When the triumvirate fled Istanbul, the army was reduced to a mere 100,000 soldiers (from 800,000), and soon the Aegean Region, the Dardanelles, and Istanbul were occupied. The Treaty of Sèvres, signed in 1920, imposed on what was left of the Ottoman Empire the demilitarization of Istanbul and the creation of an independent Armenia and envisaged the creation of an independent Kurdistan and the assignment of Izmir to temporary Greek administration. The Turkish War of Independence, led by a high ranking officer, Mustafa Kemal (later called Atatürk, which means Father Turk, usually translated as Father of the Turks) – which relied on the remains of the Ottoman army and on private militias before the formation of a new assembly and a new government (1920) and a new army – in the fall of 1922 defeated Greece, which had occupied the Western Anatolia region since 1919.
Having regained sovereignty over Istanbul and the Dardanelles from the occupying allied forces, Mustafa Kemal abolished the Sultanate in 1922 (while maintaining a purely religious caliphate). The Republic was proclaimed in 1923, and the caliphate was abolished in 1924.
A single-party system was established in 1925 – with a short period of multi-party government in 1930 – and ended in 1945. The Kemalist republic was not only ‘laicist’ but also strongly nationalist, as evidenced by its policy towards non-Muslim minorities or Kurds whose revolts were brutally suppressed.