We already know that an endgame with a pawn and a king against a king is a draw if the pawn is a rook pawn (a-file or h-file) and the defending king occupies one of the key squares. The diagram demonstrates a typical drawn position. No matter which player is to move, the black king cannot be forced out of the corner:
But what if White has another piece to help reach the goal, a bishop?
The bishop’s color (which means, in this context, the color of squares the bishop is confined to) is the crucial element here. The rule is actually very simple:
- If the bishop’s color matches the queening (promotion) square color, the attacking player wins.
- If the colors don’t match, the game is a draw. This is what the wrong rook pawn means.
The position above is the second rule, as the bishop cannot stop the black king from guarding the fortress a8-b8. Even if the bishop blocks the b8 square, the game would end as a draw – stalemate.
But let’s see what happens if we reposition the bishop a bit to fulfil the first rule condition:
White to move: 1. ♗f5 ♚b8 2. a7+ ♚a8 3. ♗e4#
Black to move: 1. … ♚b8 2. ♗f5 ♚a8 3. ♗g4! (tempo) ♚b8 4. a7+ ♚a8 5. ♗f3#
Having a bishop in a chess endgame can create complications when dealing with a rook pawn, as it may be the wrong rook pawn. The bishop’s control over the promotion square of the pawn can determine the outcome of the game. This scenario is referred to as having the wrong-colored bishop, and it can lead to a draw in situations where any other pawn would win. A smart player may use defensive tactics such as sacrificing to reach a drawn endgame.
Let me show you a nice example from a real game. In fact, Black lost the game, but he had an outstanding opportunity to force a draw:
Let’s see the final position (if Black used the correct line) again:
As the pawn is the wrong rook pawn, White doesn’t have a way to stop the black king from following the opposite color path – e7-f8-g7-h8 – to reach the corner, and stay there forever and ever.