The collectivization of Soviet agriculture was caused in large part by the decision to industrialize the country's economy.  As the process of industrialization occurred, huge numbers of workers moved to various industrial sites.  As this happened, more food was needed from each farmer.  In order to fulfill this need, Stalin decided to collectivize the farms.  He did so because the prosperous farmers (called kulaks) were withholding crops from the market because they could not buy anything with the money they received.  This caused food shortages in Soviet cities.  To combat the shortages, Stalin collectivized agriculture and, in the process, destroyed the kulaksas a class.

Stalin's forced collectivization devastated the Soviet agricultural sector.  This caused widespread famine in which millions are estimated to have died.