The British Mandate for Palestine (valid 29 September 1923 - 15 May 1948), also known as the Mandate for Palestine or the Palestine Mandate, was a "Class A" League of Nations mandate for the territories of Palestine, in which the Balfour Declaration's "national home for the Jewish people" was to be established, and Transjordan, a separate Arab Emirate, both of which were conceded by the Ottoman Empire following World War I.
The document was based on the principles contained in Article 22 of the Covenant of the League of Nations of 28 June 1919 and of the San Remo Resolution of 25 April 1920, which embodied decisions made after World War I at the San Remo conference, where the Supreme Council of the Principal Allied Powers was reconvened. The objective of the system of Class A mandates was to administer parts of the defunct Ottoman Empire, which had been in control of the Middle East since the 16th century, "until such time as they are able to stand alone". The approximate northern border with the French Mandate was agreed upon in the Paulet–Newcombe Agreement of 23 December 1920.
Transjordan was included in the mandate following a March 1921 conference at which it was agreed that Abdullah bin Hussein would administer the territory under the auspices of the Palestine Mandate. After the war it had been administered from Damascus by a joint Arab-British military administration, headed by Abdullah's younger brother Faisal, who was subsequently proclaimed King. Transjordan became a no man's land after the French removed Faisal in the July 1920 Battle of Maysalun; during which period the British chose to avoid any definite connection with Palestine. This was given legal form on 21 March 1921 when the British introduced Article 25 into the Palestine Mandate, which included Transjordan within the scope and allowed the Mandatory there "to postpone or withhold application of such provisions of this mandate as he may consider inapplicable to the existing local conditions." On 16 September 1922, Article 25 was implemented via the Trans-Jordan memorandum, which established a separate "Administration of Trans-Jordan" for the application of the Mandate, under the general supervision of Great Britain. Transjordan became largely autonomous under British tutelage according to an agreement of 20 February 1928, and fully independent under a treaty with Britain of 22 March 1946.
On 29 November 1947, the United Nations Partition Plan for Palestine was passed, envisaging the creation of separate Jewish and Arab states operating under economic union with Jerusalem being transferred to UN trusteeship. Two weeks later, Colonial Secretary Arthur Creech Jones announced that the British Mandate would terminate on 15 May 1948. On the last day of the Mandate, the creation of the State of Israel was proclaimed, and the 1948 Arab–Israeli War began.
On 2 November 1917, during World War I, the British government issued the Balfour Declaration, a public statement announcing support for the establishment of a "national home for the Jewish people" in Palestine, then an Ottoman region with a minority Jewish population (around 3–5% of the total).
Immediately following their declaration of war on the Ottoman Empire in November 1914, the British War Cabinet began to consider the future of Palestine. By late 1917, in the lead up to the Balfour Declaration, the wider war had reached a stalemate, with two of Britain's allies not fully engaged: the United States had yet to suffer a casualty, and the Russians were in the midst of a revolution. A stalemate in southern Palestine was broken by the Battle of Beersheba on 31 October 1917. The release of the Balfour Declaration was authorised by 31 October; the preceding Cabinet discussion had referenced perceived propaganda benefits amongst the worldwide Jewish community for the Allied war effort.