How to win with the wrong bishop and a rook's pawn
Learn to win with a bishop and a rook's pawn when the bishop can't cover the promotion square: keep the enemy king out of the corner with the bishop on b8 and your king.
The bishop takes b8
The black king is one step from the corner. Your pawn on a6 already guards b7, and your bishop can take b8 and c7.
Play Be5: the bishop takes b8 and c7. With the pawn guarding b7, the black king is shut out of the corner. Be5 Kd7
1… Kd7 Kd7: the king has to step away.
Play a7: the pawn steps forward, and the bishop still guards b8. a7 Kc6
2… Kc6 Kc6: too late.
Play a8=Q: the pawn queens with check. a8=Q+
The bishop took b8, the pawn took b7, and the king never got to the corner.
Your king takes the corner
The black king wants b7, next to the corner. Your bishop can't take that square, but your king can.
Play Kc8: your king takes b7 and b8 from the black king. Kc8 Kb5
1… Kb5 Kb5: the king goes for the pawn instead.
Play Bc3: the bishop guards the pawn. Bc3 Ka6
2… Ka6 Ka6: the king tries the corner from the other side.
Play Kb8: now your king guards a7 and a8 too. Kb8 Kb5
3… Kb5 Kb5: there is no way in.
Play Kb7: your king guards the pawn's whole road to a8. Kb7
Your king got to the corner first. Now a6, a7 and a8=Q follow, and nothing can stop them.
The bishop on a7
Your king is far away, and the black king is three steps from a8. Every move counts: only one wins each time.
Play Be5: the bishop takes b8 and c7 at once. Be5 Kd7
1… Kd7 Kd7: the king heads for b7 instead.
Play a6: now the pawn guards b7. a6 Kc6
2… Kc6 Kc6: the king heads for b6 and a7.
Play Bd4: the bishop takes b6 and a7. Bd4 Kc7
3… Kc7 Kc7: now it goes for b8.
Play Ba7: from a7 the bishop guards b8 and b6 at once. It blocks its own pawn for a while, but the corner is shut. Ba7
The bishop on a7 holds b8, and the pawn holds b7: the black king can't get to the corner. Now your king walks up.
Bring the king
The corner is shut. Your king walks to b6, then the bishop steps aside and the pawn goes through.
Play Kc4: the king starts walking. Kc4 Kd7
1… Kd7 Kd7.
Play Kb5: on towards b6. Kb5 Kc7
2… Kc7 Kc7: the king guards b6.
Play Ka5: round the black king, towards b6. Black has only king moves, and the king can't stay on c7. Ka5 Kd6
3… Kd6 Kd6.
Play Kb6: your king stands next to the pawn and guards b7 and c7. Kb6 Kd5
4… Kd5 Kd5.
Play Bb8: the bishop steps off a7 to make way for the pawn, and stands on b8 itself. Bb8 Kc4
5… Kc4 Kc4.
Play a7: one step from queening. a7 Kb3
6… Kb3 Kb3.
Play a8=Q: the pawn queens. a8=Q
The bishop shut the corner, the king came up, and the pawn queened. With the wrong bishop, the whole win is keeping the enemy king out of the corner.
Key ideas
- If the enemy king reaches the corner in front of your rook's pawn, it is a draw: your bishop can never cover that square, so nothing drives the king out.
- So the whole win is keeping the king out. Your bishop takes b8, the dark square next to the corner.
- The pawn on a6 guards b7, and your king can take b7 and b8 itself.
- The bishop can even stand on a7, in front of its own pawn: from there it still guards b8 while your king walks up.
Common mistakes
- Pushing the pawn while b8 is open: the king slips into the corner, and it is a draw.
- Walking the king first while the corner is open: the black king gets there first.