The Evolution of Modern Chess Rules: En Passant

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Former US Chess Federation President John McCrary

The question of whether chess was invented or evolved from earlier games may never be settled. Part of the discussion is semantic, since evolution and invention are two sides of the same coin! Evolution is a series of new inventions that build upon or combine earlier designs. Inventions are steps in evolution.   

Chess rules and customs, even today, are constantly evolving. Through research into old chess literature, I've made some original discoveries regarding how modern rules and customs have evolved to reach their current state. This series will explore some specific rule changes for chess that have evolved over the past few centuries.  

Click below for earlier chapters of John McCrary's Evolution of Modern Chess Rules series:

Part One: Draws

Part Two: White Moves First

Part Three: Castling

Part Four: Pawn Promotion

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EN PASSANT CAPTURES:  

As early as 1200 A.D., pawns have been able to move forward two squares forward on their initial move. The point of contention was if a pawn could use this two-square move to bypass the control of an opposing pawn, and various local rules resulted over the centuries. Some regions simply did not allow the two-square move at all, if it meant passing an opposing pawn; others would not allow the move while defending a check.

In his book The Famous Game of Chesse-Play in 1614, Arthur Saul wrote that a pawn had to have the "leave" of the enemy king to pass, without clarifying what was meant by such "leave.”  

By the early 19th century, two variants existed that either allowed, or disallowed, the en passant capture. The move was present in England and its surrounding regions, while capturing en passant was not allowed in Italy and Germany. The rule difference had its effect on opening theory; for example, in Italy after 1. e4 e6 2. d4 d5 3. e5, Black could play ...f5 without the threat of immediate capture.

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Without the en passant rule in early 19th century Italy, opening theory was much different after 3. ... f5.

Capturing en passant brought with it some unique features. For starters, it's the only way a pawn can attack an opposing pawn, without having a reciprocating attack possible for that opposing pawn. Additionally, it's the only move possible for just one turn, after which it becomes impossible. Thus, some combinations that rely on an "in-between" move may not work when an en passant capture is involved. Lastly, en passant is the only move that can give double-check without the moving piece delivering one of the checks. 

Before the modern rule became universal in the mid-1800s, debates occurred about its proper form in those regions where en passant captures were allowed. Some questioned why it applied only to pawns: After all, pawns pass pieces, and pieces pass each other with impunity -- so why couldn't pawns? Curiously, some printed rules failed to specify that it was limited to the immediate reply, though the idea was expressed clearly by some, showing it was presumably understood. But only in recent decades the rule was clarified to state that, in a triple-occurrence draw claim, a position is not a repetition of an earlier position, if an en passant capture was possible in that first position.

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Black to move .. the knight must deliver check, but the White king is in stalemate .. how to proceed?

There was also much debate regarding whether en passant capture was a "privilege" and thus could be refused, if it was the only legal move to prevent a self-stalemate. That debate would seem to be academic, as such a position would be of rare occurrence, though composed problems and studies presented these issues with more clarity. 

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If en passant was a "privilege," meaning it could be refused as some argued in the 19th century, this game would be drawn by stalemate!

By definition, a composed position has no preceding moves, so having an en passant capture as the first move of a solution became an issue, when it couldn't be known if the preceding move was a double-jump of a pawn. Some problem-composing contests simply prohibited having an en passant as the key move. One composing contest in 1883 allowed an en passant capture as the key move, but only if the position could not have been reached by any hypothetical game in which the capture was illegal. The contest rules stated This device, however, shall under no circumstances enhance the value of a problem.

Today’s modern convention of composed positions, however, does allow an en passant capture as the key move – only if the position could not have been legally reached by a move other than the double-jump that made the en passant legal. If the position could have been reached by another move, the key cannot be an en passant capture.