[2] Koll then served with his unit on Eastern Front until April 1915, when he was transferred to the staff of 49th Reserve Division as Telephone officer under Generalleutnant Friedrich von Bernhardi.

He assumed command of 70th Radio-Small Battalion in June 1917 and held that assignment for a year, when he was transferred to the staff of 7th Division, operating on the Western Front.

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.

He was assigned to 6th Division in Münster and served as company commander in divisional 6th Motor Transport Battalion until October 1935, when he assumed duty as Adjutant of 2nd Panzer Brigade.

[2] Following the outbreak of World War II, Koll assumed command of 11th Panzer-Regiment assigned to 6th Panzer Division under Generalleutnant Werner Kempf in January 1940 and led his unit during the Battle of France in summer that year.

[2] Koll remained on the Eastern Front until July 1942, participating in the Siege of Leningrad, Battle of Moscow and Rzhev-Vyazma Strategic Offensive Operation and returned to Germany.

He was transferred to the Führerreserve and remained there until September 1942, when he assumed duty as Chief of Motor Vehicle Repair Matters in the Office of Oberkommando des Heeres.

[2] Upon his promotion to Generalmajor on August 6, 1943, Koll became Chief of Repair Matters in the Office of the Oberkommando der Wehrmacht and served in this capacity until November that year, when he was sent to the Infantry School in Döberitz for Division-Leaders course.