During WW1, with vague promises made by the British of future Arab independence, the Arabs joined the British against the Ottomans. In July 1917 the army of Prince Faysal ibn Husayn (of the Hashimite dynasty) captured Al-'Aqabah (Aqaba), and by October 1918 Amman and Damascus were in Allied hands.

In 1920 at the Conference of San Remo, two mandates were created ; Palestine going to Great Britain, and Syria to France, separating for the first time the area now occupied by Israel and Jordan from that of Syria. Effectively, Ottoman rule was simply replaced by a British or French one.

In November 1920 Abdullah, Faysal's brother, arrived in Ma'an (at that time claimed as part of Hejaz, based on the old Ottoman Vilayet of Hejaz) with 2,000 armed supporters intent on gathering together tribes to attack the French, who had forced Faysal to relinquish his newly founded kingdom in Syria. To defuse the situation -and with a bit of 'horsetrading', the British decided that Abdullah would take over as ruler of what was to become known as Transjordan.

The mandate, gave the British virtually a free hand in administering the territory. By September, the establishment of "a Jewish national home" in Palestine was explicitly excluded from Transjordan, and it was made clear that the area would also be closed to Jewish immigration.

The British recognized on May 25, 1923, Transjordan's independence under the rule of Emir Abdullah, but as outlined in a treaty as well as the constitution in 1928, matters of finance, military, and foreign affairs would remain in the hands of the 'British Resident'.