# Bizarre pin rule: pinned pieces do not attack

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).

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?
• 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?

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.

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.

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.

• The draw is because after Kf4 White will continue with Bxf3(+), and the bishop will cover the promotion square. Commented Nov 18, 2014 at 12:57
• Google Books has finally made a scan 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 in case the one on Google Books goes down. (Direct link to page 103) Commented Jan 15, 2017 at 16:34

• 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 Daniel'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 Daniel 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.

• 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. Commented Nov 17, 2012 at 20:27
• 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.
– ETD
Commented Nov 18, 2012 at 2:19
• 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? Commented Oct 24, 2013 at 7:26
• 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. Commented Oct 10, 2014 at 20:50
• 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. Commented Oct 10, 2014 at 20:52

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.