Stumpff joined the army in 1907 and served on the General Staff during World War I. During the Weimar Republic, he served as a staff officer in the Reichswehrministerium. On 1 September 1933, Stumpff, with the rank of lieutenant colonel, became head of personnel in the (illegal) Luftwaffe. After the Luftwaffe became formally legal in Germany because of the Nazis rejection of the terms of the Treaty of Versailles, Stumpff served as its chief of staff from 1 June 1937 until 1 January 1939.