Fretter-Pico was born on 6 February 1892 in Karlsruhe, Baden-Württemberg, in the German Empire, joining the Field Artillery Regiment "Grand Duke" (1st Badisches) No.

14) of the Prussian Army in Karlsruhe on 20 September 1910 as an officer candidate, and attended the Military School in Danzig from March to November 1911.

In January and February 1918 he completed general staff training in the high command of the Army Group Duke Albrecht von Württemberg.

In October 1935 he was transferred to the foreign department in the Army High Command and on 1 August 1937 he was promoted to colonel (German: Oberst).

After his return he was appointed Chief of Staff of the General Command of the Saar-Palatinate Border Troops (German: Generalkommandos der Grenztruppen Saarpfalz) in Kaiserslautern.

On 1 March 1941 Maximilian was promoted to major general (German: Generalmajor) and in April of the same year he was briefly transferred to the Führerreserve.

With this unit he fought from the beginning of Operation Barbarossa, the attack on the Soviet Union, in the area of Army Group South.

On 1 November 1941 the division took the city of Artemovsk and, as a measure for the coming winter, expanded it into a supply and refitting center for the 17th Army.

To do this, the division had to bring the city out of range of enemy artillery, which was achieved by further advances to the east and the formation of the Troitskoye-Kalinowo-Kaganowitscha line.

At the beginning of July 1944 he was briefly reassigned to the Führerreserve in order to take over command of the 6th Army in the middle of the month, which was destroyed a little later during the Soviet Jassy-Kishinev operation and then had to be reorganised.