[1] During World War II, he initially served on the Western Front in France as a staff officer of the 12th Army,[1] before being sent in December 1940 to the Balkans.

On 2 March 1941 he arrived in Bucharest, and when the 12th Army participated in the occupation of Greece shortly thereafter he served as a logistics staff officer in Thessaloniki and Athens.

[2] His department of the Gehlen Organization was very helpful to the U.S. intelligence community's efforts to track the movements of Soviet fighter and attack aircraft units.

This ensued when a recruit collapsed from heat exhaustion during a march of the 6/9 Fallschirmjäger Training Company from Nagold on July 25, and died in hospital a week later.

In September 1967, Hepp retired from the Bundeswehr and passed command of II Corps on to Generalleutnant Karl Wilhlem Thilo.