When the Ottoman Empire collapsed in 1918, the lands between the Tigris and Euphrates did not slide neatly into peace. Britain stayed on as the occupying power and, in 1920, gained a League of Nations mandate to build a new state out of the former Ottoman vilayets of Basra, Baghdad, and Mosul. The result was a hybrid order: a Hashemite monarchy headed by Faisal I and an Iraqi cabinet, but with British advisors, bases, and treaty rights embedded at the core of security, foreign affairs, and (increasingly) oil. The settlement reflected real Iraqi aspirations for self-rule—voiced by urban notables, tribal leaders, and clerics—but also British strategic priorities (India route, the Gulf, airfields) and the economic promise of Kirkuk crude coming into sharper view after 1927.
A revolt that forced a rethink (1918–1921)
Iraqi politics hardened during the war years and boiled over into the Great Iraqi Revolt of 1920, a cross-sectarian uprising that spread from the mid-Euphrates into central and northern districts. The rising was crushed by a combination of punitive ground operations and a new British doctrine of "air control," but it changed policy in London: direct rule was too costly, so Britain shifted to "indirect" rule via a Faisal monarchy under mandate. That compromise—popular sovereignty ring-fenced by imperial guarantees—would define the decade.
Borders, bases, and the mandate state (1920s)
Two dossiers shaped early statehood. First, the Mosul Question: after prolonged wrangling, the League of Nations recommended Mosul remain with Iraq; the Treaty of Ankara (1926) fixed the frontier and gave Turkey a royalty share from Mosul oil—an early sign that hydrocarbons, not just history, would determine borders. Second, security: Britain consolidated RAF Iraq Command with major air bases at Habbaniya and Shaibah, backed by locally recruited Iraq (Assyrian) Levies. Air power and Levies were sold as economical tools to hold the periphery while the national army found its feet; they also entrenched resentment, particularly when used against restive regions.
Society and power: who spoke for "Iraq"?
The mandate assembled a political elite—Sunni Arab notables in Baghdad and Mosul, Shiʿa clerics and tribal leaders in the mid-Euphrates, Kurdish chiefs in the north—into a new parliamentary order. But representation was uneven: Shiʿa and Kurdish grievances persisted, and the state alternated between bargaining and coercion. That pattern continued even after formal independence. In 1935–1936, the government crushed Shiʿa tribal uprisings in the mid-Euphrates; two years earlier, the Simele massacre (1933) had seen Assyrian civilians killed amid tensions over the Levies and minority status—events that left lasting scars on the new nation's social contract.
From mandate to "independence" (1930–1932)
The Anglo-Iraqi Treaty of 1930 promised a path out of the mandate and into the League of Nations (achieved in 1932), but it also locked in British privileges: rights of troop transit and the maintenance of air bases in peacetime. In effect, sovereignty arrived by treaty—with strings. The arrangement reflected Baghdad's desire for recognition and London's insistence on strategic depth as oil exports ramped through the Iraq Petroleum Company and the Kirkuk–Haifa/Tripoli pipeline reached the Mediterranean by 1934–1935.
Wikipedia: Anglo-Iraqi Treaty (1930) • Encyclopedia Britannica
Coups, currents, and a region in motion (mid-late 1930s)
Independence did not settle politics. In 1936, General Bakr Sidqi staged the Arab world's first modern military coup, briefly inaugurating an era in which the army became arbiter of cabinet politics before Sidqi himself was assassinated the next year. In the same years, the state oscillated between centralizing reforms and regional unrest, while managing Kurdish, Assyrian, and Shiʿa demands with a mix of patronage and force. Oil revenues grew, infrastructure expanded, and Iraqi diplomats sought a wider Arab role, yet the security architecture still rested on British treaty rights and RAF bases—fault lines that would crack open again in 1941.
What held—and what didn't
By 1939, Iraq was formally independent, increasingly urban, and tied into global oil markets. But it was also a state born of a revolt and a mandate, its institutions shaped by bargains with empire: borders decided in Geneva, sovereignty mediated by airfields, and domestic order sometimes enforced from the sky. Those contradictions yielded a politics that was vibrant and unstable at once—setting the stage for the short, sharp Anglo-Iraqi War in 1941 and for Iraq's turbulent 20th century to come.
Sources & further reading
- Britannica on British occupation/mandatory regime and the road to independence
- League of Nations & treaties: Mosul Question and Treaty of Ankara (1926); Anglo-Iraqi Treaty (1930).
- Security architecture: RAF Iraq Command, RAF Habbaniya, and the Iraq (Assyrian) Levies.
- Society & conflict: the 1920 Revolt, the Simele massacre (1933), and the 1935–36 mid-Euphrates uprisings.
- Oil economy & pipelines: Kirkuk strike (1927) and the Kirkuk–Haifa/Tripoli pipeline.