Following the Armistice, Koll served with Freikorps as a member of the "Guard-Cavalry-Rifle-Division" and took part in the suppressing of Spartacist uprising led by communists. He then served with various Freikorps units until mid-October 1919, when his unit was integrated into newly created Reichswehr. Koll then served as Leader of Signals-Platoon of Reichswehr Group Command 2 under General Roderich von Schoeler in Kassel until January 1921, when he was ordered for instruction to the Pioneer school in Munich.