Janet and Mildred were two of the generals. I had figured from about the midpoint of the story (where everybody's gender had been revealed except Maladict's) that Jackrum would also turn out to be a woman, but I was still expecting some kind of supernatural revelation: when it didn't happen, I figured that was just me, because my default for mysteries is myth.

At one point they sang a song with a line like "And the devil will be my sergeant".

I want to see if that song exists or if Terry Pratchett made it up.