The most substantial history to date of the famous ‘ultra-left’ tendency within the international Communist movement. The Dutch-German Communist Left, represented by the German KAPD-AAUD, the Dutch KAPN, and the Bulgarian Communist Workers Party, separated from the Communist International in 1921, and famously attracted the ire of Lenin, who wrote his Left Wing Communism in response. Drawing on a wide breadth of first hand material, this volume examines the history, ideas, and legacy of this tendency.