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Is there a forced win for White or Black in the chess variant CastleChess? The rules are explained in this post on an obscure blog named “Cinquante signes”, although it is originally from chessvariants.com.

The rules are the same as the orthodox ones, but with two big differences.

White wins via checkmate or if Black can no longer castle queenside. If either the Black king or queenside rook move, of if the rook is captured, Black can no longer preform queenside castling, and thus they lose.

Black can win by giving mate or castling queenside.

The devil is in the details, and there are some questions on the blog that help give insight into whether or not it can be solved.

Q.(b): Is it easy for Black to castle long (and immediately win the game)?

Well, if White is not prudent, yes -in theory, 5 moves are enough for Black to win.

Q. (c): Are draws still possible?

Oh yes, if it's White turn to play for instance, and White is (a) not in Check (b) in check if it moves, the game is a draw (as in orthodox chess).

Q. (e): Do you have any strategic advice?

Yes-there are weaknesses in Black's position. White could focus on: the pawns a7, b7 and f7 for instance.

Q (f): And what about Black's defense?

This position is solid-and, in a few moves, Black might be able to castle long and win: put all Black pieces on their starting square, except 3 — the e7 pawn is on e6; the b8 Knight is on c6; the f8 Bishop is on b6.

  • Intuition tells me Black should win, but I can provide no proof of that fact – David Sep 9 at 6:19
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    Please mention explicitly that you are linking to your own blog. Otherwise you are abusing SE rules. – Federico Poloni Sep 10 at 8:29
  • Hello Federico, my original post mentioned explicitly that there was a link to my own blog. This mention (and the link) were edited by a certain Rowan Demontay (which I don't know -- neither why he is authorized to edit my posts, well, that's life I guess). BTW, I notice there are a lot (a lot!) of different snipers who like to intervene about the "SE rules" infringed by me. Well, let me breathe and learn how this place functions, no? Have a good day. – Eric ANGELINI Sep 10 at 12:16
  • OK, I should direct this comment to @RowanDemontay then: please do not remove mentions of affiliations posted by someone else. – Federico Poloni Sep 10 at 13:08
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    "neither why he is authorized to edit my posts" Because this is how SE works. Everyone can edit others' posts. (For less experienced users, the edits needs to be approved. Rewan Demontay is not one of the less experienced users.) Similar to Wikipedia and basically Wikipedia except people have credits to their contents. Although edit is supposed to be improving the post and in this case it... not really. – null Sep 12 at 6:10
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A million years ago, a friend showed a very simple variant: One random pawn on each side is marked, and if it's captured (by a move that isn't checkmate), the capturing side loses.

The Danish Gambit was popular that night, but otherwise, people were flinging pawns around, planning to win with the variant rule (I guess you could call it a truly poisoned pawn). I said to my friends that I thought the right strategy was no strategy: Just play chess, and try to win the chess game. You'll lose a few games by chance, but you'll also win a few.

Was I right or wrong, I won't say. Maybe you'll try that variant yourself to test both ways of handling it.

I'm a very big fan of the 3 Check variant (so is Karpov). That game messes with your mind. The nitwits who try to win by delivering a third check run out of sacrificial fuel, while playing normally is dangerous, because the variant rule is often just a matter of tactics (that is, some combination that makes one or two checks while sufficiently exposing the king for more).

I gave this castle chess thing some thought, and I was amused by the different winning conditions. White is likely to go nuts in search of a short combination to prevent castling, while Black (I think) should play normally but with a view toward O-O-O.

Is there a forced win for White? I doubt it, and after that bit of thought, I began to favor Black.

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    That was a typo you couldn't work around? You must really hate the Internet. – friscodelrosario Sep 8 at 23:57
  • Yes friscodelrosario, this is a nice variant (the marked pawn) -- and I've posted myself a similar thingy called "Vowel Pawns" on France Échecs' website and on the Retros mailing list (the marked pawns are the ones on column a and e) asking for a forced win – which was presumably discovered (see more in English here: cinquantesignes.blogspot.com/2020/09/vowel-pawns-vp.html) Best, – Eric ANGELINI Sep 9 at 19:15

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