From: Entropy13
Subject: Castling Legally
Date: August 19, 2005 12:39:43 PM CDT
To: migmag@pair.com
Hi. I sent this email to ChessCentral.com:
From other sources, I was led to believe that it's illegal to castle if any opponent threatens any square that the king is on, or passes over, or lands on. Another explained that besides these three squares, there could be nothing threatening ANY square along the file on which the King and Rook sit, or between them. Your site gives a third view-that the King and Rook can't be exposed to capture. The other rules are the same-can't be in check, neither has moved, etc. This one thing about the enemy threat is all that puzzles me.
This is a great site with great links and articles. Thanks.
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Then I got this reply:
Hi,
The Rook can be threatened, or exposed to capture, and still castle.
Hope that helps!
Thank you for shopping ChessCentral!
Best,
Janet
Customer Support
www.ChessCentral.com
Home of the Chess Experts
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Now, I know the rules have changed over the centuries, but I just want to know the truth about what is being used now. There seem to be some discrepancies among chess lovers about what is and isn't legal.
Thanks.
Al Strickland
It is true that you can castle when the rook is being threatened.. The reason you can't castle when the blank spaces are being threatened is because the King passes through those spaces, and if something is threatening one of the spaces, that would mean that the king would put itself in check, which is a no no.
Think of it this way. One cannot castle if the King would be in check during any part of the castle, assuming he walks toward and past the Rook instead of simply teleporting to his new position. For example, if White has K on e1 and R on h1, if e1, f1 or g1 are attacked by an enemy piece, castling cannot take place. You can think of it as though the King cannot allow himself to get sniped while performing the castle maneuver.