Some kind of reference to Serbian or Balkan peoples and armies, along with the Koko guy.
They're obviously involved in some kind of conflict with some other force, given how intently their troopers are guarding the entrance to their base.
There's some humorous details on their items, like officer uniforms having knife resistance while the standard uniform does not, almost like it's to stop them from being stabbed in the back, probably a reference to how hated some WW2 officers were and how troops sometimes killed them? Or at least that was a popular myth in some books. It seems the gray army officers are involved in a similar situation/myth.
Tbh, would be interesting if it turned out that they and their base was very close to the surface, or something, as it is they seem to just be stuck in yet another pocket of the massive underground subway and cave system where everything is.