Editing Castling (section)

==Castling in chess problems==
Castling features in some [[chess problem]]s. The earliest known study containing castling was published in 1843 by Julius Mendheim.<ref>{{cite web |last1=Hornecker |first1=Siegfried |title=Study of the Month - A short history of endgame study castling I |url=https://en.chessbase.com/post/study-of-the-month-a-short-history-of-endgame-study-castling-i |website=ChessBase |date=30 April 2022 |access-date=1 May 2022}}</ref> 

===Retrograde analysis===
Castling is common in [[retrograde analysis]] problems. By chess problem convention, if a player's king and rook are on their original squares, the player is assumed to have castling rights unless it can be proved otherwise.<ref>{{cite web |title=Codex of Chess Compositions – WFCC, Article 16 |url=https://www.wfcc.ch/1999-2012/codex/#c4 |website=World Federation for Chess Composition |access-date=7 February 2023}}</ref> In some retrograde analysis problems, the solver (who usually plays White) is required to prove that the opponent has previously moved their king or rook and therefore cannot castle. This is sometimes accomplished by castling or by capturing ''[[en passant]]'', thereby disproving other possible game histories.<!--NOTE: The paragraphs above may need to be restructured? Also, please add 1843 study (as in "Study of the Month" citation). Possibly also mention the difference between Partial Retrograde Analysis (must have a solution for all cases) and Retro-Strategy (whichever castling/en-passant is executed first is legal) conventions in retro problems involving mutually-dependent castling/en-passant rights.-->

{{Chess diagram  
| tright
| Armand Lapierre
|  |  |  |  |kd|  |  |rd
|pd|  |pd|  |pd|  |pd|  
|  |pd|  |  |pl|  |  |  
|  |  |  |  |  |  |  |  
|  |  |  |rl|  |  |  |  
|  |  |  |  |  |  |pl|  
|  |  |  |  |  |pl|  |pl
|rl|  |  |  |kl|  |  |
| White to play and mate in two 
}}
The diagram shows a mate in two. 1.Rad1{{chesspunc|?}} 0-0 does not work. The {{chessprobgloss|key}} is 1.0-0-0{{chesspunc|!}} This demonstrates that the white king has not moved yet and that the rook on d4 must therefore be a promoted piece. Therefore, either the black king or black rook has previously moved to let the white rook off the back rank. Therefore Black cannot castle. After any move by Black, 2.Rd8 is mate.<ref>{{cite web |title=Yet another chess problem database |url=https://www.yacpdb.org/#31755 |website=Yet another chess problem database |access-date=28 March 2022}}</ref>
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===Novelty problems===
{{Chess diagram  
| tright
|Siegfried Hornecker
|  |  |  |  |kd|  |  |bd
|  |  |  |  |  |  |  |pl
|  |  |  |  |  |  |  |  
|  |  |  |  |  |kl|  |  
|  |  |  |  |  |  |  |  
|  |  |  |  |  |  |  |  
|  |  |  |  |  |  |  |  
|  |  |  |  |  |  |  |
| Helpmate in three with Koko fairy condition<ref>{{cite magazine |last=Hornecker |first=Siegfried |date=9 October 2011 |title=P1204776 |trans-title= |url=https://pdb.dieschwalbe.de/P1204776 |language=German |magazine=Die Schwalbe |location= |publisher= |access-date=13 July 2022}}</ref> 
}}
Some joke chess problems involve castling with a promoted rook of the opponent's color. In orthodox chess, this would be illegal since the rook would be giving check to the king, but under fairy chess conditions, this might not actually be check.

The diagrammed problem involves castling with an opposing rook under the Koko fairy condition (each piece must end up adjacent to another piece when moving).<ref>{{cite web |title=Chess Problem Fairy Definitions |url=http://www.strategems.net/sections/fairy_defs.html |website=StrateGems – US Chess Problem Magazine |access-date=28 March 2022}}</ref> The solution (Black's move being given first per helpmate convention) is:
:'''1. Bg7 h8=R 2. Bf6 Kg6 3. 0-0 Kh7#'''

where, after 3.0-0, White's rook is not checking the king; a hypothetical capture of the king would result in the rook not being adjacent to any other piece, which is illegal under the Koko condition.

The allowance of castling with a "phantom rook" in handicap games has also been used in joke problems.<ref>{{Cite web |url=https://www.chesshistory.com/winter/extra/castling.html |work=Chess Notes |title=Phantom rook (games played at odds) |last=Winter |first=Edward |author-link=Edward Winter (chess historian)  }}</ref> Many other joke variations on castling are possible.
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====Vertical castling====
{{Chess diagram 
| tright
|C. Staugaard
|  |  |  |  |  |  |bl|  
|  |  |  |  |pl|  |  |  
|  |  |  |  |  |  |  |  
|  |  |  |  |  |  |  |  
|  |  |  |  |  |  |  |  
|  |  |pd|kd|  |  |  |  
|  |  |nl|  |  |  |  |  
|  |  |  |  |kl|  |  |rl
| White to play and mate in two
}}

In 1907, C. Staugaard composed a [[Chess_problem#Types_of_problems|two-mover]] in which White promotes a pawn to a rook and then castles vertically with the newly promoted rook (placing the king on e3 and the rook on e2), since the rook has not moved. In the position on the right, White plays 1.e8=R, and after the forced move 1...Kxc2 castles vertically with the promoted rook, checkmating Black.

Vertical castling, also known as "Staugaard castling" or "Pam–Krabbé castling", has been used in a few [[joke chess problem|novelty chess problems]].<ref>{{cite web| url = https://pdb.dieschwalbe.de/search.jsp?expression=K=%27Staugaard%27| title = Staugaard castling at Die Schwalbe}}</ref><ref>{{cite web| url = https://www.yacpdb.org/#search/Ly8vLy8vLy8vLy9QYW0gS3JhYmJlIGNhc3RsaW5nLCAvLy8xLzEvMS8w/1| title = Pam-Krabbé castling at yacpdb}}</ref>

[[Tim Krabbé]]'s 1985 book ''Chess Curiosities'' includes a problem featuring vertical castling, along with an incorrect claim that the problem's 1973 publication prompted [[FIDE]] to amend the castling laws in 1974 to add the requirement that the king and rook be on the same rank. In reality, the original FIDE Laws from 1930 explicitly stated that castling must be done with a king and a rook on the same rank (''traverse'' in French).<ref>[https://fr.wikisource.org/wiki/R%C3%A8gle_du_Jeu_d%E2%80%99%C3%89checs_de_la_F._I._D._E._(%C3%A9dition_officielle_1930) ''Règle du Jeu d’Échecs de la F. I. D. E. (édition officielle 1930)''], (in French), FIDE, 1930 (via wikisource)</ref> It is unclear whether any historically published sets of rules would technically allow such a move.
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