Russian political leader. A member of the Bolsheviks from 1903, he worked with Vladimir Ilich Lenin in Europe (1909 ?C 14), then returned to Russia, where he was arrested and sent to Siberia. After the Russian Revolution of 1917, he served as head of the Moscow soviet (1919 ?C 25). When Lenin became seriously ill in 1922, Kamenev joined Joseph Stalin and Grigory Y. Zinovyev to form the ruling triumvirate, attacking Leon Trotsky. In 1925 Stalin shifted his attack to Kamenev and Zinovyev, removng Kamenev as Moscow party head. In 1926 Kamenev was expelled from the party after conspiring with Zinovyev and Trotsky against Stalin.