The Wrong Bishop
A whole extra bishop and pawn, worth exactly half a point
Bishop and pawn versus lone king is trivially winning, with one glorious exception. If the pawn is a rook pawn and the bishop does not control the promotion corner, the defending king just sits in that corner and nothing on earth evicts it. This is the wrong bishop, chess's favorite swindle.
Play this ending (free)Why the fortress holds
In the diagram, White has bishop and pawn more, and the position is a dead draw. The promotion square a8 is a light square; White's bishop lives on dark squares and can never attack a8 or a king standing on it. So Black's king shuffles between a8 and b8, and White's only conceivable progress is to cover b8 with the bishop, but the moment the bishop takes b8 away while the king sits on a8, Black has no legal move and is not in check: stalemate.
That is the whole fortress: every configuration in which White covers all the exits is stalemate, and every configuration that isn't stalemate leaves the king a corner square to shuffle back to. The pawn can never promote; the game can never be won.
The rule and its reach
The test takes one second: rook pawn + bishop of the color opposite to the promotion corner + defending king able to reach that corner = draw. All four conditions matter: a knight pawn wins, the right bishop wins, and if the defending king can't reach the corner in time, the attacker wins the race and the fortress never forms.
The rule radiates through practical play far beyond this exact position. Endgames a piece up get evaluated by it: countless bishop endings reduce to “can I avoid trading down into wrong-bishop + a-pawn?” and countless defenses succeed by forcing exactly that trade. It even shapes middlegame decisions about which rook pawn to grab and which bishop to swap.
Attacking and defending it
Defending a piece down: race to the corner, then do nothing beautifully. Head for the promotion corner the instant the wrong-bishop configuration appears on the horizon; once there, shuffle and let the stalemate geometry protect you. (Play the drill; the fun part is watching every winning try dissolve.)
Attacking with the wrong bishop: your only hope is to keep the defending king out of the corner: cut it off with your king and bishop before it arrives, and win the pawn's race instead. If it slips through, the game is over: no triangulation, no zugzwang, no 50-move patience will ever crack the corner. Save your clock and take the handshake.
Questions
What is the wrong bishop in chess?
A bishop that does not control the promotion square of its own rook pawn (a- or h-pawn). If the defending king reaches that corner, the position is a draw despite the extra bishop and pawn; the king can never be forced out without stalemate.
Why can't the extra bishop and pawn win?
The bishop can never attack the promotion corner square or a king standing on it, and every attempt to cover all the king's corner squares with king, pawn and bishop produces stalemate. The defender just shuffles in the corner forever.
Is the wrong bishop the same as opposite-colored bishops?
No. 'Wrong bishop' means one side's bishop cannot control its own rook pawn's promotion corner. 'Opposite-colored bishops' means each side has one bishop and they travel on different colors: a separate, famously drawish family of endgames.
Does the wrong bishop rule apply to other pawns?
No: only rook pawns. With any other pawn, king and bishop can always evict the defender because the king has squares on both sides of the pawn's path. That is why defenders steer trades toward the a- and h-pawns.
Don't just read it, play it
Every position below is playable right now, free, no signup, against a tablebase-perfect opponent that never gives up and explains every mistake.
The Wrong Bishop
Black to play and draw
The Rook Pawn Corner Fortress
Black to play and draw
The Knight Blockade
Black to play and draw
Follow the full curriculum (free)or sharpen these endings in the Gym