As Caliphs, Ottoman Sultans appointed the Sharif of Mecca, usually selecting a member of the Hashemite family but fostering intra-familial rivalries to prevent a consolidated power base. During World War I, Sultan Mehmed V declared a jihad against the Entente powers. The British sought to align with the Sharif, fearing the Hejaz could threaten their Indian Ocean routes. In 1914, the Sharif, wary of Ottoman intentions to depose him, agreed to support a British-backed Arab Revolt in return for promises of an independent Arab kingdom. After witnessing Ottoman actions against Arab nationalists, he led the Hejaz in successful revolts, except for Medina. In June 1916, Hussein bin Ali declared himself King of Hejaz, with the Entente recognizing his title.^[36]

The British were constrained by a prior agreement granting France control over Syria. Despite this, they established Hashemite-ruled kingdoms in Transjordan, Iraq, and Hejaz. However, border uncertainties, particularly between Hejaz and Transjordan, arose due to the changing Ottoman Hejaz Vilayet boundaries.^[37] King Hussein did not ratify the Treaty of Versailles in 1919 and rejected a 1921 British proposal to accept the Mandate system, especially regarding Palestine and Syria.^[37] Failed treaty negotiations in 1923–24 led the British to withdraw support for Hussein, favoring Ibn Saud, who eventually conquered Hussein's Kingdom.^[38]