Born in the Ukraine, Hayim Arlosoroff was taken by his parents to Germany in 1905 following a pogrom there. He went on to become a noted leader of the Labor Zionist movement in Palestine. While still in Germany, Arlosoroff had already become very active in Zionist affairs. In 1918, he co-founded Ha-Po'el ha-Tza'ir, a party which attracted many intellectuals of the time. Later, when Ha-Po'el ha-Tza'ir merged with Tze'irei Zion, Arlosoroff emerged as one of the leaders of the new "Histadrut" (Union).
After his arrival in Palestine in 1921, Arlosoroff represented his party in the Histadrut. Soon after, he went back to Germany in order to complete his doctorate and returned to Palestine in 1924. In 1926 he was chosen to represent the yishuv at the League of Nations in Geneva.
Arlosoroff was well-known for his particular ideological convictions. He vehemently disagreed with specific policies of his party and viewed prospects for unification of the Histadrut and Ahdut ha-Avoda (another Zionist-socialist party) with skepticism. Despite his objections, Arlosoroff's party merged with Ahdut ha-Avoda, leading to the creation of Mapai. Arlosoroff's voice was an important one amongst Mapai leaders.
Along with Chaim Weizmann, Arlosoroff supported the expansion of the Jewish Agency to include non-Zionists. He served on the expanded Agency's Administrative Committee, and continued to support other of Weizmann's policies. These policies included cooperation with the British government and understanding of the Arab position.
With the advent of Nazi Germany, Arlosoroff became a key player in the Ha'avara program, allowing the Jews of Germany to transfer some of their belongings to Palestine. He served as a link between German authorities and the yishuv, facilitating Jewish immigration and settlement.
Hayim Arlosoroff was murdered in June, 1933, while walking on the Tel Aviv beach with his wife Sima. The identity of his attackers is the subject of much controversy, unsolved to this day.
Source: The Jewish Agency for Israel and The World Zionist Organization.