During World War II he was a member of the SS, the military branch of the German Nazi Party, with the rank of SS-Hauptscharführer.

Later on Berg came to Kamp Amersfoort concentration camp and became Schutzhaftlagerführer II (second deputy commander) under SS-Obersturmführer Walter Heinrich.

[2] Berg rarely involved himself in atrocities in Kamp Schoorl, but in Amersfoort he frequently mistreated prisoners himself.

Under his leadership, the living conditions of the prisoners were very bad, both due to the abuse and the food rations that were far too small.

His uniform boots as well as the camp commander's original desk are exhibited in the National Monument Kamp Amersfoort since 2018.