In 1921, factions were banned in the Russian Communist Party (Bolsheviks). Since 1920 Lenin had become concerned about oppositionist groups within the Communist Party. For example, the Democratic Centralists had been set up in March 1919 and by 1921 Alexander Shlyapnikov had set up the Workers' Opposition. Lenin regarded these as distractions within the party when unity was needed in order to neutralise the major crises of 1921, such as the famines, and Kronstadt Rebellion.