The British still expected the Grand National Assembly to make concessions. From the first speech, the British were startled as Ankara demanded fulfillment of the National Pact. During the conference, the British troops in Constantinople were preparing for a Kemalist attack. There was never any fighting in Thrace, as Greek units withdrew before the Turks crossed the straits from Asia Minor. The only concession that İsmet made to the British was an agreement that his troops would not advance any farther toward the Dardanelles, which gave a safe haven for the British troops as long as the conference continued. The conference dragged on far beyond the original expectations. In the end, it was the British who yielded to Ankara's advances.

The Armistice of Mudanya was signed on 11 October. By its terms, the Greek army would move west of the Maritsa, clearing Eastern Thrace to the Allies. The agreement came into force starting 15 October. Allied forces would stay in Eastern Thrace for a month to assure law and order. In return, Ankara would recognise continued British occupation of Constantinople and the Straits zones until the final treaty was signed.