Graduating from the War College as a Staff Captain and assigned to the 4th Department of the General Staff, Mustafa Fevzi participated in numerous battles during the prolonged downfall of the Ottoman Empire, such as the First Balkan War and the Battle of Monastir. He was engaged as the Commander of the V Corps throughout the defence of Gallipoli, during which his younger brother was killed in the Battle of Chunuk Bair. He became a Pasha and the Chief of General Staff of the Ottoman Empire after the First World War and was appointed as the commander of the First Army Troops Inspectorate in 1919 by Grand Vizier Ahmet Tevfik Pasha. After briefly serving as War Minister in 1920, Fevzi left to join the dissident Grand National Assembly in Ankara as a Member of Parliament for Kozan.