No, this has nothing to do with the Regency era! This is one of a trio of easy line dances I've drawn from The Complete Book on Disco and Ballroom Dancing (1979). It's only sixteen beats long; line dances don't get any easier than that. The name supposedly derives from the floor pattern of the dance:
...first the dancers mobilize, as they move in a line down the side, then they "retreat" backward and perform a "holding" action, before wheeling to the left and "defending" in another direction.
I find it's best not to think too deeply about this. The book states that it's also known as the "Hot Chocolate Line Dance," and it is in fact the same step pattern as the dance "Hot Chocolate" I described in a previous post. (So yes, this is kind of a cheat of a post; the only new material here is the stuff above.)
Bonaparte's Retreat (16 beats)
Grapevine right and point (step side R, cross L front, side R, point L forward)
Grapevine left and point (step side L, cross R front, side L, point R forward)
Back up and point (back R, back L, back R, point L fwd)
Rock and turn (shift weight forward L, back R, forward L; kick R gently forward, and pivot on L foot one quarter counter-clockwise)
Repeat as many times as needed for the music, making a quarter turn at the end of each repetition.