Polish Socialist Party
Born on 26 August 1883 in a family of Ukrainian origins in Tarnopol, he studied law in Lwów University but dropped his studies to become a full-time political activist. He joined the Polish Socialist Party around 1904 and was the cofounder, together with Józef Piłsudski, of Polish Socialist Party - Revolutionary Faction ("Polska Partia Socjalistyczna - Frakcja Rewolucyjna") in 1905.