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Promotion Traps

A promotion trap punishes a careless promotion. The new queen may be captured, may stalemate, or may allow a counter-promotion.

A promotion answered by a promotion with check

The pawn moves from a7 to a8 and promotes to a queen. The black pawn moves from b2 to b1 and promotes to a queen with check. White must answer the check, so the new queen does not decide the game at once.

FEN: 8/P3k3/8/8/8/8/1p6/7K w - - 0 1

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

A promotion into a capture

The pawn moves from a7 to a8 and promotes to a queen. The rook on b8 captures the queen. The promotion square was defended, so the new queen lasted one move.

FEN: 1r2k3/P7/8/8/8/8/8/6K1 w - - 0 1

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

Key points

  • A promotion square may be defended by the enemy.
  • A queen promotion may stalemate the enemy king and draw the game.
  • A promotion may allow the enemy to promote with check.
  • A promotion race is decided by who promotes with check first.
  • Check the promotion square before you promote.
  • Check the enemy pawn's promotion square too.
  • A trap is avoided by promoting to a different piece or at a different time.

Try it Yourself

Edit the code, then press Run.

Running is simulated · Rust Playground

Exercise

White to move. Which promotion falls into a promotion trap?