Ben-Zvi is born in Ukraine, making aliyah in 1907 and becoming one of the leaders of the Poalei Zion (Workers of Zion) Party and early labor movements in the yishuv. He is active in Jewish self-defense in the yishuv and is one of the founders of both Bar Giora and Hashomer, groups of defenders and guards for Jewish settlements. He holds leadership positions in many of the early political and social organizations including serving as Chairman of the Va’ad Leumi (the Yishuv Executive Committee) in 1931 and as its President in 1945. A delegate to many Zionist Congresses, he goes on public missions to countries of the Middle East including Egypt, Syria, Lebanon, Iraq and Persia (Iran) in 1935 and visits most European countries to promote the Yishuv and Zionist causes. He is a signer of the Declaration of Independence in May 1948.