It was founded on 23 August 1921 as the Kingdom of Iraq, following the defeat of the Ottoman Empire in the Mesopotamian campaign of the First World War. Although a League of Nations mandate was awarded to the United Kingdom in 1920, the 1920 Iraqi revolt resulted in the scrapping of the original mandate plan in favour of a formally sovereign Iraqi kingdom, but one that was under effective British administration. The plan was formally established by the Anglo-Iraqi Treaty.