Answers.Body: <p>Castling is an incredibly useful in chess: three moves in one. So we don't have to hunt far for reasons why it can be the best move strategically.</p>
  <p>One common comparison is between the castling and the rook move to the d file or f file. Basically the king may need to move offensively, or defensively:</p>
  <ul>
  <li>to cover a flight square for bK,</li>
  <li>to attack a pieces (castling can be double attack),</li>
  <li>to avoid being checked/mated,</li>
  <li>to get out of the way so that the rook delivers check or can move.</li>
  </ul>
  <p>In basic retrograde analysis, castling is used as OP pointed out, to deny the opponent's castling in certain situations.</p>
  <p>In more sophisticated retrograde analysis, under the A Posteriori condition one player captures e.p., which would not normally be allowed, but a later castling &quot;proves&quot; that the e.p. was in fact justified as no other move could have been made.</p>
  <p>In Dead Reckoning, castling may be the only way to keep the game alive, even if the result of the problem is in the end a draw. This also may allow the legality of castling to be deduced through retrograde analysis, without using the conventions. It is not normally possible to reason positively about castling using R.A.</p>
  <p>In an antique version of the conventions, it was thought that castling would reset the counter for draw by 50 moves. So a few problems by Plaksin exploit this trick. This is still a matter of controversy even today.</p>
  <p>There are also joke problems involving &quot;playing at odds&quot; so one player is missing a rook, but is still allowed to castle with the king moving twice, even though no rook actually moves. I don't know whether occupation of the vacant corner square would be enough to demolish the castling right, generally not, as some of these problems have a rook on the haunted corner square which did not originate there, either coming from the other side or promoting.</p>
  <p>I'm aware this is a all bit dry so far, but we could find examples of all of these ideas if folk are interested.</p>
  
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-04-08T10:48:15.907Z
Answers.Text: My idea was SCHWALBE 4/2021, #18518. (PM@MPF for the position)
Answers.UserDisplayName: Hauke Reddmann
Answers.ContentLicense: CC BY-SA 4.0
Answers.CreationDate: 2021-02-16T11:47:57.690Z
Answers.LastActivityDate: 2021-02-16T11:47:57.690Z
Answers.UserDisplayName: Laska
Body: <p>I recall at least one game of mine where my last move was castling (around move 20 or so :-), it saved my ugly posterior, it was the only move and we immediately agreed on a draw after that. (Do not try this at home, kids.)</p>
  <p>I see the following ways of castling being the only winning move.</p>
  <ul>
  <li>Retro: Under some convention, one side castles to prove the other can't.</li>
  <li>Tactical 1: Again, the king's posterior is on fire, and after that is solved, material wins. (Happened.)</li>
  <li>Tactical 2: Double attack on a stupid incoming Rb2 and Kd8 - yes, that happened more than once.</li>
  <li>Tactical 3: E.g. after some Nxf2 against the bK, with great shocking value. Ditto. So lets file everything else in this spirit under &quot;Various Tactical&quot;.</li>
  <li>Positional: This is the only way to get the rook past the king and out of the pawn forest. (Very study-like. Probably never happens in a game.)</li>
  </ul>
  <p>What are other ways in which castling may the only winning move in any given position?</p>
  
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-14T16:41:00.227Z
Comments.Text: The difficulty is that the question by this distinguished, witty and imaginative composer is open-ended - the kind that might easily find a place in Worldbuilding or Writing SEs. It is quite detailed enough to give an idea what it’s asking for. Unfortunately, here in Chess SE, we seem stuck with a fallacious expectation that questions must be factual and wooden. Of course the question should be re-opened immediately, and I have voted that way. Please vote to re-open
Comments.UserDisplayName: Laska
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-14T19:10:50.050Z
Comments.Text: Thanks for the flowers, but I never argue with the mods. Even if I'm in the right, i.e. always :-) (I sent my idea to the SCHWALBE instead. If they find it too small, it goes to MatPlusForum. Also, it actually was a spawnoff of another question I maybe ask later.)
Comments.UserDisplayName: Hauke Reddmann
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-15T10:57:20.937Z
Comments.Text: I remember seing a beautiful study or problem were 1.0-0 ! was the key just because White needed to have both e1 and h1 available for other pieces. I don't know how to look for it however.
Comments.UserDisplayName: Evargalo
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-15T12:16:02.817Z
Comments.Text: Don't worry, I'm a problem composer, I know which one you mean :-) (Since it was no study, it doesn't fit in here. BTW, once did the same with 1.O-O-O.)
Comments.UserDisplayName: Hauke Reddmann
Comments.ContentLicense: CC BY-SA 4.0
Comments.CreationDate: 2021-02-15T16:29:58.147Z
Comments.Text: In a more direct sense: As a general rule, if you can think of something silly Eric Rosen has probably [done it](https://www.youtube.com/watch?v=UxZc7ZF2uOY) against his subscribers at least [twice](https://www.youtube.com/watch?v=uC_RqsMGDVE).
Comments.UserDisplayName: user3482749
Tags: <problems><puzzles><castling><a-posteriori>
Title: Reasons why castling may be the only winning move
ThreadText: # Reasons why castling may be the only winning move
  
  (Asked by: username_0 on 2021-02-13)
  
  I recall at least one game of mine where my last move was castling (around move 20 or so :-), it saved my ugly posterior, it was the only move and we immediately agreed on a draw after that. (Do not try this at home, kids.)
  
  I see the following ways of castling being the only winning move.
  
  * Retro: Under some convention, one side castles to prove the other can't.
  * Tactical 1: Again, the king's posterior is on fire, and after that is solved, material wins. (Happened.)
  * Tactical 2: Double attack on a stupid incoming Rb2 and Kd8 - yes, that happened more than once.
  * Tactical 3: E.g. after some Nxf2 against the bK, with great shocking value. Ditto. So lets file everything else in this spirit under "Various Tactical".
  * Positional: This is the only way to get the rook past the king and out of the pawn forest. (Very study-like. Probably never happens in a game.)
  
  What are other ways in which castling may the only winning move in any given position?
  
  **Tags:** problems, puzzles, castling, a-posteriori
  
  > **Comments:**
  > **username_1**: The difficulty is that the question by this distinguished, witty and imaginative composer is open-ended - the kind that might easily find a place in Worldbuilding or Writing SEs. It is quite detailed enough to give an idea what it’s asking for. Unfortunately, here in Chess SE, we seem stuck with a fallacious expectation that questions must be factual and wooden. Of course the question should be re-opened immediately, and I have voted that way. Please vote to re-open  
  > **username_0**: Thanks for the flowers, but I never argue with the mods. Even if I'm in the right, i.e. always :-) (I sent my idea to the SCHWALBE instead. If they find it too small, it goes to MatPlusForum. Also, it actually was a spawnoff of another question I maybe ask later.)  
  > **username_2**: I remember seing a beautiful study or problem were 1.0-0 ! was the key just because White needed to have both e1 and h1 available for other pieces. I don't know how to look for it however.  
  > **username_0**: Don't worry, I'm a problem composer, I know which one you mean :-) (Since it was no study, it doesn't fit in here. BTW, once did the same with 1.O-O-O.)  
  > **username_3**: In a more direct sense: As a general rule, if you can think of something silly Eric Rosen has probably [done it](https://www.youtube.com/watch?v=UxZc7ZF2uOY) against his subscribers at least [twice](https://www.youtube.com/watch?v=uC_RqsMGDVE).  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2021-02-16. Score: 2 | Accepted answer
  
  Castling is an incredibly useful in chess: three moves in one. So we don't have to hunt far for reasons why it can be the best move strategically.
  
  One common comparison is between the castling and the rook move to the d file or f file. Basically the king may need to move offensively, or defensively:
  
  * to cover a flight square for bK,
  * to attack a pieces (castling can be double attack),
  * to avoid being checked/mated,
  * to get out of the way so that the rook delivers check or can move.
  
  In basic retrograde analysis, castling is used as OP pointed out, to deny the opponent's castling in certain situations.
  
  In more sophisticated retrograde analysis, under the A Posteriori condition one player captures e.p., which would not normally be allowed, but a later castling "proves" that the e.p. was in fact justified as no other move could have been made.
  
  In Dead Reckoning, castling may be the only way to keep the game alive, even if the result of the problem is in the end a draw. This also may allow the legality of castling to be deduced through retrograde analysis, without using the conventions. It is not normally possible to reason positively about castling using R.A.
  
  In an antique version of the conventions, it was thought that castling would reset the counter for draw by 50 moves. So a few problems by Plaksin exploit this trick. This is still a matter of controversy even today.
  
  There are also joke problems involving "playing at odds" so one player is missing a rook, but is still allowed to castle with the king moving twice, even though no rook actually moves. I don't know whether occupation of the vacant corner square would be enough to demolish the castling right, generally not, as some of these problems have a rook on the haunted corner square which did not originate there, either coming from the other side or promoting.
  
  I'm aware this is a all bit dry so far, but we could find examples of all of these ideas if folk are interested.
  
  > **Comments:**
  > **username_0**: My idea was SCHWALBE 4/2021, #18518. (PM@MPF for the position)  
  
  ---
  
  