Answer
After Vladimir Lenin died in 1924, a power struggle ensued among his successors. Grigory Zinoviev and Lev Kamenev allied with Joseph Stalin to remove Leon Trotsky from the leadership of the Communist Party of the Soviet Union (CPSU). In 1926, Zinoviev and Kamenev broke with Stalin and allied with Nikolai Bukharin and Alexei Rykov, who favored a more moderate approach to economic policy.