Zoë Blade's notebook

En passant

En passant (in passing) is a chess rule.

When a Pawn moves forwards two squares, he can be captured by an opposing Pawn as if he only moved forwards one square. It's as if he had two moves in one, and could have been captured at either point.[1][2][3][4]

This is because, on the scale of the evolution of chess, the Pawn moving two squares at once is a relatively modern change designed to speed up the start of the game. Pawns really did used to take two moves to move forwards those first two squares, and en passant allows you to continue to capture them as if that's still the case. Having said that, I'm unclear why only other Pawns can capture en passant.

It's all too easy to forget this rule, as it so rarely comes into play. This can occasionally have disasterous consequences, such as saving your opponent from what looked like a checkmate.

References

  1. "To take en passant is to capture an adverse Pawn when it advances two steps at the first move. To do this, the taking Pawn must always be at his fifth square. If then an enemy's Pawn on the next file is moved two squares, he can take it off in the same way as if it had been moved only one square. A Pawn can only be taken in passing by a Pawn; never by a Piece." Chess: Theory and Practice Howard Staunton, 1876, p. 57
  2. A Primer of Chess José Capablanca, 1935, pp. 22—24
  3. The Soviet Chess Primer Ilya Maizelis, 2014, ISBN 978-1-907982-99-6, pp. 19—21
  4. "A pawn occupying a square on the same rank as and on an adjacent file to an opponent’s pawn which has just advanced two squares in one move from its original square may capture this opponent’s pawn as though the latter had been moved only one square. This capture is only legal on the move following this advance and is called an en passant capture." "FIDE Laws of Chess taking effect from 1 January 2023" FIDE, FIDE Handbook, Aug 2022

Further reading

Encyclopedias

Chess rules: Check | En passant | Stalemate