Not as out of character as you may think given MG's fascination with mediaeval warfare, Grunts! was inspired by a late-night drinking session with Neil Gaiman, er, the pleasant concept of a crossover between Tolkien's orcs and the Vietnam War, at least as depicted in popular film.
Basically, a dragon capable of transdimensional hoard-accumulation has accumulated a stash of US Marines materiel and guarded its hoard with the curse 'You are what you wear.' Cue a troop of Orcs led by the fearsome Ashnak who come and raid the place. Cue some very amusing hi-jinks which unfortunately (markdown for this possibly) do not really get jolted out of the joky style even (for example) when our anti-heroes attack a provisions train and if there was a Geneva Convention, well, they'd break it so bad it might as well never have existed. That might put people off, at least nowadays.