In 1939 control over the Haganah was transferred to the MAPAI-dominated Jewish Agency, which was headed by Ben-Gurion. A professional Military General Staff was established and Yaʿakov Dori became the Haganah's first chief of staff. The Haganah ran illegal immigration operations (Aliyah Bet) during and after World War II to circumvent the 1939 White Paper restrictions. At the same time, Britain supported the creation of an elite strike force, the Palmah (Plugot Mahatz, or "shock companies") in May 1941, and Haganah members enlisted in the British Army's Jewish Brigade. When Britain refused to lift the White Paper restrictions after the war, the Haganah and Palmah joined with the Irgun and LEHI to form the Hebrew Resistance Movement (1945 - 1946). The undergrounds coordinated military operations against British targets in Palestine.