With Rosa Luxemburg, Leo Jogiches was the founder of the revolutionary Social Democracy of the Kingdom of Poland, in 1893. He was the Party’s main practical leader and also the principal organiser of the Spartakist League, the largest revolutionary group in Germany during the First World War, and then the Communist Party of Germany. Jogiches and Luxemburg, as leaders of Polish social democracy, were vehement opponents of Polish nationalism. Like Lenin, he saw the need for a centralised and disciplined, revolutionary party, with roots in the working class, if workers were ever to take and hold political power.