Deng for Mao, in terms of systematic policies to uproot millions from the countryside and make or expand an industrial work force. It's still "revolution creates proletariat," but does a little more justice to the history of Chinese Communism. In terms of the changes in class structure, China after 1979 looks to me alot like Russia from 1928-1938 (first two five year plans).
Fidel and Cuba were different. The workforce in 1958 was 2.1 million. Over 80 percent was wage labor, roughly evenly split between countryside and city. Tiny "peasantry" -- most of the 20,000 poor coffee growers in the Sierras, Fidel's first social base. Here was a revolution where victory came through armed struggle, and where most people were wage workers. Did proletariat create revolution or vice versa? This gets interesting. First there is a revolution in the relations of production, then only much later in the forces of production (bio-medical products, etc.). Fidel's first social base were smallholders and tenants, growing coffee, mainly; then in 1960 the social base widened to include the about 20 percent of the workforce chronically unemployed or underemployed (I did the estimates myself for the Cuban government in 1960). These were the workers who came to hear Fidel's first speeches, and these benefitted most from early revolutionary economic/social policies. The employed productive work force -- well, many wouldn't have it, and went to Miami. More over the years. All kind of job chances opened up for workers migrating to the city and also for the urban unemployed and underemployed. In Cuba, clearly workers didn't make the revolution, nor did the revolution make the working class. But Fidel had (and still has to a degree I guess) the passive consent and at times active participation of the working class. Hence the big difference between Cuba and other revolutions -- there were no social upheavals associated with the process of industrialization/proletarianization, which goes a long way toward explaining the stability of the regime and also the relative ease of establishing Cuban-style socialism. Hoping this clarifies a little. Jim O'Connor