En passant is a move in chess. It is a special pawn that can only occur immediately after a pawn makes a move of two squares from its starting square, and it could have been captured by an enemy pawn had it advanced only one square. The opponent captures the just-moved pawn "as it passes" through the first square. The result is the same as if the pawn had advanced only one square and the enemy pawn had captured it normally. The en passant capture must be made on the very next turn or the right to do so is lost. En passant capture is a common theme in chess compositions. The en passant capture rule was added in the 15th century when the rule that gave pawns an initial double-step move was introduced. It prevents a pawn from using the two-square advance to pass an adjacent enemy pawn without the risk of being captured.
Conditions
A pawn on its fifth may capture an enemy pawn on an adjacent that has moved two squares in a single move, as if the pawn had moved only one square. The conditions are:
the capturing pawn must be on its fifth rank;
the captured pawn must be on an adjacent file and must have just moved two squares in a single move ;
the capture can only be made on the move immediately after the enemy pawn makes the double-step move; otherwise, the right to capture it en passant is lost.
En passant is a unique privilege of pawns—other pieces cannot capture en passant. It is the only capture in chess in which the capturing piece does not replace the captured piece on its square.
Notation
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 capturing move is written as if the captured pawn advanced only one square; for example,...bxa3 or ...bxa3e.p..
Examples
In the opening
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 Defence 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.exd6e.p. Likewise, White can answer 2...f5 with 3.exf6e.p. An example is from this game by Steinitz and Bernhard Fleissig.
Unusual examples
In the diagram, if Black plays 1...g5+, it seems to checkmate White, but it is in fact a blunder. Black overlooks that White can counter this check with the en passant capture 2. fxg6e.p.#, which cross-checks and checkmates Black. This game is a draw if neither side errs. Another example is this game between Gunnar Gundersen and Albert H. Faul. Black has just moved his pawn from f7 to f5. White could capture the f-pawn en passant with his e-pawn, but instead played: The bishop on c1 effects a discovered check. 14...Kh7 results in 15.Qxg7. The en passant capture and discovered checks place Black in checkmate. An en passant capture is the only way a double check can be delivered without one of the checking pieces moving, as in this case. 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.
In chess compositions
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". In the 1938 composition by Kenneth S. Howard, the move 1. d4 introduces the threat of 2.d5+ cxd5 3.Bxd5#. Black can capture the d4-pawn en passant in either of two ways:
The capture 1... exd3e.p. shifts the e4-pawn from the e- to the d-file, preventing an en passant capture after White plays 2. f4. To stop the threatened mate, Black can advance 2... f5, but this allows White to play 3. exf6e.p. with checkmate due to the decisive opening of the.
If Black plays 1... cxd3e.p., White exploits the newly opened a2–g8 diagonal with 2. Qa2+ d5 3. cxd6e.p.#
An example showing the effect en passant captures have on pins is this 1902 composition by Sommerfeldt:
The move threatens 2.Qf2#. The moves of the black e-pawn are restricted in an unusual manner. The en passant capture 1...exd3e.p.+ is illegal, but is legal. This, however, removes the black king's access to e3, allowing
Historical context
Allowing the en passant capture, together with the introduction of the two-square first move for pawns, was one of the last major rule changes in European chess, and occurred between 1200 and 1600. and a change to the rules on pawn promotion. In most places the en passant rule was adopted at the same time as 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. 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. Asian chess variants, because of their separation from European chess prior to that period, do not feature any of these moves.
The possibility of an en passant capture is relevant to the claim of a draw by threefold repetition. Two positions with the same configuration of pieces, with the same player to move, are for this purpose considered different if there was an opportunity to make an en passant capture in the first position, and that opportunity no longer exists in the second position. In his book on chess organization and rules, International ArbiterKenneth Harkness wrote that it is frequently asked if an en passant capture must be made if it is the only legal move. 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. Today, it is settled that the player must make that move. The same is true if an en passant capture is the only move to get out of check.
