 In 1896 he joined the Social Democracy of the Kingdom of Poland (SDKP - later the Social Democracy of the Kingdom of Poland and Lithuania (SDKPiL)) led by Rosa Luxemburg and her lover, Leo Jogiches.He moved to Germany in 1901 and studied in rapid succession at Berlin, Heidelberg, and Zurich universities.From 1902, he was a professional revolutionary, normally based in Cracow, under Austrian rule, organising the transport of illegal literature across the Russian border.