What is the missing piece (marked
"?") in this configuration of a normal chess game?
BLACK
WHITE
Notice that the Black King is in check by the White Rook.
Here is as far as I have gotten:
(Using algebraic chess notation, where the white King is on h8)
1) The "impossible check" can only happen if a white pawn on c7 captures a black piece on d8.
2) But how did the pawn on c7 arrive there?
a) It must have started the game in column f or g, captured it's way to d6, and then captured it's way to c7.
b) At some point after that, the black pawn moved from d7 to d6.
c) At some point after that, the white rook moved from d8 to d7.
d) At some point after that, a black piece arrived on d8,
in peril of being captured.
3) And what was the black piece that arrived on d8? It could not be a Queen or Rook, because that really would mean that we had an impossible check before the white pawn at c7 captured it. And it cannot be a bishop, because it had no way to arrive if pieces where on c7 and e7. So, it must have been a third knight! Black's 8th pawn at some point queened and turned into a knight.
4) But now I'm stuck.
All I know about the missing piece is that it is not a pawn, and did not result from promotion by a pawn, and it is not giving check to the white king. It could be a white rook, queen, bishop, or knight. It could be a black bishop. Obviously, there is something else in this puzzle that I am not seeing.
I'm stuck (spoiler)
