A leader of the Ha-Shomer Ha-Tzair organization, one of the founders and commanders of the Jewish Combat Organization (ŻOB), a heroic liaison between ŻOB and the Home Army (AK) on the "Aryan side," participant in the Warsaw Ghetto Uprising. A poet.
Talented scholar and social activist, founder of JIKOR (Jewish Cultural Organization in the Ghetto), collaborator of Oneg Shabbat, murdered on "Bloody Friday" in 1942.