En passant (from French: in passing) is a move in the board game of chess (Brace 1977). It is a special pawn capture which can occur immediately after a player moves a pawn two squares forward from its starting position, and an enemy pawn could have captured it had it moved only one square forward. The opponent captures the just-moved pawn as if taking it "as it passes" through the first square. The resulting position is the same as if the pawn had moved only one square forward and the enemy 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. En passant capture is a common theme in chess compositions.
This rule was added in the 15th century when the rule giving pawns the option of initially moving two squares was introduced. It prevents a pawn from using the two-square advance to pass an adjacent enemy pawn without the risk of being captured.
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A pawn on its fifth rank may capture an enemy pawn on an adjacent file that has moved two squares in a single move, as if the pawn had moved only one square. The conditions are:
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Black to move
The black pawn is on its initial square. If it moves to f6 (marked by ×), the white pawn could capture it.
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White to move
Black moved his pawn forward two squares in a single move from f7 to f5, "passing" f6.
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Black to move
White captures en passant in response, capturing the pawn as if it had moved only one square to f6.
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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 (Burgess 2000:463).
Allowing the en passant capture is one of the last major rule changes in European chess that occurred between 1200 and 1600, together with the introduction of the two-square first move for pawns, castling, and the unlimited range for queens and bishops (Davidson 1949:14,16,57). Spanish master Ruy López de Segura gives the rule in his 1561 book Libro de la invencion liberal y arte del juego del axedrez (Golombek 1977:108). In most places the en passant rule was adopted as soon as the rule allowing the pawn to move two squares on its first move, but it was not universally accepted until the Italian rules were changed in 1880 (Hooper & Whyld 1992:124–25).
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 on its first move as though it had advanced only one square (Davidson 1949:16). Asian chess variants, because of their separation from European chess prior to that period, do not feature any of these moves.
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., bxa3 (or bxa3 e.p.) in this example (Golombek 1977:216).
The possibility of an en passant capture has an effect on 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 (Schiller 2003:27).
In his book about chess organization and rules, International Arbiter 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. In his 1860 book Chess Praxis, Howard Staunton wrote that the en passant capture is mandatory in that instance. The rules of chess were amended to make this clear (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).
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There are some examples of en passant in chess openings. In this line from Petrov's Defence, White can capture the pawn on d5 en passant on his sixth move.
Another example occurs in the French Defense after 1.e4 e6 2.e5, a move once advocated by Wilhelm Steinitz (Minev 1998:2). 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.
Position after 12...f7–f5
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After 14...g7–g5. White wins by taking the pawn en passant, with checkmate.
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Black has just moved his pawn from f7 to f5 in this game between Gunnar Gundersen and Albert H. Faul.[2] White could capture the f-pawn en passant with his e-pawn, but had a different idea:
Note that the bishop on c1 actually effects the check on the king, via a discovered check.
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.
The largest known number of en passant captures in one game is three, shared by three games; in none of them were all three captures by the same player. The earliest known example is a 1980 game between Alexandru Sorin Segal and Karl Heinz Podzielny (Winter 2006:98–99).[3]
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En passant captures have often been used as a theme in chess compositions, as they "produce striking effects in the opening and closing of lines" (Howard 1961:106). In the 1938 composition by Kenneth S. Howard, the key move 1. d4 introduces the threat of 2.d5+ cxd5 3.Bxd5#. Black may capture the d4-pawn en passant in either of two ways:
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