This campaign battle honour was awarded for the Somme offensive of 1916.  The battle honour covers actions conducted between 1 September and 14 October 1916. During this timeframe the 15th Bn was additionally awarded three other battle honours Pozieres (3 September), Thiepval (26-27 September) and Ancre Heights (5 October).  The campaign battle honour Somme is emblazoned on the Regimental Colour.
This map of the Somme sector from the Regimental history of the 48th Highlanders of Canada  shows locations were the unit was engaged during September and October 1916.
15th Battalion Officers 10 Oct 1916 Somme