The Treaty of Lausanne, signed in Switzerland in July 1923, officially settled the conflict between the Ottoman Empire and the Allied forces. Not only did the Treaty establish the borders of the modern Turkish republic, but it also defined boundaries, political systems, and understandings of citizenship in the newly formed post-Ottoman nation-states. Here, Hans-Lukas Kieser recounts how the eight dramatic months of the Lausanne Conference concluded more than ten years of war and genocide in the late Ottoman Empire. Crucially, the Treaty was in favour of a homogeneous Turkish state in Asia Minor and became the basis for the compulsory 'unmixing of people' that facilitated the persecution of minority groups, including Armenians, Kurds, and Arabs. Not only did this significant yet oft-overlooked treaty mark the end of the League of Nations' project of self-determination and security for small peoples, but it was crucial in shaping the modern Middle East, and dictatorships in Turkey and Europe.