The Kingdom of Iraq under British Administration or Mandatory Iraq (Arabic: الانتداب البريطاني على العراق‎‎ al-Intidāb al-Brīṭānī ‘Alá al-‘Irāq) was created in 1921 following the 1920 Iraqi Revolt against the proposed British Mandate of Mesopotamia, and enacted via the 1922 Anglo-Iraqi Treaty.

Faisal ibn Husayn, who had been proclaimed King of Syria by a Syrian National Congress in Damascus in March 1920, was ejected by the French in July of the same year. Faisal was then granted by the British the territory of Iraq, to rule it as a kingdom, with the British Royal Air Force (RAF) retaining certain military control, though de facto; the territory remained under British administration until 1932.

The civil government of postwar Iraq was headed originally by the High Commissioner, Sir Percy Cox, and his deputy, Colonel Arnold Wilson. British reprisals after the murder of a British officer in Najaf failed to restore order. The most striking problem facing the British was the growing anger of the nationalists, who continued to fight against the imposition of British authority. British administration had yet to be established in Iraqi Kurdistan.

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