Triangulation in chess: how to lose a move with your king
Learn triangulation: when the key position comes with you to move, walk your king around a triangle and bring the same position back with your opponent to move. Then your king walks in and the pawn breaks through.
The triangle
The key position, but you are to move. Every direct try fails, so hand the move over to Black.
Play Ke5: the first side of the triangle. Ke5 Kc6
1… Kc6 Kc6: the king goes for your c5 pawn.
Play Kd4: your king guards c5 and comes back towards d5. Kd4 Kd7
2… Kd7 Kd7: the king has nothing better.
Play Kd5: the same position as at the start, but now Black is to move. Kd5
Three king moves, Ke5, Kd4 and Kd5, made a triangle and handed the move to Black. Now the black king has to give way.
The king walks in
Black gave way with Kc8. Now your king walks in, along d6, e6 and e7.
Play Kd6: your king takes the square the black king left. Kd6 Kd8
1… Kd8 Kd8: the king blocks your way.
Play Ke6: round the black king. Ke6 Kc8
2… Kc8 Kc8.
Play Ke7: on towards d7. Ke7 Kb8
3… Kb8 Kb8: the king heads for the corner.
Play Kd7: your king is next to c7 and c8. Kd7
Your king got to d7, and the black king is pushed towards the corner.
Lose the move on the way
Your king is far away. Walk it to d5, but time it so that you arrive with Black to move.
Play Kd3: towards the pawns. Kd3 Kc8
1… Kc8 Kc8.
Play Kd4: one step from d5. Kd4 Kd8
2… Kd8 Kd8.
Play Ke5: not d5 yet. This step to the side loses the move you need. Ke5 Kd7
3… Kd7 Kd7.
Play Kd5: the key position, with Black to move. Kd5
The triangle was made on the way: Kd4, Ke5 and Kd5. Now Black is to move in the key position.
The pawn break
The black king is in the corner. Now the pawn break.
Play c6: the pawn offers itself. c6 bxc6
1… bxc6 bxc6: the black pawn takes.
Play Kc7: your king guards b7 and b8. Kc7 c5
2… c5 c5: the black pawn runs, far too late.
Play b7+: one step from queening, with check. b7+ Ka7
3… Ka7 Ka7.
Play b8=Q+: the pawn queens. b8=Q+
The triangle handed the move to Black, the king walked in, and the pawn break did the rest.
Key ideas
- The key position: your king on d5, the black king on d7, your pawns on b6 and c5 against b7. With Black to move, the black king has to give way, and you win.
- With you to move, hand the move over: Ke5, Kd4 and Kd5 make a triangle, and the same position comes back with Black to move.
- The black king can't copy the triangle: c7 and d6 are guarded by your pawns.
- The pawn break c6 comes last, with the black king in the corner: after bxc6 your king steps to c7 and the b-pawn queens.
Common mistakes
- Pushing c6 too early: the black king stays in front of the pawns, and it is a draw.
- Stepping straight back with your king: the black king takes c5.
- Kc7 or Kc8 with the black king on a8: stalemate.