Biography of Berl Katznelson (1987-1944), leader and ideologist of the labor movement in Zionism, compiled by historian, professor at Tel Aviv University Anita Shapira. Written in the condensed language of an encyclopedic article, the book details the political activities of Berle Katznelson, specifically dwelling on its historical context. Berl Katznelson is one of the most prominent, iconic figures of socialist Zionism; leader and authoritative ideologist of the Jewish labor movement in Palestine and beyond. Berle Katznelson participated in the creation of the Histadrut and more than anyone determined the nature and scope of its activities. He was the creator and first editor-in-chief of the Histadrut organ, the Davar newspaper. He initiated the creation of the Ha-Poalim Bank (Workers' Bank). He was a board member of the World Zionist Organization and a member of the directorate of the Jewish National Fund. He made a great contribution to the unification of workers' parties and the creation of a new party from them - Mapai (the predecessor of Avoda).