You and whose army?
Expression of disbelief in and/or contempt for another's motivational capability. Communicates the attitude that the other person is utterly incapable of forcing anyone to do anything without the assistance of a large, heavily-armed force behind him.
Tough Guy: I already told you. Do it my way!
You: Forget it, pal.
Tough Guy: Okay, I'll MAKE you do it.
You: Yeah? You and whose army?
You: Forget it, pal.
Tough Guy: Okay, I'll MAKE you do it.
You: Yeah? You and whose army?