How did the modern state of Iraq form after World War I?

The modern state of Iraq was formed following World War I by merging the three former Ottoman Empire provinces of Mosul, Baghdad, and Basra.12

Following the war, the League of Nations granted Great Britain a mandate over the region, which was then known as Mesopotamia. This period was marked by significant political unrest, including a widespread revolt in 1920 against British administration. To stabilize the region and address nationalist demands, Britain shifted toward an indirect rule strategy.31

In 1921, Faisal I was installed as king following a plebiscite. The transition to a national regime involved drafting a constitution and establishing a constitutional monarchy with a parliamentary system. Through a series of treaties, including the 1930 Anglo-Iraqi treaty, Britain prepared Iraq for independence. Iraq formally achieved independence and joined the League of Nations in 1932, though it remained subject to British influence for years afterward.142