Answers.Body: <p>This post is in response to RemcoGerlich's request for a source for Annunuki's claim that the rule discussed here is an old rule.</p>
  
  <p>From <em>A History of Chess</em> by H. J. R. Murray, chapter 5, "Chess in the Malay Lands", page 103:</p>
  
  <p>"This leads to a still greater anomaly, a piece which is covering a check is deemed to have no power of giving check to the opposing King:  e.g. White, Kg5, Bg4; Black, Ke2, Rf3, Pd3; White can calmly play Kf4 and draw the game."</p>
  
  <p>The surrounding text offers no additional insight.  In the above example, I do not see the draw, but this is part of a section that discusses chess as played by the Bataks, and likely involves other rules that differ from modern chess.  Nonetheless, the reference seems relevant.</p>
  
  <p>Source:  Murray, H. J. R. A History of Chess (Northampton, MA: Benjamin Press, 1985)</p>
  
  <p>As an aside, Murray's 900 page book from 1913, long out of print, was reprinted last year by Skyhorse Publishing for a reasonable price.</p>
  
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Answers.Text: The draw is because after Kf4 White will continue with Bxf3(+), and the bishop will cover the promotion square.
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Answers.Text: Google Books has finally made [a scan](https://books.google.com/books?id=VBYLAAAAIAAJ) of Murray's classic _A History of Chess_ book public-domain (as it should be, for a book published pre-1923); I've [reuploaded it to archive.org here](https://archive.org/details/AHistoryOfChess) in case the one on Google Books goes down. ([Direct link to page 103](https://archive.org/stream/AHistoryOfChess/A_History_of_Chess#page/n115/mode/1up))
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Answers.Body: <h3>Answers</h3>
  
  <ul>
  <li><p>It sure <strong>is a chess variant</strong>, and now that you brought it up, it just became of the <em>known</em> kind. I take good note of it, even though I never heard of it before. It does sound illogical, as Daniel's comment highlight, so I don't think regular players would come up with it.</p></li>
  <li><p>Tell them or not : <em>does it really matter ?</em> Don't be authoritative about the standard ruleset, that would be pointless. If you can see a way to lightly mention the official rules, do it, maybe they care, but if they don't, that's it.</p></li>
  <li><p>These rules are illogical once one understands it's all about capturing the king, as Daniel very well points out. <strong>Yes, they are more complex to understand.</strong></p></li>
  </ul>
  
  <hr>
  
  <h2>Strange things happening</h2>
  
  <p>Here's a position where I think this ruleset allows strange things to happen :</p>
  
  <pre><code>[FEN "8/8/2Rr1k2/4n3/3B4/3K4/8/8 b - - 0 0"]
  
  1... Nxc6 {Is moving an actually pinned piece out of it's pinning direction legal ?}
  </code></pre>
  
  <p>Here, the white rook pins the black one, so the bishop is not pinned, but the knight is. Altogether, white pins black. Black to play, capturing the rook would lead to a legal position, because it indirectly pins the bishop, <em>a posteriori</em> freeing the knight, for there is no check from the just-pinned bishop. I argue this being a legal move is dubious, for the knight <strong>is</strong> pinned, for the time being.</p>
  
  <p>It could be in this ruleset, but I found that to make these rules highly paradoxical. Somehow, you shouldn't be able to get a pinned piece out of its pinning direction — even if later on, it comes back on the board to legitimate it had the right to go away. I feel there's a “meantime” in which the position isn't legal, hence the move shouldn't be.</p>
  
  <p>Let's develop on that “delay” thing :</p>
  
  <pre><code>[FEN "8/3rPK2/2k5/8/8/8/8/8 w - - 0 1"]
  
  1. e8=P {what now ?} (1. e8=B {legal}) (1. e8=R {promoting to a non-bishop-behaving piece is illegal})
  </code></pre>
  
  <p>If the newborn consensus is right — a move ending up with a legal position is legal — then this promotion can only be made to a bishop-behaving piece. Again, I'm not liking the time during which the pawn lets the king vulnerable, but I'm more and more convincing myself that that's just my pinning intuition getting in the way.</p>
  
  <p>
  </p>
  
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Answers.Text: I wonder if it would be workable to say that moving into check was legal, and the opponent could if desired capture the enemy king, but a player whose king was captured would have one last move in which to capture his opponent's king; a situation where both kings were captured would then be a draw.  In such a case, a player who was losing could move into check with impunity if the opponent could not capture him without losing his own king (the player who was losing would welcome the resulting draw), but a player who was winning would seek to avoid letting his opponent secure a draw.
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Answers.Text: Making it legal to move into check would alter the role of stalemates in the endgame; such effect might be minimized if moving into check was only legal in cases where the enemy could not capture the king without subjecting his own king to immediate capture.
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Answers.Text: The rule set still makes sense here.  That capture is a legal move, though the position is quite tricky.  Once the white rook is captured, the black rook is pinning the white bishop, hence black isn't in check.  That "meantime" to which you refer doesn't matter, since White has no power until his turn.
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Answers.Text: Regarding your final paragraph, I side with @Danielδ in that I think the rule still makes perfectly good sense here. I think the paradoxical feeling you have is mostly due to your ingrained sense of what is allowable in terms of standard pins. E.g. you write "the knight **is** pinned after all," but a "pin" in this setting is just a somewhat different beast than in chess proper, and it renders new things (im)possible.
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Answers.Text: Interesting first position! The question is, is white in check? The knight is pinned, but by a piece that is itself pinned. If Nxc6 is legal, then surely the white king is also attacked?
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Answers.Body: <p>To answer the subquestion: "Does anyone know if this is some kind of known chess variant?"</p>
  
  <p>Yes, it is a known chess variant. It goes under several names including PMDNC (Pinned Men Do Not Check), Pin chess, Superpin, or Stevens Principle. Its written history dates back at least to a publication by SJ Stevens in Westminster Papers in 1875.</p>
  
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Answers.Body: <p>Well, it's a variant (since it's played by your friend and his sister, and probably at least some others), but not a well-known one.  I used to think this idea would be only logical until I realized that a King moving into a square attacked by a pinned piece could still be captured by the pinned piece, and even though the opposing King would then be exposed to attack, the first side would already have lost.  Note that though Black leaves himself in check with his move, he still wins because he theoretically captures the King first:</p>
  
  <pre><code>[FEN "8/8/5k2/4r3/8/2B5/8/5K2 w - - 0 1"]
  
  1.Ke1 Rxe1 2.Bxf6
  </code></pre>
  
  <p>Compare with a position in which it's a mate in one for whichever side moves first.  Say White checkmates, then Black has lost <em>even though he can checkmate in one move</em>.  This is due to the same reason that Black won in the previous diagram.  Theoretically, White wins because he can capture the opposing King first:</p>
  
  <pre><code>[FEN "6k1/5ppp/6r1/8/8/1R6/PPP5/1K6 w - - 0 1"]
  
  1.Rb8# Rg1# 2. Rxg8 Rxb1
  </code></pre>
  
  <p>To your second question, I see no reason why you should not let them know the real rules.  You are the best judge of whether he'd be open to learning them.  Don't be overbearing and certainly be willing to play his variant if he obviously doesn't care for the standard rules.  Games are for fun.</p>
  
  <p>And to the extent that it requires consideration of more possibilities, it <em>is</em> more complex tactically.</p>
  
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Body: <p>I found this guy who likes playing chess, but not enough to bother reading the rules; he only plays using a physical board with his sister (she doesn't know the rules either).</p>
  
  <p>The made up rule was this:</p>
  
  <blockquote>
    <p>A pinned piece is <em>not</em> attacking the squares he can't reach the next
    move without exposing the king.</p>
  </blockquote>
  
  <p>Which means, a lot of things can happen:</p>
  
  <ul>
  <li>A king can move to an 'attacked' square if the piece is pinned.</li>
  <li>By removing the pin, the piece now attacks the squares he wasn't (this can result in discovered checks if the king was in one of these squares).</li>
  <li>You can remove a check by pinning the attacking piece.</li>
  </ul>
  
  <p>If you think about it, it requires much more thinking process to play like this. I was at a disadvantage because it is really hard to see these new threats and tactics if you never played like this before.</p>
  
  <p>My questions:</p>
  
  <ul>
  <li>Does anyone know if this is some kind of known <a href="http://en.wikipedia.org/wiki/Chess_variant">chess variant</a>?</li>
  <li>Should I tell them the correct rules even when I know they are not that serious about playing?</li>
  <li>Are these rules more complex to understand than the official pin rules?</li>
  </ul>
  
Tags: <rules><chess-variants><pins>
Title: Bizarre pin rule: pinned pieces do not attack
ThreadText: # Bizarre pin rule: pinned pieces do not attack
  
  (Asked by: username_0 on 2012-11-17)
  
  I found this guy who likes playing chess, but not enough to bother reading the rules; he only plays using a physical board with his sister (she doesn't know the rules either).
  
  The made up rule was this:
  
  > A pinned piece is *not* attacking the squares he can't reach the next
  > move without exposing the king.
  
  Which means, a lot of things can happen:
  
  * A king can move to an 'attacked' square if the piece is pinned.
  * By removing the pin, the piece now attacks the squares he wasn't (this can result in discovered checks if the king was in one of these squares).
  * You can remove a check by pinning the attacking piece.
  
  If you think about it, it requires much more thinking process to play like this. I was at a disadvantage because it is really hard to see these new threats and tactics if you never played like this before.
  
  My questions:
  
  * Does anyone know if this is some kind of known [chess variant](http://en.wikipedia.org/wiki/Chess_variant)?
  * Should I tell them the correct rules even when I know they are not that serious about playing?
  * Are these rules more complex to understand than the official pin rules?
  
  **Tags:** rules, chess-variants, pins
  
  
  ---
  
  ## 4 answers
  
  ### Answer by username_6 on 2012-11-17. Score: 18
  
  Well, it's a variant (since it's played by your friend and his sister, and probably at least some others), but not a well-known one.  I used to think this idea would be only logical until I realized that a King moving into a square attacked by a pinned piece could still be captured by the pinned piece, and even though the opposing King would then be exposed to attack, the first side would already have lost.  Note that though Black leaves himself in check with his move, he still wins because he theoretically captures the King first:
  [FEN "8/8/5k2/4r3/8/2B5/8/5K2 w - - 0 1"]
  
  1.Ke1 Rxe1 2.Bxf6
  
  Compare with a position in which it's a mate in one for whichever side moves first.  Say White checkmates, then Black has lost even though he can checkmate in one move.  This is due to the same reason that Black won in the previous diagram.  Theoretically, White wins because he can capture the opposing King first:
  [FEN "6k1/5ppp/6r1/8/8/1R6/PPP5/1K6 w - - 0 1"]
  
  1.Rb8# Rg1# 2. Rxg8 Rxb1
  
  To your second question, I see no reason why you should not let them know the real rules.  You are the best judge of whether he'd be open to learning them.  Don't be overbearing and certainly be willing to play his variant if he obviously doesn't care for the standard rules.  Games are for fun.
  And to the extent that it requires consideration of more possibilities, it is more complex tactically.
  
  
  ---
  
  ### Answer by username_1 on 2013-11-05. Score: 14
  
  This post is in response to username_8's request for a source for Annunuki's claim that the rule discussed here is an old rule.
  
  From *A History of Chess* by H. J. R. Murray, chapter 5, "Chess in the Malay Lands", page 103:
  
  "This leads to a still greater anomaly, a piece which is covering a check is deemed to have no power of giving check to the opposing King: e.g. White, Kg5, Bg4; Black, Ke2, Rf3, Pd3; White can calmly play Kf4 and draw the game."
  
  The surrounding text offers no additional insight. In the above example, I do not see the draw, but this is part of a section that discusses chess as played by the Bataks, and likely involves other rules that differ from modern chess. Nonetheless, the reference seems relevant.
  
  Source: Murray, H. J. R. A History of Chess (Northampton, MA: Benjamin Press, 1985)
  
  As an aside, Murray's 900 page book from 1913, long out of print, was reprinted last year by Skyhorse Publishing for a reasonable price.
  
  > **Comments:**
  > **username_2**: The draw is because after Kf4 White will continue with Bxf3(+), and the bishop will cover the promotion square.  
  > **username_3**: Google Books has finally made [a scan](https://books.google.com/books?id=VBYLAAAAIAAJ) of Murray's classic _A History of Chess_ book public-domain (as it should be, for a book published pre-1923); I've [reuploaded it to archive.org here](https://archive.org/details/AHistoryOfChess) in case the one on Google Books goes down. ([Direct link to page 103](https://archive.org/stream/AHistoryOfChess/A_History_of_Chess#page/n115/mode/1up))  
  
  ---
  
  ### Answer by username_4 on 2012-11-17. Score: 11
  
  Answers
  
  It sure is a chess variant, and now that you brought it up, it just became of the known kind. I take good note of it, even though I never heard of it before. It does sound illogical, as username_6's comment highlight, so I don't think regular players would come up with it.
  Tell them or not : does it really matter ? Don't be authoritative about the standard ruleset, that would be pointless. If you can see a way to lightly mention the official rules, do it, maybe they care, but if they don't, that's it.
  These rules are illogical once one understands it's all about capturing the king, as username_6 very well points out. Yes, they are more complex to understand.
  
  
  Strange things happening
  Here's a position where I think this ruleset allows strange things to happen :
  [FEN "8/8/2Rr1k2/4n3/3B4/3K4/8/8 b - - 0 0"]
  
  1... Nxc6 {Is moving an actually pinned piece out of it's pinning direction legal ?}
  
  Here, the white rook pins the black one, so the bishop is not pinned, but the knight is. Altogether, white pins black. Black to play, capturing the rook would lead to a legal position, because it indirectly pins the bishop, a posteriori freeing the knight, for there is no check from the just-pinned bishop. I argue this being a legal move is dubious, for the knight is pinned, for the time being.
  It could be in this ruleset, but I found that to make these rules highly paradoxical. Somehow, you shouldn't be able to get a pinned piece out of its pinning direction — even if later on, it comes back on the board to legitimate it had the right to go away. I feel there's a “meantime” in which the position isn't legal, hence the move shouldn't be.
  Let's develop on that “delay” thing :
  [FEN "8/3rPK2/2k5/8/8/8/8/8 w - - 0 1"]
  
  1. e8=P {what now ?} (1. e8=B {legal}) (1. e8=R {promoting to a non-bishop-behaving piece is illegal})
  
  If the newborn consensus is right — a move ending up with a legal position is legal — then this promotion can only be made to a bishop-behaving piece. Again, I'm not liking the time during which the pawn lets the king vulnerable, but I'm more and more convincing myself that that's just my pinning intuition getting in the way.
  
  > **Comments:**
  > **username_6**: The rule set still makes sense here.  That capture is a legal move, though the position is quite tricky.  Once the white rook is captured, the black rook is pinning the white bishop, hence black isn't in check.  That "meantime" to which you refer doesn't matter, since White has no power until his turn.  
  > **username_7**: Regarding your final paragraph, I side with @username_6δ in that I think the rule still makes perfectly good sense here. I think the paradoxical feeling you have is mostly due to your ingrained sense of what is allowable in terms of standard pins. E.g. you write "the knight **is** pinned after all," but a "pin" in this setting is just a somewhat different beast than in chess proper, and it renders new things (im)possible.  
  > **username_8**: Interesting first position! The question is, is white in check? The knight is pinned, but by a piece that is itself pinned. If Nxc6 is legal, then surely the white king is also attacked?  
  > **username_5**: I wonder if it would be workable to say that moving into check was legal, and the opponent could if desired capture the enemy king, but a player whose king was captured would have one last move in which to capture his opponent's king; a situation where both kings were captured would then be a draw.  In such a case, a player who was losing could move into check with impunity if the opponent could not capture him without losing his own king (the player who was losing would welcome the resulting draw), but a player who was winning would seek to avoid letting his opponent secure a draw.  
  > **username_5**: Making it legal to move into check would alter the role of stalemates in the endgame; such effect might be minimized if moving into check was only legal in cases where the enemy could not capture the king without subjecting his own king to immediate capture.  
  
  ---
  
  ### Answer by username_9 on 2015-04-10. Score: 11
  
  To answer the subquestion: "Does anyone know if this is some kind of known chess variant?"
  
  Yes, it is a known chess variant. It goes under several names including PMDNC (Pinned Men Do Not Check), Pin chess, Superpin, or Stevens Principle. Its written history dates back at least to a publication by SJ Stevens in Westminster Papers in 1875.
  
  
  ---
  
  