58

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, as would by as using different hands for moving (like promoting a pawn to queen) or moving with a hand and hitting the clock with the other.


51

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 – “I’ll see your $5”… < watches opponent’s face> "… and raise you $20”. By moving the king first, you are making what would otherwise be ...


45

Yes. Besides making sense, it's also explicitly stated in the rules of the game: 3.9 The king is said to be 'in check' if it is attacked by one or more of the opponent's pieces, even if such pieces are constrained from moving to that square because they would then leave or place their own king in check. No piece can be moved that will either expose the king ...


35

Can a piece put a king in check even though moving that piece would be an illegal move? Yes. One way to see why this makes sense is to imagine "checkless chess", a game that is just like chess, but you win by capturing the king, not by delivering checkmate, and no one is forced to move out of check. This game is exactly the same as chess except that it ...


33

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 the reason for the rule saying you can only castle with 1 hand.


30

Yes - the less a position looks like a real chess game, the harder it is to spot if it is illegal or not. Sometimes, retrograde analysis is needed to prove a position can be reached in a legal way. For an example, see the starting position of the Horse Concoction by Harry Goldsteen, which can be proven to be legal. [FEN "8/7P/1P5B/2B1Q1n1/3nn2P/1PRnk1nR/...


27

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 out, the rook move alone could be one or two moves. Maybe, you were just moving your rook, maybe you were castling. The King move, however, does determine ...


22

What rules (if any) cover a situation like this? 3.10.2 of the FIDE Laws of Chess defines when a move is illegal - 3.10.2 A move is illegal when it fails to meet the relevant requirements of Articles 3.1 – 3.9 Articles 3.1 - 3.9 basically describe the moves of the pieces. Inarkiev's move was illegal because it breached 3.9.2 - 3.9.2 No piece can be ...


21

One rationale that I can think of for not allowing the king to move through check parallels that behind the possibility of capturing en passant after a pawn makes a two-square advance. The typical pawn move is just a single square forward, and the possibility of advancing two squares on a pawn's first move was a relatively late addition to the game in ...


20

Here is a well organized list that should validate 99.99%+ of common positions: Board: There are exactly 8 cols The sum of the empty squares and pieces add to 8 for each rank (row) There are no consecutive numbers for empty squares Kings: See if there is exactly one w_king and one b_king Make sure kings are separated 1 square apart Checks: Non-active ...


17

It is basically just a shortcut that cuts the game short by one move once the outcome is obvious. According to Wikipedia, "In early Sanskrit chess (c. 500–700) the king could be captured and this ended the game. The Persians (c. 700–800) introduced the idea of warning that the king was under attack (announcing check in modern terminology). This was done to ...


16

If we define "illegal position" as a position that cannot happen in a game using legal moves, I think that the most difficult to spot would be positions that look normal, but are impossible to achieve. [FEN "2k1rr2/pbpq2b1/1p1p1np1/nB1Pp2p/2P1Pp2/2N2NP1/PPQB1PP1/2KR3R w KQkq - 0 1"] For example this position looks legal, but indeed there is no way how this ...


14

The way I always understood castling is that it allows the player to move his king to safety. But this privilege does not come for free - it comes at the cost of a tempo. If a player was allowed to castle out of check, or over a checked square, then it allows him to postpone this powerful move until the very latest, effectively removing the penalty from the ...


14

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, capturing or promotion) and pressed the clock, it shall be considered and penalized as if an illegal move.


13

In standard play (each player has at least 60 minutes for all the moves) it makes no difference when the illegal moves is spotted the position must be restored to the one before the illegal move even if that was several moves ago. In rapid or blitz Appendix A4 part 2b applies: b. An illegal move is completed once the player has pressed his clock. If ...


12

Hi David and welcome to chess.stackexchange.com. This is a common question. It's illegal to move a king into check, or to leave it in check. This includes moving a king adjacent to the opposing king. If you have no legal moves then the game is over: if your king is in check then you are checkmated and you have lost, otherwise you are stalemated and the ...


12

So if your opponent promotes a pawn to a Queen and accidentally places your Queen on the board instead of his own, can you claim a win because of an illegal move? No, you can't. There is no illegal move until the player either presses the clock or makes another move (after the opponent has moved). Here is what the FIDE Laws of Chess have to say: 3.7....


11

From your description, I'm not sure whether in your childhood games the sort of double move you showed above could only happen at that one point in the game, or could continue to happen. So I don't have much to say, but there is at least an established chess variant (dating back to the early 20th century) in which your indicated sequence of moves could occur ...


11

Castling is the only legal chess move in which two pieces are moved. You can verify this by searching for "FIDE Laws of Chess" and reading "Article 3: The moves of the pieces" (I do not provide the URL here because unfortunately it frequently changes).


11

FIDE Laws of Chess 7.4a If during a game it is found that an illegal move, ..., has been completed, the position immediately before the irregularity shall be reinstated. If the position immediately before the irregularity cannot be determined the game shall continue from the last identifiable position prior to the irregularity. The clocks shall be ...


10

\s*([rnbqkpRNBQKP1-8]+\/){7}([rnbqkpRNBQKP1-8]+)\s[bw-]\s(([a-hkqA-HKQ]{1,4})|(-))\s(([a-h][36])|(-))\s\d+\s\d+\s* Here's a regular expression that I use to ensure that a FEN string is actually valid. It doesn't do any testing for a legal/illegal position, but it's a good starting point.


10

I just posted an answer to this question How did castling originate? and I think it offers a missing part of the answer to this questions as well: What the rationale is, behind not being able to castle out of check. Historically castling was probably two moves (the rook move and the king's leap), that were merged into a double move, because they basically ...


10

Yes, that's legal. For example: [FEN "6k1/6r1/8/8/8/6R1/8/6K1 w - - 0 1"] [SetUp "1"] [CurrentPosition "6k1/6r1/8/8/8/8/6R1/6K1 b - - 1 1"] 1.Rg2 The rook can move along the g-file. This is known as a "partial pin" - the rook is somewhat limited in its movement (and can't go to a3, for example) but it can still move if it still protects the king.


9

Promoting to a piece of the opposite color is an illegal move. Because of the touch move rule, Black must make a different legal move with that pawn, such as promoting to a Black queen. As a penalty for making an illegal move, two minutes are added to White's clock.


9

The FIDE rules say this: 7.5 If during a game it is found that an illegal move has been completed, the position immediately before the irregularity shall be reinstated. If the position immediately before the irregularity cannot be determined, the game shall continue from the last identifiable position prior to the irregularity. Articles 4.3 and ...


9

There is a very important rule for castling with one hand. In the Fide Handbook it is rule 4.1. 4.1 Each move must be made with one hand only. The rule applies for all parts of the move, including capturing, castling and promoting. Now for the reasoning, of why a move needs to be executed with exactly one hand: In case that you are making an invalid ...


9

It was illegal to move the queen here (and any piece in general) if that move put the king in check from another of the opponents pieces. If the player tried to move the queen here they have to put it back and make a legal move. Note that in some nonstandard variation most usually of the blitz speed type the special rules allow you to take the king and ...


8

A piece can give check even when it is pinned. This is the main "exception" to the rule that a pinned piece cannot move. The reason is, your pinned piece giving check "takes" the opposing king first. (In this case, it's your rook at g2 on the g file.) That's BEFORE his bishop would take your king. So by the laws of the game, your friend had to move his ...


7

It is never, ever legal to move into check. Period. No ifs, no buts. No exceptions whatsoever. That's the best way to think about it, since it gives the least scope for confusion. If you want to think of it in terms of capturing the king ending the game, look at it this way: if you move into check, your opponent can capture your king, which immediately ends ...


7

This is an illegal move. Even if the White King is protected, you can never put your King en prise. However, if you were to play such a move and your opponent didn't call it ON THAT MOVE, an interesting scenario arises. Under the FIDE handbook, section 7.5.1, it says that if an illegal move happens during a game, the position before it will be reinstated. ...


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