What is Stellengruppe 15

      What is Stellengruppe 15

      I try to find out more about a soldier's life. He was in Staraja-Russa from september - oktober 1942, until he was wounded februari 1943. He belonged to Armégrupp Nord, probably 16 army, 1 Luftwaffe fältdivision. In his soldier book it says he belongs to Stellengruppe 15.

      What I would like to know is: What is Stellengruppe 15.