In 1917 the British government issued the Balfour Declaration, pledging its support for a Jewish national home in Palestine. British troops under General Allenby occupied Palestine during 1917–18, ending 400 years of Turkish rule. The League of Nations made Palestine a British mandate in 1922. (A separate mandate was made for Transjordan, now Jordan, east of the Jordan River.)

About 300,000 Jews emigrated to Palestine between 1922 and 1939, and Jews bought Arab-owned land. The Arab majority feared a Zionist plan to dispossess them and make Palestine a Jewish state. To appease the Arabs, who had revolted during 193637, Britain issued the White Paper of 1939. It virtually cut off Jewish immigration and limited land acquisition by Jews. The Zionists objected, but nevertheless Jewish troops from Palestine supported the British in World War II.

As Nazi destruction of European Jewry proceeded, Zionist leaders pressed for a Jewish state and unrestricted immigration into Palestine. Smuggling of Jewish immigrants became widespread, and there were bloody clashes between Jews and Arabs, and between Jews and the British. The extremist Irgun and Stern groups of Jews conducted a terrorist campaign.