69 votes
Accepted

Why is it illegal to castle with both hands?

The official procedure to castle is (Schiller 2003:19–20 from Wikipedia): first move the king with one hand and then move the rook with the same hand. By using both hands the player can save time, ...
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  • 806
60 votes

Why is it illegal to castle with both hands?

Disclaimer: this is probably not the answer, but it makes for interesting thinking. This reminds me of a string bet in poker. String bets are illegal, because they can be used to gain information – “...
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51 votes

Was AlphaZero taught castling?

Other answers are right in that AlphaZero was implicitly told that castling is a move that exists, I'll elaborate on how exactly that happens by explaining the inputs and outputs of the neural network....
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50 votes

Was AlphaZero taught castling?

was AlphaZero just given this move It was given this move in the same way that it was given all other moves. It started with complete knowledge of the rules of the game. In machine learning terms, ...
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  • 7,378
42 votes
Accepted

Why can't the king castle in this position?

Executive summary: Black actually can castle, but if he does castle he will lose the knight and the game (due to material loss). Detailed answer: Black and White have equal material. The black ...
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  • 1,010
37 votes
Accepted

Should a chess engine be aware of opposite-side castling?

I'm pretty sure Stockfish doesn't have explicit code that handles opposite-side castling. What it does have is: Some kind of "menace" score for enemy pawns advancing against our king. The ...
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  • 21.1k
34 votes

Why is it illegal to castle with both hands?

I know in general the rules say the hand you move your piece with has to be the one that hits the clock. If you castled with two hands which one would you use to hit the clock? This might be part of ...
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  • 1,142
32 votes
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When is castling needed?

Castling is extremely useful in almost all games. It lets you do two things at once. First, it moves your king from the center to the side of the board, where it is much more difficult to attack for ...
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  • 1,337
31 votes

Why is it illegal to castle with both hands?

Chess rules are all about sequence. If you use two hands, you don't know which happened first. So you always use one hand. First, you make your move, then you hit the clock. As others have pointed ...
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31 votes
Accepted

How often does castling occur in grandmaster games?

If you are prepared to use standard Linux command-line tools like wc and grep then I think my free PGN processor, pgn-extract, will do much of the pre-processing necessary to count games in each ...
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  • 1,541
27 votes

What are pros and cons around banning castling?

It would certainly allow for more attacks due to kings being stuck in the center, but fundamentally changing the game, which in a way dumbs it down, is not good. It would be less complex. I also do ...
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  • 31.9k
22 votes
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Prove that White is not allowed to castle here

This is actually a rather typical retrograde problem, just start with the most basic observations: We see that black is missing both rooks and the f8 bishop. Given black's pawn structure it's easy to ...
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  • 11.8k
22 votes

When is it legal to castle moving the rook first?

Unless this is a trick question, I'd say never: 3.8.2 [] This is a move of the king and either rook of the same colour along the player’s first rank, counting as a single move of the king and ...
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  • 23.8k
21 votes

Is preventing an opponent from castling considered an advantage?

It'll depend on the rest of the position. If it's relatively open, chances are you can keep the opponent's king in the center and launch an attack. This might well be a decisive advantage; preventing ...
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  • 23.8k
20 votes

Can it be proven that 11. 0-0-0+ is legal in this position?

Ok after playing around with a couple of lines, I finally found one line that shows it's still perfectly legal to play long castles for white at move 11, here it is: [Title "possible 11.O-O-O+"] [...
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  • 11.8k
20 votes
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Does a loophole still exist in the defintion of castling?

I suppose what is comes down to is that the way 3.8.2 is written can be argued to have a syntactic ambiguity. 3.8.2 can mean either "This is a move of the king, and either rook of the same colour,...
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19 votes
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How to castle two times in a game

The answer is plain and simple: You cannot castle twice without breaking the rules. The only chance for this thing to happen is that the illegal move (the second castling) stays unnoticed until the ...
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18 votes
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How can you castle legally in Chess960 when the castling rook is on the king's destination square?

The FIDE Laws of Chess actually cover this with a recommendation without mentioning the problem. II.3.2.5.1 When castling on a physical board with a human player, it is recommended that the king ...
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  • 74k
18 votes
Accepted

Can you castle twice in Chess960?

Excellent question. The rules state that this is not possible. Castling can only be done once. This is explicitly mentioned under Guidelines II. Chess960 Rules: II.3.1 Chess960 allows each player to ...
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  • 4,822
16 votes

Does a loophole still exist in the defintion of castling?

Is there any glaring flaw in this rules lawyer case, or is it solid until FIDE fixes it? Yes, there is a glaring flaw in your case. The rook and king have to be on the same rank. This is clear from ...
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  • 74k
16 votes

Should a chess engine be aware of opposite-side castling?

Interesting question. I think it depends on how much bottom-up intelligence the engine has. For example, AlphaZero was given no explicit heuristics, but was able to infer plenty of strategy by playing ...
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15 votes

Can a rook put an opponent's king in check as a result of castling?

Yes, of course he can; you're indeed in check. Imagine if checks didn't exist--then on the next move, if your king hasn't moved, he could just take your king with his rook.
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15 votes

Why is it illegal to castle with both hands?

why is it illegal to castle with both hands? Because the rules say so. From the FIDE Laws of Chess - 7.5.4 If a player uses two hands to make a single move (for example in case of castling, ...
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  • 74k
15 votes

What are pros and cons around banning castling?

I have no real preference either way, but I'll point out that Kramnik based his argument on AlphaZero playing against itself. Because of AlphaZero's style, it might not be the case that these no-...
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  • 21.1k
14 votes
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Did Bobby Fischer castle with a pawn promoted to a rook?

There was a time when the FIDE rules didn't specify that a king and rook need to be on the same rank in order to castle. This meant that, assuming the other requirements for castling were met, it was ...
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  • 1,243
13 votes

Did Bobby Fischer castle with a pawn promoted to a rook?

Not Fischer. But there is the infamous Tim Krabbe vertical castling problem: http://www.futilitycloset.com/2009/12/11/outside-the-box/ Although it appears this was already illegal as of the problem'...
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13 votes
Accepted

Is capturing a piece while castling legal?

No, such a move is illegal, because one requirement of castling is that there be no pieces (of either color) standing between the king and the rook. From the FIDE Rules of Chess, 3.8(b): ...
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  • 23k
13 votes

Why are the symbols 0-0 and 0-0-0 used for castling in algebraic notation?

The castling notation was invented by Johann Allgaier and used for the first time in his 1811 2nd edition of his Neue theoretisch-praktische Anweisung zum Schachspiel. He didn't explain why he came ...
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  • 664
13 votes
Accepted

Is castling possible with a pawn promoted to a rook?

No, according to FIDE's Laws of Chess, castling has to be done along the first rank. §3.8.2: 3.8.2 by ‘castling’. This is a move of the king and either rook of the same colour along the player’s ...
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13 votes

Is castling possible with a pawn promoted to a rook?

This question really needs a diagram with this position: [FEN "8/8/4P3/3p4/2p3p1/1pP1kPPp/1P5P/R3K2R w KQkq - 0 1"] White to mate in 3. Tim Krabbé and Max Pam found the loophole in the rules that ...
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