Allied troops occupied zones based on the sections of Constantinople (now Istanbul) and set up an Allied military administration early in December 1918. The occupation had two stages: the initial phase in accordance with the Armistice gave way in 1920 to a more formal arrangement under the Treaty of Sèvres. Ultimately, the Treaty of Lausanne, signed on 24 July 1923, led to the end of the occupation. The last troops of the Allies departed from the city on 4 October 1923, and the first troops of the Ankara government, commanded by Şükrü Naili Pasha (3rd Corps), entered the city with a ceremony on 6 October 1923, which has been marked as the "Liberation Day" of Constantinople (Turkish: "İstanbul'un Kurtuluşu") and is commemorated every year on its anniversary.