The Mandate for Palestine came into effect, officially creating the protectorates of Mandatory Palestine under British administration and Transjordan as a separate emirate under King Abdullah I.

The Mandate for Palestine was a League of Nations mandate for British administration of the territories of Palestine and Transjordan – which had been part of the Ottoman Empire for four centuries – following the defeat of the Ottoman Empire in World War I. Under the mandate, Britain assumed obligations both to the inhabitants of Palestine and to the establishment of a Jewish national home, as set out in the British government's 1917 Balfour Declaration. The mandate was assigned to Britain by the San Remo conference in April 1920, after France's concession in the 1918 Clemenceau–Lloyd George Agreement of the previously agreed "international administration" of Palestine under the Sykes–Picot Agreement. Transjordan was added to the mandate after the Arab Kingdom in Damascus was toppled by the French in the Franco-Syrian War. Civil administration began in Palestine and Transjordan in July 1920 and April 1921, respectively, and the mandate was in force from 29 September 1923 to 15 May 1948 and to 25 May 1946 respectively.