This question links to another thread, where we were discussing how it was that Russia and Ukraine had both become major grain exporters. What was a kulak? In the context of the 1920s, it was a peasant who was a competent and therefore successful farmer. Kulaks terrified the Bolsheviks, who imagined that successful peasant farming would turn into capitalist farming (as most Marxists in Russia had long believed) and thereby threaten a capitalist restoration. So in the early 1930s the most capable agriculturalists across the USSR had to be 'liquidated as a class', and in many cases were deported to barren areas of the USSR to scratch a (heavily taxed) living outside of the collective farms. The collectivisation campaign certainly suppressed a possible political threat to Bolshevik rule, but its cost - chronic low agricultural productivity - has only recently been overcome.