Feldartillerie-Regiment of the Royal Bavarian Army in Erlangen as a Fähnrich (officer candidate) on 6 July 1903.

[1] Hartmann's course of instruction was interrupted by the outbreak of World War I and he returned to his regiment in the field on 8 August 1914.

On 4 June 1918, Hartmann was assigned to the general staff of the Ottoman Eastern Army Group as Oberquartiermeister.

[1] After the end of World War I, Hartmann remained in service in the Reichswehr, serving primarily as a staff officer.

On 1 February 1926, he was promoted to Major, and on 1 October 1926, he was transferred to the Ministry of the Reichswehr, where he served as an intelligence and counterintelligence officer.

(Bayerisches) Artillerie-Regiment on 1 October 1931 but one year later returned to the intelligence section of the Ministry of the Reichswehr.

On 30 September 1935, Hartmann's activity in Moscow came to an end and he passed on his responsibilities to his successor Ernst-August Köstring, who took over the position on 1 October.

[1] With the 26 August 1939 mobilization of the Wehrmacht for World War II, Hartmann was given command of the newly-formed XXX.

[3] At the start of the Battle of France, the corps initially remained on the defensive, with the goal of tying down French forces, and then from 12 June 1940 commenced offensive operations against the Maginot Line, fighting in France until the Armistice of 22 June 1940.

Due to serious illness after a reaction to a typhus immunization, Hartmann was hospitalized in early 1941 and thus left the corps before the start of the campaign against Greece.