Editing Castling (section)

===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>
{{clear}}