Treaty of Lausanne
The 1923 settlement that tore up the plan to partition Turkey, fixed its borders, legalized mass population transfer, and erased Kurdistan.
The Treaty of Lausanne is the only peace settlement from the First World War that a defeated power rewrote by winning a subsequent war, and it is the reason the Republic of Turkey exists in its current shape. Signed on 24 July 1923, it replaced the Treaty of Sevres of 1920, which had partitioned Anatolia among the victors. Understanding the pair is the fastest way to understand why Turkey, Greece, and the Kurds behave the way they do about their borders a century later.
What Sevres would have done
Sevres was the harshest of the postwar treaties. It stripped the Ottoman Empire of its Arab provinces, which was expected, and then went considerably further inside Anatolia itself. Greece received Izmir and its hinterland with a referendum promised later. Italy and France got zones of influence in the south. The Straits were internationalized under Allied control. An independent Armenia was recognized in the east, and an autonomous Kurdish region was outlined with a path to independence. The capitulations, the old privileges exempting foreigners from Ottoman law and tariffs, were confirmed and extended.
The sultan's government signed it in August 1920. The Turkish national movement under Mustafa Kemal did not, and it had the army. The Turkish War of Independence that followed drove the Armenians back in the east, forced the French out of the south, and in September 1922 pushed the Greek army into the sea at Izmir. Sevres was dead before it was ever ratified, killed on the battlefield.
What Lausanne did instead
The conference at Lausanne pitted Ismet Pasha, later Ismet Inonu, against Lord Curzon, and the Turkish delegation arrived negotiating from victory. The result reversed nearly everything.
Turkey's borders in Anatolia and eastern Thrace were recognized essentially as its army had established them, and they have barely moved since. Article 28 abolished the capitulations completely, restoring full Turkish sovereignty over its own law and tariffs. No reparations of consequence were imposed. There was no independent Armenia and no Kurdistan: the Kurdish provisions of Sevres simply vanished, and Kurds were divided among Turkey, Iraq, Syria, and Iran with no recognized national claim anywhere. The Straits were demilitarized under an international commission, a regime Turkey later replaced on its own terms with the Montreux Convention in 1936.
The most consequential annex was signed separately in January 1923: a convention providing for a compulsory exchange of populations, defined by religion rather than language or self-identification. Roughly 1.2 million Greek Orthodox Christians were moved from Anatolia and eastern Thrace to Greece, and something in the region of 350,000 to 400,000 Muslims moved from Greece to Turkey. Turkish-speaking Orthodox Christians went to Greece; Greek-speaking Muslims went to Turkey. Communities that had lived in place for millennia were uprooted by treaty, and the transfer was largely retroactive, ratifying flight that had already happened in the war.
The two legacies
For Turkey, Lausanne is a founding document and a wound at once. It is celebrated as the moment the republic forced the great powers to accept it as an equal. It is also the object of a persistent nationalist anxiety, the Sevres syndrome, the conviction that outsiders are permanently plotting to partition Turkey and that any concession to minority claims is the first move. Turkish politicians have periodically hinted that Lausanne left Turkey short of territory it should have, particularly in the Aegean and northern Iraq.
For everyone else, its darker inheritance is the population exchange. Lausanne made forced ethnic and religious unmixing a respectable instrument of statecraft, endorsed by the League of Nations and supervised by an international commission. Policymakers cited it approvingly for decades afterward, including in discussions of Palestine in the 1930s, in the transfer of Germans from Eastern Europe in 1945, and in the partition of India in 1947. The idea that peace is easiest when populations match borders, and that the way to get there is to move the people, was normalized in a Swiss lakeside hotel in 1923.
And the Kurds, roughly forty million people today, are the largest ethnic group in the world without a state because a promise made in 1920 was quietly deleted in 1923.