New Cambridge History of Islam Vol. 5
The aftermath of the First World War brought a new political order to the entire Middle East, including Arabia. The Ottoman Empire’s collapse ended its role in Arabian affairs while Great Britain reached the peak of its influence. For launching the Arab revolt against the Ottomans, Sharīf Ḥusayn of Mecca received British support to establish the Hashemite kingdom of the Ḥijāz. The resurgent Sa'udī emirate led by 'Abd al-'Azīz ibn Sa'ud had wrested al-Aḥsā' from the Ottomans in 1913 and continued expanding after the war, conquering the Rashīdī emirate of Jabal Shammar in 1921 and the kingdom of the Ḥijāz four years later. In North Yemen, the Ottoman evacuation gave the Zaydī imamate occasion to occupy the coastal plain while Britain retained control over Aden and influence over the southern Yemeni hinterland. Little changed for Gulf coast shaykhdoms in treaty relations, with Great Britain guaranteeing their independence in exchange for conceding London dominance in foreign relations. Beyond the Ottoman sphere, Oman was divided between the coastal area under the British-influenced Ạl Bū Sa'īd sultanate and a reinvigorated Ibāḍī imamate buttressed by tribal forces in the interior.
Commins, David. "Saudi Arabia, Southern Arabia and the Gulf States from the First World War." In New Cambridge History of Islam, edited by Francis Robinson, Vol. 5, 451-80. New York: Cambridge University Press, 2010.