en passant

This article uses algebraic notation to describe chess moves.

En passant (from French: in passing) is a move in the board game of chess. En passant is a special capture made immediately after a player moves a pawn two squares forward from its starting position, and an opposing pawn could have captured it if it had moved only one square forward. In this situation, the opposing pawn may capture the pawn as if taking it "as it passes" through the first square. The resulting position is the same as if the pawn had only moved one square forward and the opposing pawn had captured normally. The en passant capture must be done on the very next turn, or the right to do so is lost.^[1] Such a move is the only occasion in chess in which a piece captures but does not move to the square of the captured piece. If an en passant capture is the only legal move available, it must be made.

This rule was added in the 14th or 15th century when the rule about pawns having the option of initially moving two squares was added. The rationale is so that a pawn cannot pass by another pawn using the two-square move without the risk of it being captured.

In either algebraic or descriptive chess notation, en passant captures are sometimes denoted by "e.p." or similar, but such notation is not required. In algebraic notation, the move is written as if the captured pawn just advanced only one square, e.g, exf6 (or exf6 e.p.) in the illustration below.

Illustration

Example of en passant

Black to move The black pawn is in its initial location. If it moves to f6 (×), the white pawn could capture it.

White to move Black moved his pawn forward two squares from f7 to f5, "passing" f6.

Black to move On the next move, White captures en passant, capturing the pawn as if it had moved to f6.

Threefold repetition and stalemate

When claiming a draw by threefold repetition, two positions whose pieces are all on the same squares, with the same player to move, are considered different if there was an opportunity to make an en passant capture in the first position, because that opportunity by definition no longer exists the second time the same configuration of pieces occurs.

Kenneth Harkness wrote that it is frequently asked if an en passant capture must be made if it is the only move to get out of stalemate (Harkness 1967:49). This point was debated in the 19th century, with some arguing that the right to make an en passant capture is a "privilege" that one cannot be compelled to exercise. The rules of chess were amended to make clear that the capture was mandatory in that instance (Winter 1999). Today, it is settled that the player must make that move (or resign). The same is true if an en passant capture is the only move to get out of check (Harkness 1967:49).

Examples in the opening

Petrov defense line, after 5... d7-d5, the white pawn on e5 may capture en passant.

In this line from the Petrov Defence, White can capture the pawn on d5 en passant on his sixth move.

• 1. e4 e5
• 2. Nf3 Nf6
• 3. d4 exd4
• 4. e5 Ne4
• 5. Qxd4 d5 (diagram)
• 6. exd6 (Hooper & Whyld 1992:124-25).

Another example occurs in the French Defense after 1.e4 e6 2.e5, a move once advocated by Wilhelm Steinitz. If Black responds with 2...d5, White can capture the pawn en passant with 3.exd6. Likewise, White can answer 2...f5 with 3.exf6.

Example from game

Gundersen-Faul, 1928

Position after 12... f7-f5.

Gundersen-Faul

After 14... g7-g5. White wins by taking the pawn en passant, which results in checkmate.

Black has just moved his pawn from f7 to f5 in this game between Gunnar Gundersen and A. H. Faul.^[2] White could capture the f-pawn en passant with his e-pawn, but had a different idea:

• 13. h5+ Kh6
• 14. Nxe6+ g5
• 15. hxg6 e.p. #

The en passant capture places Black in double check from White's rook on h1 and bishop on c1. Since Black cannot parry both checks at once, and his last route of escape, moving to g7, is blocked by White's knight at e6, he is checkmated.

Historical context

Historically, allowing the en passant capture is one of the last major rule changes in European chess that occurred in the 14th to 15th century, together with the introduction of the two-square first move for pawns, castling, and the unlimited range for queens and bishops. Asian chess variants, because of their separation from European chess prior to that period, do not feature any of these moves (Davidson 1949:14,16,57).

The motivation for en passant was to prevent the newly-added two-square first move for pawns from allowing a pawn to evade capture by an enemy pawn. Specifically, the rule allows a pawn on a player's fifth rank the opportunity to capture the opponent's pawn on an adjacent file that advances two squares from its starting square as though it had only moved one square.

Notes

References

• Davidson, Henry (1949), A Short History of Chess, McKay, ISBN 0-679-14550-8 (1981 paperback) 
• Golombek, Harry (1977), Golombek's Encyclopedia of Chess, Crown Publishing, p. 216, ISBN 0-517-53146-1 
• Harkness, Kenneth (1967), Official Chess Handbook, McKay 
• Hooper, David; Whyld, Kenneth (1992), The Oxford Companion to Chess (second ed.), Oxford University Press, ISBN 0-19-866164-9 
• Just, Tim; Burg, Daniel B. (2003), U.S. Chess Federation's Official Rules of Chess (fifth ed.), McKay, ISBN 0-8129-3559-4 
• Schiller, Eric (2003), Official Rules of Chess (second ed.), Cardoza, ISBN 978-1-58042-092-1 
• Sunnucks, Anne (1970), The Encyclopaedia of Chess, St. Martin's Press, ISBN 978-0709146971 
• Winter, Edward (1999). "Stalemate". Chesshistory.com. http://www.chesshistory.com/winter/extra/stalemate.html. Retrieved on 2009-06-12.