From the introduction:
Colonel Von Stern (Deceased) is not a happy man. He has to get the Twilight Lord’s third army through the pass before spring. Otherwise the cold weather makes it tricky for the more, awkwardly living, soldiers.
So, what’s left of the 23rd Rifles have been summoned.
Von Stern and his overweight ogre attendant, Hipplewhite usher the group into the command tent and explain the problem: The cannon emplacement in the old dwarf fortress of Nava Rûn. A combined force of the Imperator’s Golden Legion and Dwarf Artisans of the Holy Script.