Yes. Besides making sense, it's also explicitly stated in the rules of the game:
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 ...
Can a piece put a king in check even though moving that piece would be an illegal move?
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 ...
Really interesting question. I think the following shows that such a situation is sort of possible, depending on how you define the pin:
[FEN "7k/4p3/8/2KP3r/8/8/8/8 b - - 0 1"]
and 2. dxe6 is illegal.
The check would go from being stopped by both pawns, to being stopped by neither.
No. The touch-move rule can't force you to make an illegal move, and it is not legal to put yourself in check.
Here's what the FIDE laws of chess say:
4.5 If none of the pieces touched in accordance with Article 4.3 or
Article 4.4 can be moved or captured, the player may make any legal
Well, it's a variant (since it's played by your friend and his sister, and probably at least some others), but not a well-known one. I used to think this idea would be only logical until I realized that a King moving into a square attacked by a pinned piece could still be captured by the pinned piece, and even though the opposing King would then be exposed ...
Your description of the computer's suggestions doesn't quite match the position, but if you mean the computer suggests Nxe5, that is correct, as Bxd1 leads to a variation of Legal's Mate.
and white has won a pawn, and has a big lead in development.
This post is in response to RemcoGerlich's request for a source for Annunuki's claim that the rule discussed here is an old rule.
From A History of Chess by H. J. R. Murray, chapter 5, "Chess in the Malay Lands", page 103:
"This leads to a still greater anomaly, a piece which is covering a check is deemed to have no power of giving check to the opposing ...
You're referring to ...Bc8-g4 as a threat. The only threat it makes is ...Bg4xf3, losing time and the bishop pair.
While White has d4 under wraps with a pawn at c3, theere's no ...Nc6-d4 coming to pressure the pinned knight. The f6-knight has to move to a lesser square to prepare ...Qd8-f6, which is nothing because Nb1-d2 is right at hand to prevent a ...
To me one move was clear -
But after 1...cxd5 2.Rc7, although the knight is pinned for a move, Black can easily unpin it by moving the queen to d6, d8, e6, or e8. In fact, the knight is not even fully pinned - Black could move it to c5 and force a queen trade. You've sacrificed the knight for a pawn, and get no lasting pin.
Why 1. ......
To answer the subquestion: "Does anyone know if this is some kind of known chess variant?"
Yes, it is a known chess variant. It goes under several names including PMDNC (Pinned Men Do Not Check), Pin chess, Superpin, or Stevens Principle. Its written history dates back at least to a publication by SJ Stevens in Westminster Papers in 1875.
Part of the problem with Bc5 is that they can respond with Na4, which threatens the bishop and grabs the tempo. Be7 isn't great because its range is inhibited by the knight and it impedes the kingside rook's power on the e file after you castle. Bd6 is nice because it is protected by the pawns, the bishop can be retreated to b8 or c7 while still controlling ...
It sure is a chess variant, and now that you brought it up, it just became of the known kind. I take good note of it, even though I never heard of it before. It does sound illogical, as Daniel's comment highlight, so I don't think regular players would come up with it.
Tell them or not : does it really matter ? Don't be authoritative about the ...
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 ...
I realize that it's hard to give general guidelines here, since every chess position has unique considerations. Still, any rules of thumb would be appreciated. I would rather be right 80% of the time than fly blind and "flip a coin" on these decisions every game.
If he ignores your pin by castling / moving queen / interposing the bishop, you have 2 options :...
Think of it this way:
Check mate is where nothing the opponent can do will save them from having you take their king on the next turn, so even if by putting their king in checkmate, you expose your own king, they can take your king before you can take theirs.
There is NO circumstance in which your actions put your own king into check without an opponent ...
No, that's not a checkmate. The white bishop is currently pinned (in absolute pin because it protects the king from check by Black's rook), so there's no legal move can be made by that bishop.
In short, this situation has no consequences, and you still can touch the king to continue play since touch-move rule doesn't apply for pieces in absolute pin.
Let's stick to one color, white here, and everything we'll say will generally hold true for black as well.
Rule of thumb: On the one hand, you generally don't want to move your king-side pawns (such as h3) when you've castled short, unless you have to, and we will expand on what "have to" entails here. The immediate exception to that is when you decide to ...
One of the key principles of opening play is that control of the center is vitally important. If one of the players has complete control of the center then they can much more easily launch an attack and it is much more difficult for the other player to defend.
A white knight on c3 supports/attacks e4 and d5.
A white knight on f3 supports/attacks e5 and d4. ...
Black cannot exploit the pin with ...Nd4: not at once because the Nc6 itself is pinned, not later because c2-c3 is on your plan anyway. This means that you should not panic and can concentrate on developing before taking measures about the Bg4.
You should not be afraid of a ...Qf6 either. After the later sequence ...Bxf3, Qxf3, Qxf3, gxf3, your king is ...
No, absolutely not. You are putting your king in check first from the Qd5.
If you think about this way: Who could take the other king first since that really is what checkmate is? In this case, Kxg2 Qxg2 captured the white king first, and only after would Bxg8 take the black king...White lost the king first.
Your thought also does not hold up to logic: ...
The rules are clear. A move that puts your king in check is an illegal move (I'll leave it to you to find the reference; you might find the other rules helpful to review once you get there).
You cannot checkmate your opponent's king (or accomplish anything else) with an illegal move. Once you make an illegal move on the board, the following things happen:
A: Let's use bishop for our example. xrayBishopAttacks works if we have the following position:
but it doesn't work if you have this:
The f3 knight is not pinned because there is something else behind it. obstructed takes this into consideration.
B: Once you get the pinned pieces, you can just do XAND to check if the piece you want to move is pinned. If ...
Regarding the question - how to deal with very hard tactics?
I'd suggest moving to an easier tactics book, where everything will be clear for you.
After you will finish that book, move to a more advance book, and you'll find that your tactics abilities are much better.
Below you can find a couple of possible continues after Rxc6 which shows why black ...
This task is nontrivial and cannot be obtained easily or setwise from the available bitboards.
The following solution is an example for how such a task might be done for a generic slider - only obvious substitutions are necessary to convert this code to be usable for bishops, rooks and queens.
First, identify the set of possible pinning pieces by ...
NEVER say never. Rules of thumb are just that. White very commonly plays h3 at an early stage in many variations of the Ruy Lopez, even before Black has committed his K. What often makes this safe is that Black may have already disarranged his own Q-side pawns by ..a6 and ..b5, so he is unlikely to castle over there.
I remember learning this rule of thumb ...
Bd6 is the most active square. No, there's not an immediate threat but it does attack h2 which could turn into something later.
Be7 is too passive. It's not smart to "protect against pins" that haven't even happened yet. There's lots of unpin combinations that actually lead to the pinning side being worse. Also, white can't really capitalize on a ...
Bd6 has two big advantages that haven't been mentioned. The first is that it protects the b8 square for your rook. Your rook naturally belongs on the half-open file, and White really wants to play Bf4 to keep you from doing that. (You can put your bishop on d6 later if that happens, but you've wasted a tempo and exchanging bishops makes it easier for the ...
e7 is a very passive square for the bishop. Since White is expected to castle on the kingside, there is no reason not to prefer ...Bd6 over ...Be7. The pin on the f6 knight is not too much of a problem precisely because a ..Bc7, ..Qd6 continuation is always on the table.
...Bb4 has a similar problem as ...Be7 because after 0-0 the bishop is doing nothing on ...
There are a lot of different defenses to the Queen's Gambit Declined, but in most of them, you do not need to worry too much about white trying to take on c5, and holding it since it is very difficult to keep in most lines.
I am going to post some basic lines that lead to different variations, and some comments about each. This material will give you a very ...
Never do it in front of your castled king (or on the wing where you want to castle), if the opponent hasn't castled yet or castled on the other wing. Doing so weakens your king's fortress and is an open invitation for a storm by the b- or g-pawn.
Generally, in open games (after 1. e4 e5), and especially with Black, the loss of tempo involved in a (preemptive)...