The Treaty of Ankara (1926): When Kurdistan Was Sold for Oil

Jamal Latif
May 24
7 min read

Map of the Turkey-Iraq border through Kurdish territories as fixed by the Treaty of Ankara 1926

Introduction

On 5 June 1926, Turkey, Britain, and Mandatory Iraq signed the Treaty of Ankara — also known as the Frontier Treaty of 1926 — finally resolving the ‘Mosul Question’ that had been left open at Lausanne three years earlier. Turkey reluctantly accepted that the oil-rich Mosul vilayet, home to hundreds of thousands of Kurds, would belong to Iraq. In exchange, Turkey received 10 percent of the Iraqi government’s oil royalty payments for twenty-five years. The Kurdish homeland was sold — literally — for a share of petroleum revenue.

For the Kurdish people, the Treaty of Ankara was the final nail in the coffin of any hope that the post-World War I settlement would deliver justice. The Treaty of Sèvres (1920) had promised Kurdish autonomy and independence. The Treaty of Lausanne (1923) had erased those promises. Now the Treaty of Ankara determined the precise border that would divide the Kurds of Turkey from the Kurds of Iraq — a line drawn through the Zagros Mountains that, over a century later, remains one of the most contested and militarised borders in the Middle East.

What Was the Treaty of Ankara?

Oil Over Kurdish Rights

Timeline

Legacy and Significance

FAQ

References

What Was the Treaty of Ankara (1926)?

The Treaty of Ankara (also known as the Frontier Treaty of 1926) was signed on 5 June 1926 by Turkey, the United Kingdom, and Mandatory Iraq. It resolved the Mosul Question — the dispute over whether the oil-rich Mosul vilayet would belong to Turkey or Iraq — that had been left unresolved by the Treaty of Lausanne (1923). The treaty awarded Mosul to Iraq and established the Turkey-Iraq border along the ‘Brussels Line’ that had been provisionally adopted by the League of Nations on 29 October 1924.

The Mosul vilayet had a population of approximately 300,000 Kurds, 170,000 Arabs, and 40,000 Turks on the eve of World War I, as well as communities of Assyrian Christians and Yazidis. Despite its overwhelmingly Kurdish population, the vilayet’s fate was decided by three parties — Turkey, Britain, and the Arab-led Iraqi government — none of whom represented Kurdish interests. The Kurds were, once again, objects of international diplomacy rather than participants in it.

Key Takeaways

• The Treaty of Ankara awarded the Kurdish-majority Mosul vilayet to Iraq — Turkey relinquished its claim to the region in exchange for 10% of Iraqi oil royalties for twenty-five years.

• No Kurdish representative participated in the negotiations — the fate of hundreds of thousands of Kurds was decided by Turkey, Britain, and Iraq without Kurdish input.

• The treaty granted Turkey the right to engage militarily in the border region if it became destabilised — a provision that has been invoked repeatedly to justify Turkish military incursions into Iraqi Kurdistan.

• Oil was the decisive factor — Britain needed Mosul’s oil for its strategic interests, and the Turkish Petroleum Company (later the Iraq Petroleum Company) had secured a 75-year concession just months before the treaty was signed.

Quick Facts

Treaty: Treaty of Ankara (Frontier Treaty of 1926) Date: 5 June 1926 Signatories: Turkey (Tevfik Rüştü Aras), United Kingdom (Ronald Lindsay), Iraq (Nuri al-Said) Type: Border and frontier treaty Key Provision for Kurds: Mosul vilayet (Kurdish-majority) awarded to Iraq; Turkey receives 10% of Iraqi oil royalties for 25 years Border: ‘Brussels Line’ (adopted 29 October 1924) became the Turkey-Iraq border Military Provision: Turkey granted right to military action in border region if destabilised Oil: Turkish Petroleum Company held 75-year concession (signed March 1925); oil discovered near Kirkuk in 1927 Significance: Finalised the division of northern and southern Kurdistan between Turkey and Iraq

Historical Context: The Mosul Question

The Mosul vilayet had been part of the Ottoman Empire until British forces occupied it in late 1918. The Treaty of Sèvres (1920) had envisaged the potential incorporation of the vilayet into an independent Kurdistan. But Sèvres was never implemented, and the Treaty of Lausanne (1923) left the Mosul question unresolved, providing that if Turkey and Britain could not reach agreement within nine months, the issue would be referred to the League of Nations.

Turkey repeatedly claimed sovereignty over Mosul from 1923 to 1926, citing geographic, demographic, and ethnic arguments. Britain insisted on retaining Mosul within Iraq, driven primarily by oil interests — the Turkish Petroleum Company had been granted a 75-year concession to exploit Mosul’s oil in March 1925. The League of Nations appointed an investigative commission that recommended Iraq should retain Mosul, and Turkey reluctantly accepted the decision by signing the Treaty of Ankara.

The Treaty Terms: A Border Through Kurdistan

The treaty’s key provisions were straightforward: Mosul Province would belong to Iraq. The ‘Brussels Line’ — a provisional border adopted by the League of Nations in October 1924 — would serve as the permanent frontier between Turkey and Iraq. Turkey would receive 10% of the Iraqi government’s oil royalty payments for twenty-five years as compensation for relinquishing its claim. Turkey also retained the right to engage in military conflict in the border region in the event of destabilisation.

The border drawn by the treaty ran through some of the most rugged terrain in the Zagros Mountains — directly through the heart of Kurdish-inhabited territory. Kurdish communities that had maintained connections across this region for centuries were now permanently separated by an international border. Northern Kurds became citizens of Turkey, where their identity would be denied. Southern Kurds became subjects of Mandatory Iraq, where their autonomy promises would be broken. The border has remained ‘extremely rugged and porous’ ever since — practically uncontrollable, a permanent source of conflict.

Oil Over Kurdish Rights: The Real Currency of the Treaty

The Treaty of Ankara was, at its core, an oil deal. Britain needed Mosul’s oil to fuel its navy and its global empire. The Turkish Petroleum Company had secured its 75-year concession in March 1925 — just over a year before the treaty was signed. Oil was discovered near Kirkuk in 1927, and the first significant commercial exploitation began in 1934 with the opening of the Kirkuk-Haifa oil pipeline.

Turkey’s acceptance of the treaty was purchased with oil money — 10% of royalties for twenty-five years, payments that continued regularly from 1931 to 1952. The Kurdish people of Mosul were not consulted about whether they wanted to be part of Iraq, or Turkey, or an independent Kurdistan. Their homeland was assigned to the state that served British oil interests, and the price was negotiated in petroleum revenues. The League of Nations’ investigative commission had noted the overwhelming Kurdish majority in the region, but Kurdish self-determination was never seriously considered. Oil trumped Kurdish rights.

Timeline of Key Events

1918 — British forces occupy the Mosul vilayet.

1920 — Treaty of Sèvres envisages Mosul Kurds joining an independent Kurdistan; never implemented.

July 1923 — Treaty of Lausanne leaves the Mosul question unresolved.

October 1924 — League of Nations adopts the ‘Brussels Line’ as the provisional Turkey-Iraq border.

March 1925 — Turkish Petroleum Company secures 75-year oil concession in Mosul.

December 1925 — League of Nations awards Mosul to Iraq.

5 June 1926 — Treaty of Ankara signed; Turkey accepts Mosul’s inclusion in Iraq for 10% oil royalties.

1927 — Oil discovered near Kirkuk; commercial exploitation begins in 1934.

Legacy and Significance for Kurdish History

The Treaty of Ankara is significant because it finalised the division of northern Kurdistan (Turkey) from southern Kurdistan (Iraq). Where the Treaty of Lausanne had established Turkey’s borders and erased Kurdistan from international law, the Treaty of Ankara determined the precise line that would separate the Kurds of Bakur (North Kurdistan) from the Kurds of Başûr (South Kurdistan). This border has remained one of the most contested and militarised frontiers in the Middle East.

The treaty’s provision granting Turkey the right to military action in the border region has had enduring and devastating consequences. Turkey has invoked this right repeatedly to justify cross-border military operations into Iraqi Kurdistan — from the pursuit of Kurdish fighters in the 1990s to ongoing Turkish military operations against the PKK in the mountains of southern Kurdistan today. The provision transformed the Turkey-Iraq border from a line on a map into a permanent military frontier through the Kurdish homeland.

The Kurdish saying ‘no friends but the mountains’ was born from this era. The Kurds became concentrated minorities within new centralised states that, in practice, followed policies of identity suppression, forced assimilation, and military repression throughout the twentieth century. Pressured and at times outright attacked by these regimes, the Kurds found sanctuary only in the rugged peaks and ravines of the Zagros range. The Treaty of Ankara, by fixing the border through those very mountains, ensured that even the mountains would be divided.

Frequently Asked Questions

What was the Treaty of Ankara (1926)?

A frontier treaty signed on 5 June 1926 by Turkey, Britain, and Iraq that resolved the Mosul Question. Turkey accepted that the Kurdish-majority Mosul vilayet would belong to Iraq in exchange for 10% of Iraqi oil royalties for twenty-five years. The treaty established the permanent Turkey-Iraq border through Kurdish territory.

Why did Turkey give up Mosul?

Turkey was unable to challenge the League of Nations decision and British military power in the region. It accepted Mosul’s inclusion in Iraq in exchange for 10% of oil royalties, a right to military action in the border zone, and normalised relations with Britain. The decision was driven by oil interests and great-power politics, not Kurdish welfare.

How does this treaty affect Kurdish-Turkish relations today?

The treaty’s provision granting Turkey military rights in the border region has been invoked to justify repeated Turkish military incursions into Iraqi Kurdistan, including ongoing operations against the PKK. The Turkey-Iraq border remains one of the most militarised frontiers in the Middle East, cutting through Kurdish communities that maintain connections across it.