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Triangle Mate

Triangle mate is a queen mate where the queen, the king, and the escape squares form a triangle shape around the corner. The queen steps to the edge square, and the white king protects it, so the king cannot take it.

The finished shape

This is the finished shape. Triangle mate is a queen mate where the queen, the king, and the escape squares form a triangle shape around the corner.

FEN: k7/1Q5p/1K6/8/8/8/8/8 b - - 1 1

a b c d e f g h
8 k . . . . . . . 8
7 . Q . . . . . p 7
6 . K . . . . . . 6
5 . . . . . . . . 5
4 . . . . . . . . 4
3 . . . . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  a b c d e f g h

The worked example

White plays the mating move here. The queen steps to the edge square, and the white king protects it, so the king cannot take it.

FEN: k7/4Q2p/1K6/8/8/8/8/8 w - - 0 1

a b c d e f g h
8 k . . . . . . . 8
7 . . . . Q . . p 7
6 . K . . . . . . 6
5 . . . . . . . . 5
4 . . . . . . . . 4
3 . . . . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  a b c d e f g h

How to prevent it

Black plays h6 first. The pawn move opens an escape square, so the mate no longer works.

FEN: k7/4Q2p/1K6/8/8/8/8/8 b - - 0 1

a b c d e f g h
8 k . . . . . . . 8
7 . . . . Q . . p 7
6 . K . . . . . . 6
5 . . . . . . . . 5
4 . . . . . . . . 4
3 . . . . . . . . 3
2 . . . . . . . . 2
1 . . . . . . . . 1
  a b c d e f g h

Key points

  • The queen steps to the edge square, and the white king protects it, so the king cannot take it.
  • The worked example ends with Qb7.
  • To prevent it, keep the king off the edge or keep an escape square open.
  • Black plays h6 first. The pawn move opens an escape square, so the mate no longer works.
  • Check every escape square before you play the mating move, because one open square breaks the mate.

Try it Yourself

Edit the code, then press Run.

Running is simulated · Rust Playground

Exercise

Find the checkmate in this position.