According to the political theory of Marxism–Leninism of the early 20th century, the kulaks were class enemies of the poorer peasants. Vladimir Lenin described them as "bloodsuckers, vampires, plunderers of the people and profiteers, who fatten on famine". Marxism–Leninism had intended a revolution to liberate poor peasants and farm laborers alongside the proletariat (urban and industrial workers). In addition, the planned economy of Soviet Bolshevism required the collectivisation of farms and land to allow industrialisation or conversion to large-scale agricultural production. In practice, government officials violently seized kulak farms and killed resisters while others were deported to labor camps.
According to the Soviet terminology, the peasants were divided into three broad categories: bednyak, or poor peasants; serednyak, or mid-income peasants; and kulak, the higher-income farmers who had larger farms than most Russian peasants. In addition, they had a category of batrak, landless seasonal agriculture workers for hire.
The Stolypin reform created a new class of landowners by allowing peasants to acquire plots of land for credit from the large estate owners. They were to repay the credit (a kind of mortgage loan) from their farm work. By 1912, 16% of peasants (up from 11% in 1903) had relatively large endowments of over 8 acres (3.2 ha) per male family member (a threshold used in statistics to distinguish between middle-class and prosperous farmers, i.e. the kulaks). At that time, an average farmer's family had 6 to 10 children. The number of such farmers amounted to 20% of all rural courts while their production level was reaching 50% of marketable grain.
After the Russian Revolution of 1917, the Bolsheviks considered only batraks and bednyaks as true allies of the Soviets and proletariat. Serednyak were considered unreliable, "hesitating" allies; and kulak were identified as class enemies because they owned land (later this was expanded to include those who owned livestock), but a middle peasant who did not hire labor and was little engaged in trade "might yet (if he had a large family) hold three cows and two horses". There were other measures that indicated the kulaks as not being especially prosperous. The average value of goods confiscated from kulaks during the policy of "dekulakization" (раскулачивание) at the beginning of the 1930s was only $90–$210 (170–400 rubles) per household. Both peasants and Soviet officials were often uncertain as to what constituted a kulak. They often used the term to label anyone who had more property than was considered "normal", according to subjective criteria, and personal rivalries played a part in the classification of enemies. Historian Robert Conquest argues:
The land of the landlords had been spontaneously seized by the peasantry in 1917–18. A small class of richer peasants with around fifty to eighty acres had then been expropriated by the Bolsheviks. Thereafter a Marxist conception of class struggle led to an almost totally imaginary class categorization being inflicted in the villages, where peasants with a couple of cows or five or six acres more than their neighbors were now being labeled "kulaks," and a class war against them declared.