I played an experimental computer chess game in the 80's where
when a piece was taken it wasn't automatically removed from the
board. Instead the 2 pieces (aggressor & defender) went to a
seperate board and you had a fight controlled by the players. The
more powerful the piece the better it's attack eg. pawns were pretty
defenseless against rooks. The victor of this fight was returned to the
board, but any damage sustained remained so eventually even
pawns could take down more powerfull pieces.
I guess it was an attempt at making chess more like a real battle
(why should the attacking piece always win?), but ended up having
little to do with chess & as far as I know was never commercialised.