I mentioned state capitalism in the previous post and linked to a wikipedia entry. This is a link to a more substantial theoretical explanation of what state capitalism is. I draw your attention to a couple of key paragraphs about how the Soviet Union found itself on this path.
Peter Binns: State Capitalism (1986):
"The extreme backwardness of Russia in an age of imperialism forced it to industrialise rapidly. If the revolutions in Germany and elsewhere had succeeded in the early 1920s, plenty of means of production and skilled labour could have flowed into Russia to accomplish this task. But when the perspective changed, from stressing the need to spread the revolution internationally to stressing the building of “socialism” in a single country, as was proposed by Stalin in 1924, the situation was completely reversed.
If industrialisation was to take place in Russia in isolation, this could only be by extracting huge surpluses from the peasantry and by forcing many of these peasants off the land into the mines and steel mills. The Russian bureaucracy could only retain power in so far as it could succeed in this task. It required a vast apparatus of terror to subordinate the consumption of the masses to the need of the Russian state to accumulate.
For a time Stalin tried to avoid this logic. He allied with the right wing of the Bolshevik Party, which spoke of “proceeding towards socialism at a snail’s pace”, without attacks on the peasantry. But this meant that what accumulation there was in the years 1923-28 went into the social services, education, agriculture and food, rather than into heavy industry. Little progress was made in these years towards catching up with the West"