As a follow on from the question Is it legal to castle with a "ghost" rook: When is it legal (according to the FIDE Laws of Chess) 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 executed as follows: the king is transferred from its original square two squares towards the rook on its original square, then that rook is transferred to the square the king has just crossed.

The word then implies the king moves first, and the rook second. Also,

4.4 If a player having the move:

4.4.1 touches his king and a rook he must castle on that side if it is legal to do so

4.4.2 deliberately touches a rook and then his king he is not allowed to castle on that side on that move and the situation shall be governed by Article 4.3.1

That would imply that touching both king and rook (but not moving them) commits the player to castling; then, he/she could then move the rook first and only then the king, since that would give the same position on the board as the only legal play at that moment. Still, if I would see that as an arbiter, I'd have a word with the player about this.

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  • I'm perplexed by 4.4.1. How, physically, can a player touch his king and a rook? He has to touch one first (even by a millisecond) and so that becomes the piece he must move. I understood the procedure of castling to be: (1) Touch king (must now move king) (2) Move king two squares and release (normally illegal to move king two squares, unless castling, so this commits to castling. (3) Move rook to other side of king. Touching any piece before the king precludes castling. – Oscar Bravo Sep 4 '19 at 6:04
  • @OscarBravo: With two hands at once? But I thought that was against time control rules... – Kevin Sep 4 '19 at 6:07
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    With big hands, a not too large board and a little practice, it's possible to castle (short) by squeezing the king and rook with your thumb and little finger and twisting your hand to make them change places between f1 and g1. I don't think it has any practical benefit, though. – Glorfindel Sep 4 '19 at 6:14
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    The "and" in "touches his king and a rook" can be read as "and then". Thus, the player touches the king, but does not move it (still possible to play Ke2 etc.), and then touches the rook with the same hand (now Ke2 is out and he has to castle). Just like if I touch an opposing piece that I can capture and then also one of my own pieces that can perform the capture, I have to execute that capture (in this case, the order of touching does not matter). – Annatar Sep 4 '19 at 6:14
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    @OscarBravo The rule doesn't say "simultaneously". But even if it did, you're being overly literal. If a player touches two pieces (with the same hand or not) in such rapid succession that you can't tell which was first, that would be classed as simultaneous. – David Richerby Sep 4 '19 at 9:50

The 2019 Champions Showdown: Chess 9LX (aka Chess 960) currently taking place in St. Louis should have been a clue.

Here is the relevant extract from the FIDE Laws of Chess:

Guidelines II. Chess960 Rules

II.3 Chess960 castling rules

II.3.1 Chess960 allows each player to castle once per game, a move by potentially both the king and rook in a single move. However, a few interpretations of regular chess rules are needed for castling, because the regular rules presume initial locations of the rook and king that are often not applicable in Chess960.

II.3.2 How to castle. In Chess960, depending on the pre-castling position of the castling king and rook, the castling manoeuvre is performed by one of these four methods:

II.3.2.1 double-move castling: by making a move with the king and a move with the rook, or

II.3.2.2 transposition castling: by transposing the position of the king and the rook, or

II.3.2.3 king-move-only castling: by making only a move with the king, or

II.3.2.4 rook-move-only castling: by making only a move with the rook.

Here is one of the starting positions from yesterday's games which gives the possibility of rook-only castling on the queenside:

[fen "nrkrqbbn/pppppppp/8/8/8/8/PPPPPPPP/NRKRQBBN w KQkq - 0 1"]

The kings are already on the queenside castling squares of c1 and c8. All that is required is for the d file rooks to move and castling can be performed by hopping the b rook over the king.

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