Editing Castling (section)

==Rules==

===Description===
During castling, the king is shifted two squares toward a rook of the same color on the same rank, and the rook is transferred to the square crossed by the king. There are two forms of castling:<ref>{{harvcol|Hooper|Whyld|1996|p=71}}</ref>
* Castling {{chessgloss|kingside}} (''short castling'') consists of moving the king to g1 and the rook to f1 for White, or moving the king to g8 and the rook to f8 for Black.
* Castling {{chessgloss|queenside}} (''long castling'') consists of moving the king to c1 and the rook to d1 for White, or moving the king to c8 and the rook to d8 for Black.

===Requirements===
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| White cannot castle queenside because the knight is in the way. White can castle kingside.
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| Black cannot castle on either side because the black king is in check by the white bishop.
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| White cannot castle queenside because Black's queen controls c1. White can castle kingside even though the h1-rook is under attack.
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| Black cannot castle kingside because the white queen attacks f8. Black can castle queenside despite the white queen's attack on b8.
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Castling is permitted provided all of the following conditions are met:{{refn|Article 3.8.2 in FIDE Laws of Chess<ref name="FideLawsOfChess"/>}}
# Neither the king nor the rook has previously moved.
# There are no pieces between the king and the rook.
# The king is not currently in [[check (chess)|check]].
# The king does not pass through or finish on a square that is attacked by an enemy piece.

Conditions 3 and 4 can be summarized by the [[mnemonic]]: {{em|A player may not castle out of, through, or into check.}}

Castling rules often cause confusion, even occasionally among high-level players.<ref>{{cite magazine |title=The Rules of Castling |last1=Korn |first1=Walter |url=http://uscf1-nyc1.aodhosting.com/CL-AND-CR-ALL/CR-ALL/CR1961/CR1961_All.pdf |archive-url=https://web.archive.org/web/20200918234721/http://uscf1-nyc1.aodhosting.com/CL-AND-CR-ALL/CR-ALL/CR1961/CR1961_All.pdf |archive-date=2020-09-18 |url-status=live |magazine=[[Chess Review]] |date=October 1961 |volume=29 |page=298 |access-date=2022-03-03 |quote=on castling, considerable confusion often reigns among beginners }}</ref> [[Alexander Beliavsky]] and [[Viktor Korchnoi]] both had to consult the arbiter during tournaments on whether castling was legal when the rook was on or passed over an attacked square, [[Yuri Averbakh]] once mistakenly thought that Black queenside castling was illegal when b8 was attacked, and [[Nigel Short]] once attempted to castle queenside as Black when d8 was under attack (this was not allowed). Illegal castling has also occasionally occurred in serious games between top players (including [[Gata Kamsky]], Viktor Korchnoi, and [[Richard Réti]]) when they forgot that the king or rook had previously moved and returned to its home square, and has not always been noticed by the opponent. [[Yasser Seirawan]] once accidentally castled queenside as White with his queen's rook on b1 (which was not allowed), and [[Alexander Alekhine]] once "castled his queen" (moving his queen from d1 to b1 and his rook from a1 to c1, which was also not allowed).<ref name=timmer>{{cite book |last=Timmer |first=Robert |author-link= |date=1997 |title=Startling Castling! |url= |location= |publisher=Batsford |pages=41–51, 149 |isbn=0713481374}}</ref> To clarify:
* The rook can be under attack.
* The rook can pass through an attacked square. (White can castle queenside even if Black is attacking b1; Black can castle queenside even if White is attacking b8.)
* The king can have been in check earlier in the game.

===Tournament rules===
{{See also|Rules of chess|Touch-move rule}}

Under FIDE rules and USCF rules, and enforced in most [[chess tournament|tournaments]], castling is considered a king move, so the king must be touched first; if the rook is touched first, a rook move must be played instead. As usual, the player may choose another legal destination square for the king until releasing it. When the two-square king move is completed, however, the player is committed to castling if it is legal, and the rook must be moved accordingly. The entire move must be completed with one hand. A player who attempts to castle illegally must return the king and rook to their original squares and then make a legal king move if possible (which may include castling on the other side). If there is no legal king move, the touch-move rule does not apply to the rook.{{sfn|Just|2019|loc=chapter 1, section 10I}}{{sfn|FIDE|2023|loc=article 4}}

These tournament rules are not commonly enforced in {{chessgloss|friendly game|informal play}} nor commonly known by casual players.<ref>[[William Hartston]] notes in ''Teach Yourself Chess'' that "most chess players refrain from demonstrations of ambidexterity."</ref>

===Castling rights===
An unmoved king has ''castling rights'' with an unmoved rook of the same color on the same rank, even if castling is not legal in that particular position. In the context of [[Threefold repetition|threefold and fivefold repetition]], two otherwise identical positions with different castling rights are considered to be different positions.

{{Chess diagram  
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|Karpov vs. Miles, 1986
|rd|  |  |  |kd|bd|  |rd
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| Position after 22.Nb5
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In a 1986 game between [[Anatoly Karpov]] and [[Tony Miles]],<ref>{{cite web |title=Karpov vs. Miles |year=1986 |website=[[Chessgames.com]] |url=http://www.chessgames.com/perl/chessgame?gid=1068512 |access-date=2022-03-25 |df=dmy-all }}</ref> play continued from the diagrammed position as follows:

: '''22. ... Ra4'''
: '''23. Nc3 Ra8'''
: '''24. Nb5 Ra4'''
: '''25. Nc3 Ra8'''
: '''26. Nb5'''

With his 26th move, Karpov attempted to claim a draw by threefold repetition, thinking that the positions after his 22nd, 24th, and 26th moves were the same. It was pointed out to him, however, that the position after his 22nd move had different castling rights than the positions after his 24th and 26th moves (the rook being unmoved prior to 22. ... Ra4, meaning Black still had castling rights in that position), rendering his claim illegal. As a result, Karpov was penalized five minutes on his clock. After thinking for about ten minutes, Miles decided to [[draw by agreement|agree to a draw]] anyway (even an incorrect claim of threefold repetition is also a draw offer).<ref name=timmer/>
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