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You cannot place your King in check, the en passant could be refused and because you are not placing your King in check directly it seems you can move your pawn 2 spaces. However, just like castling, you cannot move your King through check. So, because your King is never threatened in the example position, these moves are legal.

However, should there be rules added, or some deeper look into this scenario? It's not even a well known rule to new players so,

Is it illegal to move your pawn 2 spaces, if doing so would cause the opponent to call en passant and checkmate you?

It's kind of a power move, "no passing, mate"

This should be an illegal move...?

Black wins in this position D4 en passant E3

Black Wins Here

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  • 26
    In general, giving your opponent a mate in one is perfectly legal. Why would we add more rules to cover the situation that you mention? What benefits would that have? Jun 11, 2023 at 3:54
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    Just to point it out, when you force your opponent to checkmate you, that is called a selfmate. There are quite sophisticated selfmate studies out there that go over many moves. I'm sure one can find some that end with en passant.
    – koedem
    Jun 11, 2023 at 8:01
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    A more interesting question would be whether a check can be blocked by a moving a pawn two spaces in circumstances where it could be captured en passant. An en passant capture may be viewed as retroactively causing a pawn that would have moved two spaces to instead only move one (IMHO, the rules of Duck Chess should interpret EP captures in this fashion), and as such one could argue that the pawn which was captured en passant hadn't moved two spaces so as to block the check. On the other hand, the opponent can't prevent the pawn from moving two spaces except by waiving the ability to make
    – supercat
    Jun 11, 2023 at 19:38
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    why do you think this is different from any other situation where you give your opponent mate in 1?
    – njzk2
    Jun 11, 2023 at 21:20
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    Every chess game played to a checkmate conclusion ends with a penultimate move that allows one player to be checkmated, followed by checkmate. This is no different. Jun 12, 2023 at 12:43

4 Answers 4

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Can a pawn move 2 spaces if doing so would cause en passant mate?

Of course! There are no rules which forbid blundering mate in 1, even forced mate in one.

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Yes - Magnus Carlsen did exactly this in a game against Jon Ludwig Hammer. You can see the game: www.chess.com/game/live/66685869281

According to GothamChess' analysis at www.youtube.com/watch?v=TuNtMcx-cNY (13:26), Magnus knew he was in a bad position a few moves earlier, but decided to keep playing for an epic ending. His final move (as black) was pawn to e5. White plays en passant for checkmate.

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    It's delightful that this question has such a concrete answer! Jun 12, 2023 at 8:15
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The only move that are illegal fall into these categories:

  1. Your King ends in check on that move (or checkmate). The King is not in check immediatly following that move. If black has another turn before white got to go, then black could capture whites king (the definition of check).
  2. Your King can not move through check. This really only applies during castling since the King moves 2 squares. If the middle squares are attacked, then one may not castle.
  3. Moving a piece in a way that it can't move. For example moving a bishop like a rook.
  4. Castling when one starts in check. You can't do this. I wont go into why here.

This does none of those things and is, as such, perfectly legal. The black king is not in check (or checkmate) directly at that point. It certainly has not moved through check. And the pawn is permitted to move like that. So, no, its perfectly legal, albeit stupid.

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Take this idea to its logical conclusion.

If a player is never allowed to make a move that puts them in a situation where they will definitively lose; then when the opponent is one move away from a putting the player in checkmate, the player would not be able to perform any move other than a move which prevents said checkmate.

In other words, the opponent isn't actually able to act on the checkmate as the player is forced to resolve it before it happens. So what can the opponent do? Well, he can manufacture a situation where the player cannot avoid the checkmate next turn, a so-called guaranteed-mate-in-one.

Wait... We just said that a player is not allowed to make a move that causes them to 100% lose this game. This guaranteed-mate-in-one is such a scenario. Therefore, the player's previous move would not have been allowed.

In other words, the opponent isn't actually able to act on the guaranteed-mate-in-one, as the player is forced to resolve it before it happens. So what can the opponent do? Well, he can manufacture a situation where the player cannot avoid the guaranteed-mate-in-one next turn, a so-called guaranteed-mate-in-two.

Wait... We just said that a player is not allowed to make a move that causes them to 100% lose this game. This guaranteed-mate-in-two is such a scenario. Therefore, the player's previous move would not have been allowed.

In other words, the opponent isn't actually able to act on the guaranteed-mate-in-two, as the player is forced to resolve it before it happens. So what can the opponent do? Well, he can manufacture a situation where the player cannot avoid the guaranteed-mate-in-two next turn, a so-called guaranteed-mate-in-three.

...

I hope the flaw is apparent here.

The only way to resolve such a game would be through players resigning because they tire of the game, not because they've lost.

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  • @JamesMartin: I regret removing the second section of my answer (due to length) because I specifically addressed that presumed subsequent question :) I think the line is drawn where it is drawn as a reasonable way to force victory to come from a player's tactics and strategy, not an opponent's silly mistake. I'm also wondering if this factors in the fact that one player could distract another player, making it more likely they mistakenly make a move that puts themselves in check. With the role to forbid this, it is the future victor who must make the victorious moves, which is more rewarding.
    – Flater
    Jun 13, 2023 at 23:29

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