Iraq is a veritable treasure house of antiquities, and recent archaeological excavations have greatly expanded the knowledge of ancient history. Prior to the Arab conquest in the 7th cent. AD, Iraq had been the site of a number of flourishing civilizations, including the Sumer, which developed one of the earliest known writing systems, Akkad, Babylonia, and Assyria. The capital of the Abbasid caliphate was established at Baghdad in the 8th cent. and the city became a famous center for learning and the arts.
Despite fierce resistance, Mesopotamia fell to the Ottoman Turks in the 16th cent. and passed under direct Ottoman administration in the 19th cent. (see Ottoman Empire, when it came to constitute the three Turkish provinces of Basra, Baghdad, and Mosul. At this time the area became of great interest to the European powers, especially the Germans, who wanted to extend the Berlin-Baghdad railroad all the way to the port of Kuwait.
In World War I the British invaded Iraq in their war against the Ottoman Empire; Britain declared then that it intended to return to Iraq some control of its own affairs. Nationalist elements, impatient over delay in gaining independence, revolted in 1920 but were suppressed by the British. Late that year the Treaty of Svres established Iraq as a mandate of the League of Nations under British administration, and in 1921 the country was made a kingdom headed by Faisal I. With strong reluctance an elected Iraqi assembly agreed in 1924 to a treaty with Great Britain providing for the maintenance of British military bases and for a British right of veto over legislation. By 1926 an Iraqi parliament and administration were governing the country. The treaty of 1930 provided for a 25-year alliance with Britain. The British mandate was terminated in 1932, and Iraq was admitted to the League of Nations.