Castling

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Castling is a composite move of King and Rook at the same time. In standard chess it consists of moving a king two squares towards the rook and executing a jump of a rook over the king.

=Rules= The prequisites for doing it are as follows:
 * the king and the relevant rook must not be moved, considered as castling rights inside a chess position
 * the king must not be in check
 * no square between king's start and final square may be controlled by the enemy

=Irreversibility= While castling is irreversible with respect to the castling rights and resets the position index to determine repetition of positions, castling doesn't reset, but increments the halfmove clock concerning the fifty-move rule.

=Chess960= In Chess960 castling is a move reaching the position just like after standard chess castling, which may be achieved by (a) moving the king to c1 or g1 ant then executing a jump by relevant rook (b) jumping with the rook over a king already placed on c1 or g1 (c) interchanging the positions of king and rook.

=Shogi= A formation achieved after castling is called a castle. This is often contrasted with a castle in the game of Shogi, requiring several moves to complete, but it seems wrong, since chess also has several standard defensive castle formations - like the one after fianchetto of a king's bishop or the one with a knight on g7, often achieved in the Old Benoni. For that reason it might be interesting to use shogi programming concepts of a castle map and an attack map in chess.

=See also=
 * Algebraic Chess Notation - Castling
 * Castling Rights
 * King Safety
 * Novag Micro Chess - Castling bug, CPWTIPC 1981

=Forum Posts=

1982

 * Re: bug in chess program by Bruce C. Wright @ Duke University, net.chess, December 2, 1982
 * Re: Origin of Castling by Bruce C. Wright @ Duke University, net.chess, December 4, 1982

2000 ...

 * Castling legality check by mjlef, Winboard Forum, January 04, 2007
 * Saving castling states and en passant history by Eric Lang, CCC, November 27, 2008 » En passant
 * 0x88 FRC castle questions by Daniel Uranga, Winboard Forum, December 12, 2009 » Chess960

2010 ...

 * Castling legality check by Stef Luijten, CCC, May 03, 2011
 * Castling long by Lyudmil Tsvetkov, CCC, August 05, 2013
 * Castling: A counter-intuitive result by Steven Edwards, CCC, September 03, 2013
 * Abundance of castling vs en passant rights by Kirill Kryukov, CCC, April 14, 2014 » En passant
 * Castling Evaluation by Dennis Sceviour, CCC, August 02, 2016 » King Safety

2020 ...

 * How much is castling worth? by Michael J Sherwin, CCC, August 20, 2022

=External Links=
 * Castling from Wikipedia
 * Artificial castling from Wikipedia


 * Computerschach - Eine Wette, die ich gerne verloren habe by Horst Wandersleben (German) » Fifty-move Rule

=References= Up one Level