If there is one thing which separates the revisionist sheep from the Leninist goats it is the question of power: what is it, how do you take it, how do you defend it and how do you hold on to it? If we consider Marx to be the theoretician of revolution, then it is Lenin who sought to marry theory with practice. The debate as to whether there is a continuity between Marx, Lenin and Stalin, that one leads ineluctably to the other and from there straight to the cellars of the Lubyanka, is one which has raged since Rosa Luxemburg criticised Lenin and which will, probably, continue for centuries to come.
There are basically three camps: first, paradoxically, an alliance of the Stalinist diehards and anti-communists who posit a direct and logical connection between Marx and Stalin, for better or for worse; second, those who see a distinct break between Lenin and Stalin (largely Trotskyists) and third; those who see a break between Marx and Lenin and who admire the former for his analytical skills but oppose the latter's dictatorial measures. We might call this third group the platonic Bolshevists who would like to live in a different world, but are not quite sure that they like the measures taken to get there.
The emergence of the idea of the dictatorship of the proletariat comes from the fact that in the bourgeois epoch history had both speeded up and wised up. Marx pointed out that in the transition between the previous epochs he had outlined, from ur-communism to the ancient mode, from there into feudalism and on to bourgeois capitalism, there is an acceleration of the process of transformation as well as a growing political consciousness. The early historical stages are slow, almost organic transitions taking many centuries. Where does one system slide into the next and how does it happen? Marx, and in particular Engels, developed the idea of the dialectic of quantity into quality, small incremental changes in a prevailing system which at some point add up to more than the sum of their parts and contribute to a full transition or a sudden Hegelian leap, as Lenin put it, to something new.
In 19th-century Europe this was increasingly the case. The workers in the major industrial countries in Europe did combine into unions and political movements and parties which were determined to improve their lot. The question was how this growing pressure could be either combated or accommodated. Under Bismarck for example, it became clear that the proletariat was a growing threat and, after the banning of the socialist party, social measures were brought in by the mid-1880s to ameliorate the situation for workers in a system that was then called a form of "state socialism".
http://www.guardian.co.uk/commentisfree/2011/may/02/karl-marx-power-dictatorship-proletariat