Gyula Breyer joke composition cooked? I recently bought the delightful book Outrageous Chess Problems by Burt Hochberg, which among other things contains some interesting joke compositions.  I have a question about Problem 102 (diagrammed below; it is also mentioned in another page on this site).

[Title "Gyula Breyer, Magyar Sakkvilag, 1918, White To Play And Win"]
[FEN "1N1bknbr/2p1Pn1p/2K1Rp1p/4pP1B/p3p3/p3P1N1/P6P/8 w - - 0 1"]

The intended solution is exf8=bQ+ (promoting a White pawn to a Black queen; this is the joke).  What I am wondering is whether this intended solution actually wins for White.  My engine, an old version of Rybka, gives the main line as

1...Qe7 2.Nd7 Qxe6+ 3.fxe6 Be7 4.Nf5 Kd8 5.exf7 Bxf7 6.Bxf7 h5 7.Bc4

and so on, with an evaluation of 0.00.  The analysis in Hochberg's book suggests that instead of 4.Nf5, White should
play 4.Kxc7 Bd8+ 5.Kc6 "and wins after 6.Nf5 or 6.Nxe4 with a mating net," but my engine replies to 4.Kxc7 with
4...Bd6+ and thinks that Black is even winning.  Even after 4...Bd8+ 5.Kc6 it doesn't see a win for White.

Is this composition known to be cooked?

Yes, the problem is known to be cooked. The problem is actually a total win for White without a joke promotion.
Therefore, the task of creating a position in which the only way to win is to promote to a Black queen is an open one.
The problem can be found in the Die Schwalbe Chess Problem Database, or Schwalbe PDB for short. The solution engine there actually supports promotion to enemy units. The German notation means this: K=King, D=Queen, T=Rook, L=Bishop, S=Knight, and B=pawn.
The problem is that the normal promotion move 1. exf8=Q+, supposedly refuted by the study, actually wins for White!
[Title "Gyula Breyer, Magyar Sakkvilag, 1918, White To Play And Win"]
[FEN "1N1bknbr/2p1Pn1p/2K1Rp1p/4pP1B/p3p3/p3P1N1/P6P/8 w - - 0 1"]

1. exf8=Q! Kxf8 2. Kd7! {This is the move that Breyer missed!}

The problem is for Breyer’s study is that after 1. exf8=Q+ Kxf8, the move 2. Kd7 more or less leaves Black in a zugwang.
Furthermore, after the joke promotion to a Black queen, the position is indeed a draw as you noted. Stockfish analysis confirms this.
[FEN "1N1bkqbr/2p2n1p/2K1Rp1p/4pP1B/p3p3/p3P1N1/P6P/8 b - - 0 1"]

 1... Qe7 2. Nd7 Qxe6+ 3. fxe6 Be7 4. Nf5 Kd8 5. exf7 Bxf7 6. Bxf7 h5 7. Bc4

The inherent problem with the promotion to a black queen is that Black does not have to play, after  1... Qe7 2. Nd7 Qxe6+ 3. fxe6, 3... Ke7? as Breyer claimed in his analysis. This ends up in a loss for Black in the form of a mate in 5 moves.
(Note that the move 1... Be7? loses to a mate in 5: 1... Be7? 2. Kxc7 Qg7 3. Nxe4 Qg1 4. Nxf6+ Kf8 5. Nbd7+ Kg7 6. Ne8#)
[FEN "3bk1br/2pN1n1p/2K1Pp1p/4p2B/p3p3/p3P1N1/P6P/8 b - - 0 3"]

3... Ke7? {This is an incorrect move, contrary to Breyer’s analysis} 4. Nf5+ Ke8 5. Kb7 Be7 6. Kc8 Bd8 7. e7 Bxe7 8. Ng7# {This is the shortest mate afterward as found by Stockfish}

The correct line for Black to play is 3... Be7! and White has no mating net, thereby drawing the game, as given in your line I showed at the top of this answer.
It is a mystery exactly how the ingenious Breyer missed this possibility in his analysis. The most likely answer, through analysis of Black’s options after 4. Nf5, is that Breyer thought that Black must give up protection of their c7 pawn through a bishop move.
Black has 6 legal moves after 4. Nf5-5 by the bishop and one by the king. The moves Bf8 and Bd8 both lead to a mate in 5: 4... Bf8 Kxc7 Bd6+ 7. Kc8 Bc7 8. Nxf6+ Kf8 9. e7# (among many possible lines) and 4... Bd8 5. h4 Be7 6. Kxc7 Bd6+ 7. Kc8 Bc7 8. Nxf6+ Kf8 9. h4#. Bb4 and Bc5 both lead to shorter mates in 4 with the same basic ideas.
The move 4... Bd6 looks like a tempting refutation but White still wins even after that move. Here is one such winning line for White.
[FEN "4k1br/2pNbn1p/2K1Pp1p/4pN1B/p3p3/p3P3/P6P/8 b - - 0 1"]

4... Bd6 5. h4 Kd8 {Anything else results in a mate in 4} 6. exf7 Bxf7 7. Bxf7 Kc8 8. Nxf6

The end result is a positional win for White, although any normal person would struggle win of course.
The last, only non-bishop move 4... Kd8, therefore, is the ultimate refutation in this study after the joke promotion that Breyer somehow miscalculated.

TL;DR: In conclusion, Gyula Breyer’s joke study is cooked on two faults. A normal promotion actually wins after the line 1. exf8=Q+ Kxf8 2. Kd7!, and Black is in zugzwang
Secondly, in the joke promotion lines after the moves 1. exf8=Black queen Qe7 2. Nd7 Qxe6+ 3. fxe6 Be7 4. Nf5, Black can play the only non-bishop move 4... Kd8! and draw the game.
Overall, the study is refuted by a king move from each side. Therefore, it seems like Gyula Breyer could not, to some degree, properly analyze king moves in the endgame!


Why is g4 the best move in this Queens Gambit accepted line? Doesn't the extra tempo not make up for the lack of king safety?
[FEN "r2q1rk1/1pp1ppbp/p1n2np1/5b2/P1BP4/2N1PN1P/1P3PP1/R1BQ1RK1 w - - 0 1"]

I suppose you have some source that claims 1.g4 is the best move from the diagram position, but which doesn't give any reason for it. I won't try to weigh in on whether it is in fact the best move here, but I will try to articulate a reason or two to play it. First I'll say that I don't think it's the tempo against the bishop that offsets the decreased king safety, but rather other tangible results instead.

To my eye, the primary point in its favor is that White gets one of two potentially desirable outcomes immediately: either (1) Black moves her bishop away from controlling e4, so White gets in the move 2.e4 next, building a nice central pawn duo, or (2) Black responds with 1...Be4, and allows a forcing line that lets White obtain two minor pieces for rook and pawn. (I'll note that my first thought in responding to 1...Be4 was simply to win the bishop pair for White, but that ultimately doesn't look that great, and it was some nudging from Stockfish that revealed this other idea to me.)

The annotations that follow look at these two resulting possibilities in a little bit of detail, offering my scant takes on matters. But I'll note that there are a lot of concrete, tactical ideas in the air here, and the overall situation is more chaotic than I initially thought when first looking at the position.

[Event "?"]
[Site "?"]
[Date "????.??.??"]
[Round "?"]
[White "?"]
[Black "?"]
[Result "*"]
[FEN "r2q1rk1/1pp1ppbp/p1n2np1/5b2/P1BP4/2N1PN1P/1P3PP1/R1BQ1RK1 w - - 0 1"]

1.g4
    {Lessening Black's control of the e4 square by putting the question to
    the bishop.}
1...Bd7
    ( 1...Be4 {Trying to stop White's central expansion, but it allows
    White to force the obtaining of two pieces for a rook and pawn if he
    so chooses.} 2.Nd2 $1 Bd5 {Forced.} 3.g5 $1 Bxc4 {Forced,} 4.gxf6 Bxf1
    {Forced.} 5.fxg7 Kxg7 6.Kxf1 {White's larger piece army offers the
    better prospects, and the airy castle around his king isn't an
    immediate concern, and with proper play shouldn't be an issue.} )
2.e4
    {Establishing an ideal pawn center, though yes at the expense of
    having created a good deal of space around the white king. In fact,
    Black can (and perhaps should) now sacrifice a piece for pawns and
    greater exposure of the white king.}
2...Nxg4
    ( 2...h5 {Another attempt to further expose the white king.} 3.e5 {
    This basically forces Black to go in for the same sort of piece
    sacrifice as in the 2.e4 Nxg4 line given here.}
        ( 3.Nh4 $5 {Another interesting possibility, exploiting the fact
        that the only non-pinned pawn defending g6 has now advanced.} 3...
        hxg4 $2 4.Nxg6 )
    3...hxg4
        ( 3...Nh7 $2 4.gxh5 gxh5 5.Kh2 {Now the white king is no more
        exposed than the black king, and White will be the one with the
        better attack.} )
    4.exf6 Bxf6 5.hxg4 Bxg4 6.Qd3 {Threatening Qxg6. Again I'd wager that
    White's extra piece outweighs the deficit in pawns and the exposed
    king.} )
3.hxg4 Bxg4 4.Be2 Bxf3 5.Bxf3 Nxd4 6.Bg2
    {Black has three pawns for the piece, and has removed much of the
    white king's pawn cover. Nevertheless, Black does not have an
    attacking force at the ready immediately, and I think the long term
    chances should favor White's extra piece.}
*


Why Qxd5 instead of Rxd5? This puzzle on chesstempo caught my eye. We play as Black:
[FEN "1r1r2k/p4pp/2q/2p1p2P/P1P1Pn/B3NP/4Q2P/R6K w - - 0 1"]

1. Nd5

The White queen is under attack, yet one shall not rush and capture it. The White may fork the Black king and queen and then fork two rooks:
[FEN "1r1r2k/p4pp/2q/2p1p2P/P1P1Pn/B3NP/4Q2P/R6K w - - 0 1"]

1. Nd5 Nxe2
2. Ne7+ Kf8
3. Nxc6 Ke8
4. Nxb8 Rxb8

So, we lose a rook here. Therefore, we need to capture the knight. I took the knight with the rook:
[FEN "1r1r2k/p4pp/2q/2p1p2P/P1P1Pn/B3NP/4Q2P/R6K w - - 0 1"]

1. Nd5 Rxd5

Yet, chesstempo wanted me to capture it with the queen:
[FEN "1r1r2k/p4pp/2q/2p1p2P/P1P1Pn/B3NP/4Q2P/R6K w - - 0 1"]

1. Nd5 Qxd5
2. cxd5 Nxe2

So, why do we play Qd5 instead of Rd5? Besides, does it matter for the White whether to play cxd5 or exd5 on the last board as the second move?

After 1...Rxd5 2.cxd5, both queens are attacked. They either both get captured, or (if black moves his to safety) neither is. So black lost the exchange.
After 1...Qxd5 2.cxd5 Nxe2, white has lost a knight.
Cxd5 seems the better capture to me on general grounds (repairs white structure a bit, makes pawn c5 weaker) but that's far less important than the full rook difference between 1...Rxd5 and 1...Qxd5.


Could you show me some very easy mate in 20? I am looking for some puzzles where there is a forced mate in as many moves as possible (ideally 20 or more). Yet the puzzles need to be as easy as possible!

You will probably need to find some puzzles where the defending side has a lot of spite checks to delay the mate.

.

Edit :

I just made a very easy mate in approximately 23. White to move:

It's really really easy since Black can do nothing. But it doesn't totally satisfies me since the position is of course not legal...

There are many:

     [Title "Mate in 20"]
 [FEN "3K1B2/1p6/pp6/rk2N3/b1p5/1pP5/1P2P3/8 w - - 0 1"]

You should search puzzles from the 1900. It was a golden era for chess puzzles. I found a mate in 63 some days ago.

Chessmaster also has a nice collection of interesting(and long) puzzles. There are many sites where you can sort puzzles according to difficulty and turns to mate, but I can't remember any atm.


Which chess GUIs support the chess variants Atomic and King of the Hill? I want to play against Stockfish offline because I'm going on a trip. I downloaded the compiled exe from GitHub since my laptop will have limited Internet connection. After loading it into the Arena GUI I noticed it only supports Chess960. Which GUIs support the chess variants Atomic and King of the Hill?

There are three chess variant GUIs supporting both atomic and king of the hill that I am aware of:

PyChess
WinBoard/XBoard
Cutechess

The latter is well suited for automated engine matches and human vs. engine games, but less for game analysis. All three should work fine with the multi-variant Stockfish you downloaded.


Eye strain from playing online chess How do you avoid eye strain while playing online chess? I wear glasses that filters UV light, take a 5-minute break every hour, play on a large screen monitor (23 inch with a refresh rate of 60 Hz), and use lubricant eye drops twice a day. But I also believe that one of the big factor is that I don't blink enough while playing chess. My eyes are most of the time wide open, in order to avoid blundering. I would really appreciate your feedback, advice, and experiences to avoid such kind of problems.

Using Eye Drops (fake tears) can be useful when exceeding recommended screen time.
What also helps me is taking frequent breaks every hour and drinking plenty of water.


Where can I get a reliable and user-friendly, but not extravagant, chess clock? I'm looking for a reliable and user-friendly chess clock, but I don't want to spend $50 (under $25 would be preferable).  I'm not sure whether analog or digital would be better for me - so one question is: what are the pros and cons of each?  Also, if possible, I'd like it to show seconds, even for a couple-hour game.  If that's not possible, then at least for the last ten minutes or so.  What type or brand should I pay attention to?

Edit: I've found a couple clocks I'd probably be interested in - one is the cheapest analog clock I could find: a Chezmate precision quartz clock for $20.99, and the other is the cheapest digital one - for $32.90.  I'd like to know if the analog one will be all I'll need, or whether it'll be worth it to go for a digital one.  The digital one seems to have a few more features, but basically, in terms of durability and reliability, which would be better for the price?

I just saw you asked this couple of months back but adding my answer if others are looking for something in this price-range.

Do you have an iPhone? There are chess-clock apps which are pretty good. This is only for home games, as you don't want the other player scratching too much on your iPhone screen.

You should also search eBay. They are the best bet for low-prized yet pretty good digital chess clocks. Don't buy the cheap analog clocks as they have inherent problems and I have thrown away couple of them before switching to digital clocks. Always compare prices at Amazon before bidding on eBay.

Note: Digital clocks outweigh the cheap analog clocks by miles for under $25.

Pleasing displays
Lots of options for your game (e.g. extra seconds added for each move if you want it).
More lifetime than analog clocks at this price range (fewer mechanical problems).
Their only drawback is they need batteries.
Some digital clocks require little knowledge of how to set the clocks, but reading the manual helps and it is not very complicated.

Lots of good digital chess clocks on eBay (used/new; make sure it is listed as working) and Amazon. Good Luck.


Engine-invented variations/hypotheticals After watching a few alphaZero vs stockfish games, I was very intrigued. Clearly, engines can play at a different kind of level, but for the most part the openings seem pretty meta. Nothing extremely heretical jumped out at me in the first few moves. I dont know how much we humans can read into that; best case scenario the last few hundred years have modeled the opening permutations correctly if engines still use them. Still, engines crush humans on a regular basis.
Question
What would happen if we forced the engine to use a very absurd opening for the first few moves (like moving both rooks out) then have it resume against a human/GM?

I find watching the latest generation of self-taught AIs play is incredibly exciting - and of course they are relatively opaque as is much of AI these days.
Maybe openings turn out to be relatively tractable in that there are not so many fundamentally sensible options, given the transpositions which are possible. A player who begins with a few garbage moves however may still be able to utterly overwhelm a weaker adversary through superior midgame play. So the answer is it depends how much damage the AI inflicted on itself.
The midgame is where the real innovation of alpha zero seems to be. Particularly the received wisdom about pawn play has been turned on its head: pawn sacrifices can be powerful to win tempos and to clear space for line-moving pieces. Surely new concepts like this must already be a factor in top-level human analysis now.


Can someone describe a good/easy mental procedure to choose the best move here? This is kind of like magic to me. Once they show you it becomes obvious :) :(

Can someone point out a good/easy strategy that a player can mentally train/use to decide what is the best move here for black?

Note: Guys, there is a best move for black there can lead to a checkmate later. The goal is not to find it, but to come up with a procedure to find it so it can be applied to other positions.

I would say there are two tactical possibilities for black here:

1…Bxd3 2.Rxd3 Rxa4 3.Qxa4 Nxb2 wins the pawn back with a better position (the a3 pawn is now weak).
1…Rxe3 2.fe Nxe3 3.Qe2/d2 Bxd4 and the a4 Knight is hanging and the d1 rook is hanging with check … it still isn't over, in a game you should probably calculate further, but I'm to lazy to do that now.

There actually is an easy rule to find both of these tactical strikes:

Consider all captures!

Usually this rule is even broader: Consider all forcing moves! This includes captures, checks and attacks on stronger pieces.

Disclaimer: As with all rules this maxim has to be tempered by experience.


How many FIDE-rated games must be played to obtain a *non* provisional rating? I have a provisional FIDE rating of 1980 based on my score of 1 (two draws) out of 4 at a FIDE-rated tournament earlier this year; see: http://ratings.fide.com/card.phtml?event=2059100 where provisional rating is Rp.  I am playing in another FIDE-rated tournament next weekend and I seem to recall it may take as few as 9 games against FIDE-rated opponents to obtain an official (non provisional) rating, though I'm having a hard time authenticating this.

This is important to me as it's a 5-round tournament coming up and I want to know whether taking a bye may mean I have to play in yet another FIDE-rated tournament after this one to reach the plateau of 9, if that is indeed the correct figure.

Thanks in advance


World Computer Chess Championship: Why don't they run all computers on the same hardware? I was looking at the results of the 16th World Computer Chess Championship. You can see the hardware that the computer runs on. The reason why i'm asking this is that Mobile Chess engine is running on Nokia 6120c, right? It doesn't make sense.

Rybka runs on Cluster, 40 cores, if they ran Mobile chess engine on a Sumsung galaxy s4, it would probably have beaten Rybka. Am I reading the charts correctly? Because something definitely doesn't make sense, if I was a programmer going into a computer chess championship, Nokia 6120c would not be my weapon of choice.

Do they run all the engines on same hardware? Do they insure a fair game?

I think an historical look at that competition helps make the fact that each engine played on its own distinct hardware setup seem more reasonable. Don't think of it as merely an engine (software) competition, because it wasn't. Instead, think of it as a competition to determine the strongest chess-playing machine (hardware and software combined). And really this isn't so strange, especially given that this series of events dates back to an era when engines themselves were significantly weaker, computing power was more limited, and much less was known than today about how best to apply either hardware or software resources to the problem of computer chess.

Part of the challenge was of course just crafting better engines, regardless of hardware, but doing so in ways that took appropriate advantage of whatever particular hardware one could get a hold of was a significant part of the problem as well. Also (and this isn't a trivial point), these competitions in earlier days were as much (if perhaps not more) a way for hardware folks to show off as it was for engine developers. Consider two-time world champion Cray Blitz (1983, 1986). Its success wasn't just a feather in the cap of Bob Hyatt et al. for their ability to design a strong engine, but also a source of advertising for Cray Research's supercomputer and its ability to outstrip others at handling the calculating complexities of chess.

While I'm at it, for a more obvious example of how hardware was long just as prominent and distinguishing a part of the equation in computer chess, we can think back to Kasparov's 1996-7 matches against Deep(er) Blue, which wouldn't have happened at all (think sponsorship and such) if IBM wasn't eager to test and show off its hardware.

All that said, there is currently a well-known competition that offers what you want to see, which is a hardware-neutral comparison that's specifically designed to determine the strongest engine: Martin Thoresen's TCEC, which e.g. ChessBomb broadcasts when it gets played.


Can a King and Queen mate a King and Knight or is this a drawn game? White has a King and a Queen.
Black has a King and a Knight.

It is White's move. Can White win or is this ending a draw?

Without any pawns Queen vs Knight endgame is a theoretical win for the Queen.

Actually, most chess sites that have checkmates practice offer this very problem as one of them, along side many other classical ones such as Queen vs Rook, Two Bishops, etc.

Take a look at this mate problem in lichess

The same problem in chess.com

Here is an example of how you can win:

[FEN "8/8/3kn3/8/8/3KQ3/8/8 w - - 0 1"]

1. Kc4 Kd7 2. Qe5 Nc7 3. Qf6 Ne6 4. Kd5 Nc7+
5. Ke5 Nb5 6. Qb6 Nc7 7. Qb7 Kd8 8. Kd6 Ne8+
9. Kc6 Nc7 10. Qxc7+ Ke8 11. Qg7 Kd8 12. Qd7#


Tactical variations in the Caro-Kann? I am currently using the exchange variation of the Caro-Kann, so the:

[Title "Caro-Kann refutation"]
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1.e4 c6 2.d4 d5 3.exd5

I am looking for a more tactical approach. Is the fantasy variation worth it? Or are there more tactical variations?

The exchange variation, provided you continue with the Panov attack, is actually very tactical and aggressive. If you are looking for something quite different, I suggest what I play: the advance variation with an early h4 push.

That would be:

[StartPly "7"]
[FEN ""]

1. e4 c6 2. d4 d5 3. e5 Bf5 4. h4

on this website you can find some of the more common approaches to the variation. More than just a tactical sideline, it is extremely tricky, so you should know a few things before going into this mess. There are many lines where black has "only moves", but it is thought to not be very promising because in the end (after like 20 forced moves) black stands ok.

The thing is, most players who face this line have never seen it before, and they play the natural moves, falling into one of the hundred pitfalls available. An example is if black simply ignores h4 and plays 4. ... e6. After 5. g4, his bishop is trapped. This is only the first trap that you set (and on blitz, it's a very common one). Another one occurs after:

[StartPly "7"]
[FEN ""]

1. e4 c6 2. d4 d5 3. e5 Bf5 4. h4 h6 5. g4 Bh7 6. e6 fxe6 7. Bd3 Bxd3 8. Qxd3 Qd6 9. f4 Nd7 10. Nf3 O-O-O 11. Ne5 Nxe5 12. fxe5 Qd7 13. h5,

where black simply played normal moves to advance e5 and get rid of his doubled pawns, but in the end is playing without the three pieces of the kingside. I've played this line myself a couple of weeks ago, with devastating effect (I won on 20 moves, the idea is to simply double/triple on the f file).

This is just a few flavors of this sideline, check it out for yourself and see if the positions arising from it suit you.


Is there any software (preferably Linux) that, when managing a database, can inform you about opening transpositions? To make it simple, let's say that I play a game that opens with 1. e4 d5 2. d4.

I use Scid-vs-PC, and in this position, it just shows a bunch of games. Od course, if black plays now 2 ... e6, we transpose into the French defense, and suddenly thousands of games exist.

I'm looking for a software that after 1. e4 d5 2. d4 will show you the games that transpose to the French Defense.

I'm not sure if I'm explaining myself properly. So, just in case, this site has this feature that I'm attaching a picture of to show both cases in chesstempo

No.  It may implicitly 'know' internally but none of them explicitly tell you there is/are/couldbe transpositions.


Why are the symbols 0-0 and 0-0-0 used for castling in algebraic notation? I'm curious about why the symbols O-O and O-O-O  are used for castling in algebraic notation. Why not use the consistent and logical Kg1/Kc1 for White and Kg8/Kc8 for Black? Why adopt the less than obvious O-O and O-O-O from descriptive 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 up with it.

Allgaier (and algebraic notation in general) used digit-0. The use of letter-O is an anglo-saxon oddity.


Alphazero vs Stockfish Is the particular ending really a draw? Someone may try will FinalGen , please?
[Title "White to move"]
[fen "8/1B2k3/p7/P6p/1n1p2pP/6P1/4KP2/8 w - - 0 1"]

It's likely a draw. After going through a few lines (which strengthens the transposition table), Stockfish 11 at around depth 42 gave me 0.74 in the starting position. Especially in such a simplified endgame, this shouldn't be enough for White to claim a win. I also set it to White to move in the starting position.
Some variations I analyzed with Stockfish:
a) 1.Kd2 Kd6 2.Be4 Nc6 3.Bg6 Nxa5 4.Bxh5 Nc4+. Depth 38 gives 0.13, a clear draw.
b) 1.f3 gxf3+ 2.Kxf3 (2.Bxf3 Ke6 is 0.13, at depth 42) 2...Kd6 3.Kf4 Nc6: 0.13, depth 40.
c) 1.Be4 is the most challenging. Black should play 1...Kf6, and here White has a few tries:
c1) 2.Kd1 must be met with 2...Ke7!. After 3.Bg6 (3.Kc1 Kd6 4.Bg6 Ke7 5.Bxh5 Nd3+ is drawn: 0.25, depth 42) 3...Nc6 4.Bxh5 Ne5!, Black should hold: 0.38, depth 48. A more challenging move is 3.f3, but after 3...gxf3 4.Bxf3 Ke6 5.Bxh5 Nc6 6.Bg4+ Ke5 7.h5 (7.Bc8 Nxa5 8.Bxa6 Kf5 is theoretically drawn in the 7 piece tablebase) 7...Nxa5 8.h6 Kf6 9.Bh5 Nc4 10.g4 Ne3+ 11.Ke2 Nxg4, Black draws. Note that this 10...Ne3+ is extremely important - if Black couldn't play it with check, then White wins. This is why in variation c2 below, where White plays 2.Ke1 instead of 2.Kd1, 2...Ke7 will end up losing: this 10...Ne3+ resource no longer works.
c2) 2.Ke1 must instead be met with 2...Ke6!. Now 3.f3 can be met with 3...gxf3 4.Bxf3 Nd3+ 5.Kf1 Nc1 6.Bxh5 Nb3, which should be drawn, as Black is about to capture the a5-pawn. The 4...Nd3+ idea works nicely as its with tempo - in variation c1, this wouldn't have been the case as the White king was on d1. Another third move White can try here is 3.Bg6, and after 3...Ke7 4.Bxh5 Nd3+ 5.Ke2 Ne5, Black should draw - Stockfish gives 1.08 at depth 56, which shouldn't be quite enough to win. If White forces matters with 6.f3, then 6...gxf3+ 7.Bxf3 d3+ 8.Ke3 d2 9.Be2 Nc4+ 10.Kd3 Nxa5 11.Kxd2 is drawn in the 7 piece tablebase, as long as Black plays 11...Nc6 here.
c3) 2.f3 gxf3+ 3.Kxf3 Ke5 4.Bb7 Kf5 looks like it should be drawn.
c4) 2.Kd2 Ke7 3.Bg6 Nc6 4.Bxh5 Ne5 should be drawn (1.08, depth 55). Or 3.f3 gxf3 4.Bxf3 Ke6 5.Bxh5 Nc6 6.Bg4+ (6.Be2 Nxa5 7.Bxa6 is drawn in the tablebase) 6...Kf6 7.Bf3 Nxa5 8.h5, and here 8...Nc4+ or 8...Nb3+ both work, bringing the knight over to the centre/kingside with tempo. Yet another 3rd move is 3.Kc1, hoping to attack the knight with the White king. But after 3...Kd6 4.Kb2 (4.Bg6 Ke7 5.Bxh5 Nd3+ 6.Kd2 Ne5 should hold) 4...Nc6, the game is drawn.


Counting attackers and defenders, which pieces count? I've heard multiple times the idea of counting attackers and defenders in estimating whether an attack/sacrifice will succeed. However, I think authors are quite loose in counting who is the attacker and who is the defender. And their decision is heavily influenced IMO by the outcome, ie they'll include more attackers and discard more defenders if the attack succeeds.

For example, the game Karpov - Georgiev 1994, white to move. I think it's obvious that white's Q, B, Ne4, Re2 are attackers, but do Nf3 and Re1 count? For black, all pieces/pawns around K count, Ba8 doesn't. How about Rd8, Nd7 and Qb8?

bq1r1rk1/3n1pb1/1p1P2pp/2p5/P1B1N3/1Q3NP1/4RP1P/4R1K1 w - - 1 29

Edit: Source of the theory

Sokolov mentioned the theory in his book "Sacrifice and Initiative in Chess". On page 91

"However one theme that is repeated in almost all of these games is the attackers vs defenders ratio. Please keep this in mind! When you have an attack on a castled king and are planning to sacrifice a piece in order to destroy the opponent's defences, do a quick check on the number of your attacking forces vs your opponents defending forces. When you do this check, remember that as Steinitz already correctly claimed, the enemy king counts as a defender. Of course this theory does not always work, but it gives a very good initial indication of whether an attack may work."

So at least Steinitz and Sokolov had such theory, and I think Kasparov mentioned it as well.

First, I think you are looking for a hard-and-fast rule that does not exist since it really depends on the position. There still can be some guiding factors.

In the Karpov game above, which only lasted another 6 moves, it turns out that literally every white piece was an attacker, and was necessary for the attack to succeed, so the original question about whether Nf3 and Re1 were attackers, the answer was "yes", even if the Re1 was indirectly attacking by defending the other rook going to e8.

I would also say that it is not really related to a pure ratio. Sometimes, it can be a simple majority of one more attacker than there are defenders, and not all defenders are equal in every position. That said, if you have a 5 or 6 pieces bearing down on the opposing king position, and there are only one or two defenders, there is almost always going to be something there. You can safely go by instinct in such a case, even if you do not see your attack clearly all the way to the end.

For each position, when trying to figure this out, determining which pieces are attackers is usually not as hard as figuring out which ones are defenders. That is because, depending on the position, sometimes a pawn may be a defender, but other times it really is not, as in the Karpov game above f7 did nothing to defend. Also, you have to consider that the defending king also counts as a defender of itself: If you sacrifice so much material to the point that it is just your queen left, and there is no mate or win of material, the queen, just as in a pure K vs K+Q ending, cannot win without some support against the king it was attacking. You really have to judge what pieces can really help defend, and which ones only appear to be in the vicinity to help. Be especially aware when the opposing queen is way offside, and cannot get back to help. That alone, is often a deciding factor.

You also need to look at how pieces combine. For example, if you have a queen and knight attacking a castled black king with only the three pawns as cover, they can be very powerful with the knight on f5, and the queen on g5, and they might be able to go it alone. If it were instead a bishop on d3, and that same queen, then g6 might stop you cold without maybe many more attackers.

I also use this principle more when worrying about my own king safety rather than my opponents, but that is more that my positional style does not lend itself to attacking Morphy-style. It may also be because all-out attacks do not occur every game, but we always have to think about king safety.

  [Event "Tilburg"]
  [Site "Tilburg"]
  [Date "1994.??.??"]
  [Round "5"]
  [White "Karpov, Anatoly"]
  [Black "Georgiev, Kiril"]
  [Result "1-0"]
  [ECO "D58"]
  [WhiteElo "2780"]
  [BlackElo "2615"]
  [EventDate "1994.09.??"]
  [FEN ""]

  1. d4 Nf6 2. c4 e6 3. Nf3 d5 4. Nc3 Be7 5. Bg5 h6 6. Bh4 O-O 7. e3 b6 8. Be2 Bb7 9. Bxf6 Bxf6 10. cxd5 exd5 11. b4 c6 12. O-O Qd6 13. Qb3 Nd7 14. Rfe1 Be7 15. Rab1 a5 16. bxa5 Rxa5 17. a4 Re8 18. Bf1 Bf8 19. Qc2 g6 20. e4 dxe4 21. Nxe4 Qf4 22. Bc4 Bg7 23. Re2 c5 24. d5 Raa8 25. Rbe1 Rad8 26. Qb3 Ba8 27. g3 Qb8 28. d6 Rf8 29. Bxf7+ Rxf7 30. Neg5 hxg5 31. Nxg5 Rdf8 32. Re8 Qxd6 33. Qxf7+ Kh8 34. Ne6 1-0


When capturing en passant, is a position possible such that there is a pin over the square of the taken pawn, rather than the taking pawn? I am trying to write a simple chess program, and as part of this I am writing methods to find all valid moves. I can detect pins and have no trouble leaving out the moves that would result in the moving player being in check, except for one situation I am not sure about.

After an en passant capture, not only is the square previously occupied by the capturing pawn now vacant, but so is the square of the captured pawn. Is there any position at all where capturing en passant results in a discovered check on the king of the player that is capturing en passant, not because the capturing pawn was pinned, but because the check was previously stopped by the captured pawn?

I think this situation is simply not possible, at the very least I can't think of a position and series of moves that results in this situation; the fact that you have to capture en passant at the first opportunity means that either the pawn that should later capture en passant is pinned and can't advance to the fifth rank, or the check is blocked by a different piece anyway. Unfortunately I am having trouble ruling out there is some counter-intuitive position where this might happen. Could someone confirm my suspicions (or provide a counter-example)?

Really interesting question. I think the following shows that such a situation is sort of possible, depending on how you define the pin.
[StartFlipped "0"]
[FEN "7k/4p3/8/2KP3r/8/8/8/8 b - - 0 1"]

1... e5 2. dxe6?! {Illegal move!}

Now, 2. dxe6 is illegal. The check would go from being stopped by both pawns, to being stopped by neither.


How to convert PGN moves to long algebraic notation (in python)? I want to read a PGN file and then advance to a certain move number, and feed that to an UCI engine.  Turns out engines work using long algebraic notation, and PGNs are in short algebraic.  What is an easy way to make the conversion?  i.e. from SAN to LAN.

I realize that generating long algebraic notation requires knowledge of the board state & chess rules, so I don't want to write it all again!  Surely something like this must already exist - either a command line program or a module (preferably in python).

Would this be what you are looking for? PGN-extract (A command line utility)
http://www.cs.kent.ac.uk/people/staff/djb/pgn-extract/

I can see a flag in the feature doc that might help:

-W[cm|epd|halg|lalg|elalg|san|uci] - specify the output format to use
-Whalg is hyphenated long algebraic.
-Wlalg is long algebraic
-Welalg[PNBRQK] is enhanced long algebraic. Use the characters PNBRQK for language


What is the idea of the Kaufmann Attack (5.c4) against the Petroff? What is the idea of White playing  1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. c4 ? Does he intend to get some good version of the main lines, while avoiding certain sidelines? It seems in fashion now with games like this one, but I am not sure I grasp the full concept - Ian Nepomniachtchi vs Sanan Sjugirov, 2016

In the main line 5.d4, black responds with 5....d5 in order to occupy the centre and to continue his development. The most popular line continues with: 6.Bd3 Be7 7.0-0 Nc6! 8.c4 Nb4! 9.Be2 0-0 (e.g. Nakamura-Akobian). Important to note: after 7....0-0 white has good chances to obtain an advantage after 8.c4.

With 5.c4 white wants to discourage black to play ...d5. After 5....d5 white seems to obtain an advantage with 6.Nc3. 6....Nxc3 is very dubious: 7.dxc3 Be6 8.Ng5 with a big advantage for white.
Instead, black often plays 5....Be7. After 6.d4 0-0 7.Bd3 d5 8.0-0 white has successfully transposed to 5.d4 d5 6.Bd3 Be7 7.0-0 0-0 8.c4 (Nepomniachtchi-Wang Hao (blitz)).

However, black has better alternatives after 5.c4, for example:

5....Nc6 (Nisipeanu-Giri) 6.d4 d5
5....Be7 6.d4 Nc6 7.Bd3 Ng5

      [StartPly "8"]

      [FEN ""]
      1.e4 e5 2.Nf3 Nf6 3.Nxe5 d6 4.Nf3 Nxe4 5.c4 (5.d4 d5 6.Bd3 Be7 7.O-O Nc6 (7...O-O 8.c4) 8.c4 Nb4 9.Be2 O-O) 5...Be7 (5...d5 6.Nc3 Nxc3 7.dxc3 Be6 8.Ng5)(5...Nc6 6.d4 d5) 6.d4 Nc6 (6...O-O 7.Bd3 d5 8.O-O) 7.Bd3 Ng5


Simple chess variants for beginners How suitable would these variants for beginning players?

First to check wins
Three-Check Chess
First to take king wins

All other rules being equal.

First of all, I think the question is largely opinion based. However, I'll try to answer from my own experience about the X-check variants, as some matters about the chess variants can be described and judged objectively. If you are asking whether the variants are suitable to be taught to beginners (in terms of rule simplicity), then sure, they are. If you are asking whether or not they would benefit the beginners by improving their normal chess play, then I'd say no - they would only give them wrong ideas and confuse them.

My reasoning for the statement above is, that the "first to X checks" variants employ opening theory and tactics completely different from normal chess; very few ideas from these variants can be taken over to normal chess. For instance, one of normal opening play ideas (dominate the center with pawns) seems to perform very poorly in the X-check games, as it puts the king in danger of checks. There are many situations where a single bad move very early on in the opening leads to a forced loss (see for example the wiki article you linked; this is also akin to losers chess). Thus, in order to survive, one must employ strange pawn structures, completely unsuitable for normal chess. Additionally, one often sacrifices piece(s) just to get that check in - again, not really applicable to normal chess. In normal chess, such sacrifices are useless, unless they lead to a forced win/advantage, whereas in X-check chess, you have to defend against them, as each one brings the rival closer to victory.

The third variant, as BlindKungFuMaster noted, is basically normal chess. I'd recommend to keep it simple in the beginning, just do normal chess. Try chess variants only after learning the basic concepts and good practices of normal chess - then it is interesting to compare how they do or do not work in the variants.


Petrov Defense, 8...Bg4 easy equality for Black? When I analyze the 8...Bg4 Petrov it always seems like Black gets an easy equality. For example:

Garry Kasparov - Patrick G. Wolff
New York/London simultaneous 1984

1. e4 e5 2. Nf3 Nf6 3. Nxe5 d6 4. Nf3 Nxe4 5. d4 d5 6. Bd3 Be7 7. O-O Nc6 8.
Re1 Bg4 9. c4
   9. c3 f5 10. h3
      (a) 10. Qb3 Rb8 11. Nfd2 Bh5 12. Nf1 (12. f3 Nxd2
13. Nxd2 O-O 14. Qc2) 12... O-O 13. Ne3 Nxf2 =
      (b) 10. Qc2 O-O 11. Nfd2 Bd6 =+
      (c) 10. Nbd2 O-O =
   10... Bh5 11. Qb3 Rb8 =
   9. Bxe4 dxe4 10. Rxe4 Bxf3 11.Qxf3 Nxd4 12. Qd3 Ne6 =
9... Nf6 10. cxd5 (10. Nc3 Bxf3 11. Qxf3 Nxd4 12.
Qg3 dxc4 13. Bxc4 O-O 14. Bg5=) 10... Bxf3 11. Qxf3 Qxd5 12. Qg3 !? (12. Qxd5
Nxd5 13. Nc3 Ndb4 14. Be4 Nxd4 15. Be3 Ndc2 16. a3 Nxa1 17. axb4 Nb3 18. Bd5
O-O 19. Bxb3 Bxb4 20. Rc1 $11) 12... Qxd4 13. Nc3 O-O =+

Kasparov ended up outplaying Wolff in the middlegame, but out of the opening Wolff was at least equal. All the other lines seem to quickly end in equality as well.

Is playing 3.d4 the only try for an advantage in the Petrov?

No, it is not "easy equality". It is "complex fight where Black has good chances for equality, with theoretical debate still going on".

Anyway, 3.d4 won't be the only try for an advantage in the Petrov. 3.Nxe5 is still the main field where White looks for advantage. He can deviate from this game Kasparov-Wolff in several ways, including 5.Qe2 (recently renewed by Carlsen and Kramnik), 5.Nc3 (the main try for an imbalanced position, see Karjakin-Caruana, 1-0, in this year's Candidate tournament), or later 8.c4 (a lot of heavy-weight fights involving Anand, Kramnik, Leko or Naiditsch in the 2000-decade).


What is the difference playing against human vs chess engine? I have been playing with chess engines for over a year now at extreme difficulty levels. I never played a single game with a human player. I am worried that when i face humans in a tournament, my chess thinking must be completely different and i might not survive.

Does playing against chess engines improve your ability better than against human players? What do you think?

There are two separate problems with your trainingspartner: Strength and style.

Generally you improve the most if you play against opponents slightly stronger than you. You have to adapt by upping your game, but you are still able to adapt! If you are always crushed you only learn to be solid at all costs. You can see this a lot if teenage prodigies play too early against world class opposition: Their game dries out. They systematically unlearn all creative impulses, because every risk taking is punished.
If you play against engines that always beat you, their style doesn't really matter. But if you would play against an engine only slightly stronger than you (which would be a better choice), you would experience the problem, that you adapt to their particular style. Which usually means you get very good at sniffing out tactical pitfalls, but your positional understanding will stay underdeveloped. I know this very well because I played for two years almost daily against a Mephisto board computer before I joined a chess club and it took me many years to stop losing against human opponents who were far weaker tactically.


Playing Crazyhouse OTB I was playing Crazyhouse online on Lichess and I wondered how to play OTB, namely how to change the color of a captured piece.
I came up with 2 methods.

Exchange the captured piece for another of a separate chess set, picking the opposite color.

Pieces are 2d cards, with the Black version of the piece on one side and White on the other.]3

Does anyone know better methods?

Shogi also called "Japanese Chess" use the crazyhouse mechanics as well. They have one-colored  (flat) pieces that always face in one direction. If you capture a piece and bring it back into play you just let it face towards your opponent.


What opening is recommended if white is only playing for a draw? If in a tournament game, white is only aiming for a draw, what openings and strategies will be recommended for him? I guess that the answer may depend on the following different mindset for black:

Black is happy with a draw as well.
Black would love to win but can accept a draw.
Black must win.

I am aware of a related question but my questions seems to be different.

The English Opening (1.c4) is excellent for pushing for a drawish line. There's not many risky/sharp lines in it.

The Reti Opening (1.Nf3) is also a good "safe" opening without too  many sharp lines.

In both of these, flexibility is key.

These delay committing to either "wing pressure" with minor pieces or "center occupation" with pawns; white can adapt to whatever black throws out and slow things down, whether black wants to win or is looking for a draw themselves.

If black is looking for a win, the French Opening might be a possibility - most lines are fairly defensive (not all - some are very sharp and should be avoided by white) and can push said player into being so aggressive as to make a mistake that could even hand white an easy win.

Note: (suggested by @ATLPoly)

With both the Reti and the English, it is possible to play sharply with moves like f5. These aren't the best lines for black, but be warned that they are sharp and do require white (and black to a greater extent) to play accurately, even though the position is slightly in white's favor.


Why is the engine suggesting this move? [FEN "r1bqk1nr/p1ppbppp/1p6/n2P4/8/2N5/PPP1QPPP/R1B1KBNR w KQkq - 3 7"]

1. g4

With White to move, the Lichess engine suggests g4 in this position. Can someone explain why it's a good move?

Black would like to continue their development with Nf6 and castling short. g4 discourages Nf6; after g5, the knight is forced back. It also prepares Bg2, which protects d5 without giving up the pin on the e-file. The weakening of the kingside apparently isn't too much of a problem; Black isn't developed enough to take advantage of this, and White can always castle queenside.


Why aren't 1.e4 g6 2.d4 Bh6, and 1.e4 b6 2.d4 Ba6 considered by theory? As the title above, why aren't 1.e4 g6 2.d4 Bh6, and 1.e4 b6 2.d4 Ba6 (or eventually beginning with 1.d4) for Black not even considered by theory? Isn't the eventual early trade-off of White's strong Bc1 and Bf1 for Black's Bishop an asset for Black? What is the best reply for White vs such irregular defences? Should he trade the Bishops or avoid that? (i.e. with f2-f4 and c2-c4)?

White should trade bishops and use the unprotected knight to gain some extra tempo and gain a massive lead in development, e.g.

[FEN ""]

1. e4 g6 2. d4 Bh6 3. Bxh6 Nxh6 4. Qd2 Ng8 5. Nc3

4... Ng4 is best met by 5. h3 Nf6 (forced) 6. e5 Nd5 7. c4 Nb6 8. Qh6 and Black has problems completing his development, though there is no forced win at the moment.

I haven't analyzed the b6/Ba6 lines but I guess a similar concept holds.


Starting with the Sodium Attack Can someone suggest good to great developments starting with the Sodium Attack Na3? I am currently using this opening for my games, but I cannot find a really powerful strategic development with this opening. Any previous games with this is also welcome, as well as some advice on development strategies.

The analysis below is without the aid of a computer or any resources, but are just my thoughts on an unconventional opening:

[FEN ""]

1. Na3 e5 {Black seizes the centre and has the option to play ...Bxa3} 2. b3 {White dissuades ...Bxa3 and plans to fianchetto the bishop later} d5 {Black gains more space to counter white's hypermodern plans} 3. c4 {White must challenge the black centre, and hopes for 3...dxc4 4. Nxc4} d4 {Black wants to retain the space advantage} 4. Nc2 {Preparing e3, Be2 and O-O} Nf6 5. Nf3 Nc6 6. d3


How should I play against the Philidor defense? As white, I often encounter the Philidor Defense by black:

[FEN ""]

1. e4 e5
2. Nf3 d6

I usually play Nc3 or d4 on the next move, but is this the best move? What are some lines (advantages or disadvantages) against the Philidor?

3. d4 is the usual move after 1. e4 e5 2. Nf3 d6.  Chess Opening Theory states that it is probably the best move, and also concedes 3. Bc4:

The best move is probably 3. d4. White threatens a queen exchange with dxe5 dxe5 Qxd8+ Kxd8 and Black can forget about castling. It puts pressure on the center and the Black fortress may collapse at any time.
Another possibility is 3. Bc4 leading to a more positional game, playable for both camps.

Fred Reinfeld suggests the following line (exclamation marks are his) as in this game.  White maintains a sharp edge:
[FEN ""]
1. e4 e5 2. Nf3 d6 3.d4 exd4 4. Qxd4! Nc6 5. Bb5! Bd7 6. Bxc6 Bxc6 7. Nc3 Nf6 8. Bg5 Be7 9. O-O-O

A good resource to study would be shredderchess.com's opening database.


Is there a hash or string that represents a stockfish evaluation of a position to a certain depth? Is there a hash or string that represents a stockfish evaluation of a position to a certain depth?  For example for a given FEN, can you analyze to a depth of say 10 and get a hash to represent that position AND depth of analysis?  That would allow you to come back later and, if wanted, continue analysis to a greater depth at a later point.

I doubt that can be possible.

An analysis to a certain depth contains the generated position tree and the calculated values, which is quickly becoming a very large amount of data.
For depth 10, you probably need several megabytes of memory to represent the analysis result in a way that it could be used to continue searching deeper. There is simply no way to compress this into a small hash or anything else.


Ancient style chess games? I know there are some really old games on the internet there , but are there records of any really good/great games played in the ancient style of chess ?

This style had rules like pawns could move only one square at a time.
Rook's pawn promotion would be a rook , bishop's pawn would be bishop etc.

TL;DR: there are recorded games for Shatranj from the 10th century onward, but I haven't found the variant asked for by the OP.

The earliest recorded game of modern chess was 1475:

  1475: Castellvi-Vinoles, Valencia 1475. The first documented chess game played with the modern queen and bishop moves; the moves were described in the poem Scachs d'amor.

Source: wikipedia

Going to the predecessor of modern chess we have Shatranj:

  The earliest listing of works on chess [Shatranj] is in the Fihrist, a general bibliography produced in 377 AH (988 AD) by Ibn al-Nadim. It includes an entire section on the topic of chess.

Source: wikipedia

chess2u.com provides, what they claim to be, the oldest recorded chess game (10th century):

  f3 f6 2. f4 f5 3. Nf3 Nf6 4. g3 g6 5. Rg1 Rg8 6. h3 h6 7. e3 e6 8. g4 fxg4 9. hxg4 g5 10. fxg5 hxg5 11. d3 d6 12. e4 e5 13. Be3 Be6 14. Nxg5 Ke7 15. c3 Nxg4 16. Ke2 c6 17. d4 d5 18. b3 b6 19. Nd2 Nd7 20. Qc2 Qc7 21. Qd3 Qd6 22. Ndf3 Ndf6 23. Bh3 Bh6 24. Bf5 Bf4 25. Rac1 a6 26. c4 Rac8 27. c5 bxc5 28. Bxc5 Ke8 29. dxe5 Nxe5 30. Nxe6 Rxg1 31. Rxg1 Nxf3 32. Kxf3 1-0 (Black resigns)

However I haven't found any sources for the variant you mention.


What to do with space? I sometimes find that after an opening, I have created "space" for myself, and control most of the board. But then I'm not sure what to do next.
For instance (0 6 time control on Lichess, me 1560 vs 1400):
[FEN ""]
[StartPly "25"]

1. d4 e6 2. c4 c6 3. Nc3 d5 { D31 Semi-Slav Defense: Accelerated Move Order } 4. c5 Bd7 5. Nf3 Nf6 6. Bg5 Be7 7. Bxf6 Bxf6 8. e4 dxe4 9. Nxe4 Be7 10. Bd3 b6 11. b4 bxc5 12. bxc5 Bc8 13. Qd2 Ba6 14. Bxa6 Nxa6 15. O-O Qc7 16. Qd3 Nb8 17. Nfg5 Nd7 18. Nf3 Rb8 19. Neg5 h6 20. Ne4 O-O 21. Rab1 Rxb1 22. Rxb1 Rb8 23. Rxb8+ Qxb8 24. Qc2 Qb5 25. h3 Nf6 26. Nd6 Bxd6 27. cxd6 Qd5 28. Qc5 Qxc5 29. dxc5 Nd7 30. Nd4 Kf8 31. Nxc6 Nxc5 32. Nxa7 Ke8 33. Nb5 Kd7 34. Kf1 Nb7 35. Ke2 Nxd6 36. Nxd6 Kxd6 37. Kd3 Kc5 38. Kc3 Kb5 39. Kb3 f6 40. a4+ Ka5 41. f3 g6 42. Kc4 Kxa4 43. Kc5 e5 44. Kd5 Kb4 45. Ke6 f5 46. Kxe5 Kc5 47. Kf6 g5 48. Kxf5 Kd5 49. Kg6 Ke5 50. Kxh6 Kf4 51. Kh5 Kg3 52. Kxg5 Kxg2 53. f4 Kxh3 54. f5 { Black resigns. } 1-0

I'm equal on material, ahead on development, and I control much more of the board.
How do I convert these advantages into something concrete?

Having a space advantage means you have more room to navigate your pieces.
Space may allow you to attack on both sides of the board, or attack on one side then switch to the other;  the cramped defender simple can't navigate as well.
You may be able to dominate an open file as it is easier for you to double or triple heavy pieces.
In late middlegame to endgame situations your king can get further up the board.
In your specific game black has a lot of weak squares and is behind in development as well as space disadvantaged.  Your play needs to consider other fundamental elements.  First after 13...Ba6 you shouldn't waste time with 14.Bxa6 which after Nxa6 allows Nc7-d5 with occupation of an outpost.  But rather just continue development with 14.0-0
In the game black continued to play horribly with 15...Qc7 and after 16.Qd3 Nb8 you have various options.  Doubling rooks on the b-file and penetrating the 7th rank will be crushing.  Consider the rook lift Rb1-b3 -- if Black castles trying to get his h8 rook in the fight, the b3 rook can swing to the kingside.
You can also think about occupying d6 with a knight (Ne5-c4-d6).
Wasting time with Ng5 and back like you did is not because you don't know what to do with space, but rather you don't know what to do with your pieces in general.
Target weak squares, coordinate, and invade!


How many sensible games of chess are there? Analytic procedures for estimating the number of possible games of chess typically reason that on each ply, a player has some limited number of sensible options, O, and the average game of chess lasts about p plys. Thus, there are about O^p games of chess. Choosing O=3 and p=80, you get something like 1.5x10^38. This is the strategy taken by Shannon and others.
However, such procedures are likely to mis-estimate the true number of sensible games. Chess games are frequently characterized by long sequences of forcing moves, where there is only one option worth considering. Further, the estimated number of options for each ply seems pulled out of thin air. Thus, the true number of decision points is different than assumed.
What is a better estimate?

TLDR: Forced plies are relatively rare, and when given an option, a player tends to have more options than supposed by the example calculation. Using the methodology below, I estimate that there are about 74 unforced plies in a game of chess and that a player has about 4.35 sensible options on each one. Thus, the number of sensible chess games is 4.35^74 = 2.37x10^47. Note that this is much larger than the analytic estimate in the question, roughly 1.5 billion times larger!
Methodology and data
The following procedure is based on the assumption that if a given ply is sensible, then we should observe it given a large enough sample of games. If it is not sensible, then it would never be made, and hence would never be observed.
First, I downloaded the Lichess Elite database. This is a database of non-Bullet games played on Lichess by players with ratings of +2200. Note that the actual selection criteria are a bit more complicated. The point is that these are fairly expert players, who presumably are unlikely to make silly errors. There are 3,818,709 games in the database, of which ~99.8% are unique. The average game is 84 plys long, and the median is 80.
4 million games is too many to feasibly process, so I randomly sampled 100,000 for further analysis.
From this data, I constructed a tree representing all observed games. At the root of the tree is a single node representing the start of the game. The children of this node represent all observed first plies. Each child in turn has its own children, representing all observed replies to the first ply, and so on and so forth. When a game is terminated, then the last ply made has a single child denoting the number of observed games that arrive at that game state. I also pruned the tree, so that if some node is associated with only a single continuing game, I cut it out so that it only is associated a single, terminating node.
Finally, I marked whether each ply was forcing or not. A ply was forcing if (i) there was only one observed reply, and (ii) more than one game reached that ply.
A few notes about the data:

There are 207,635 unique game states in the tree. This is a slight overestimate, as it doesn't take into account transpositions.
Over half of them, or 107,833, have been visited by more than one game.
10,630 of the nodes, or roughly 10%, have been visited by more than 10 games.
Forcing is confounded with game depth. As we go further in the tree, fewer and fewer games are associated with each node. Thus, for some node deep in the tree, it may be that there were more sensible moves to make, but we just didn't play that game enough times to find them. To deal with this, I will only be looking at nodes that were reached by at least 10 games.
The above considerations mean that our look at the end game is dim. I don't have good intuitions on this point, as it could seem reasonable to suppose that endgames are characterized by more, fewer, or the same number of forced plys. More of the board is open to make slightly different moves, but the probability of a forcing check is presumably higher.

Results
For plies with more than 10 associated games, the average number of observed replies is 3.95. Omitting non-forcing moves, this increases to 4.35 replies. These numbers did not vary by player color.
Of the nodes with more than 10 associated games, 11.67% of them are forcing. Captures and checks are more likely to be forcing: a capture was forcing 30.4% of the time vs 0.09% for non-capturing moves. Similarly, 38.6% of checks were forcing, vs 11.3% of non-checks. Neither White nor Black were more likely than the other to make a forcing move.
As shown in the following figure, the number of available options changes over the course of a game. In the opening, players are free to make any choice they wish. Indeed, of the 400 possible opening moves, most (288) of them were observed at least once, and 139 of them were observed at least 10 times. Later, players are gradually more restricted, until they have about 2.5 options per ply.

Breaking it down by captures and non-captures is illuminating. The following figure displays the proportion of plies that are forcing, broken down by whether or not they were a capture.

Similarly with checks and non-checks:

Conclusions
Forcing moves are relatively rare, and that players tend to have many sensible options for any given reply. Thus, there are more sensible games of chess than purely analytic methods would indicate.


How do age and initial rating correlate to decline in playing strength with age? The current Rausis phone cheating scandal saw a player with an initial rating of about 2500 in his 50's improve by about 200 rating points in 6 years. This improvement was remarkable because older players are expected to get weaker with age.

It even received attention a couple of week's ago, before the scandal broke, with the suggestion that he was hacking the system by playing mostly much weaker players and taking advantage of the 400 point rule.

Has there been any analysis showing the correlation between age and rating on one hand with expected decline on the other?

For example, I'm in my 60's and my FIDE rating is about 1700. How much decline can I expect in the next 10 years? Would that be much different for a 2200 master in his 60's? For a 2500 GM? For 1500 player?

There is a chess.com blog article which looks at the data for just one month which is unsatisfactory in many ways. It shows a graph of average rating in 5 year bands but with no analysis following players with similar starting ages and ratings to see what the decline is over a given period.

The data is there. FIDE publish more than 18 years of rating data which is available for download. Olimpbase have data available for download going back another 30 years although then only strong (master level) players had ratings.

I looked at the data briefly and got some interesting conclusions.

I used data from FIDE webpage for january in years 2006-2019.

I calculated each player's rating change in consecutive years and used player's age in the first of the two as the age when this rating change occurred. Then I simply calculated the average. The result is this:

As you can see, players are on average gaining rating only until the age of 27, and afterwards they tend to slowly lose rating. Children gain the most rating per year, which is very intuitive.

Rating range 19-90 from up close:

Rating loss increase looks linear.

Cumulative rating change:

This is of course cumulative change since the age of 10.

Secondly, I did the same thing but separated players into groups. I looked at each of their entry in the data and put them into respective categories according to the maximum rating achieved in it: which might not be their actual peak rating, but should be a good indication of their top strength.

Gains are much larger here. Might be due to the fact that the negative contribution of sub-1500 players isn't included. Intuitively, higher rated players have higher average rating gains, but the decline rate seems to be similar regardless of the strength.

The linear range up close.

Cumulative again.


What is the difference between an opening and a defence? I would like to know why some openings are called "defences" and other all called "openings." What is the difference?

"The opening", in general, is the first phase of a game of chess, in which both sides develop their pieces. It is followed by "the middlegame" and, if the game gets that far, "the endgame".

When people talk about "an opening", they are referring to a particular series of opening moves that has a name. For example, 1.d4 d5 2.c4 e6 is the Queen's Gambit Declined, and 1.d4 d5 2.c4 dxc4 is the Queen's Gambit Accepted.

Openings that are defined by the moves that Black makes are often called "defenses", since White is generally considered the attacker and Black the defender by default. For example, 1.e4 c5 is the Sicilian Defense and 1.e4 e6 is the French Defense.


Browser based FICS client: exists or may I build one? I am planning to build an open source web based client for FICS. I enjoy playing at http://chess.com, but don't like the fact that it is a closed service. So, I need something similar, but for FICS.

What I am wondering about is, if something already exists for this. Wouldn't want to end up with duplicated effort.

Also, is it something that the chess community would use? What is the most popular way that people connect to FICS?

Mobialia is a decent modern FICS client that works on the browser.


Why did Carlsen play 7. dxc5 in Game 7 of the 2018 World Championship? As a class A player, I have some understanding of opening principles. Relevant to the move played in the game, I know that it's advantageous to control the center, to have central pawns controlling the center, and to maintain tension for as long as possible. It's for these reasons that I was confused by 7. dxc5 in game 7 of the world championship.

I would understand this move if Carlsen followed it with 8. cxd5, giving black an isolated queen pawn and trying to play against this for an advantage. But Carlsen did not follow up with this idea, and I was unable to understand the strategy of his next moves.

What's the idea behind 7. dxc5 in this game? Why give up a central pawn and break tension? Here's a link to the game where it can be replayed: Chessbase.

The same move order also occurred in game 2 (at least up to 9...Qa5). It's a good question that you're asking, though I'm afraid there's no intuitive answer in the way that you're looking for. Instead, these are very concrete lines well polished by computer analysis, which means the best way to understand a decision such as 7.dxc5 is to simply play through the lines a bit, and consider a couple of alternatives in order to draw close analogy between these QGD lines and pinpoint the main differences with and without dxc5.

That said, part of the answer also simply lies in the strategies that the players have adopted in this match (which ultimately stems from their exact preparations), e.g., Caruana seems to favour these rather more solid lines with 4...Be7 as opposed to the somewhat sharper variations such as the Vienna (4...dxc4), Tarrasch (4...c5) or Ragozin (4...Bb4) to name a few, most of which by the way Caruana has himself played previously. But then 4...Be7 essentially allows Carlsen to stay in the mainline theory of QGD with Bf4 and e3..., and from Caruana's point of view, it's the 6...c5 variation that he seems to have chosen to prepare for and play in this match against this line (so you should remember the line as Be7... c5, as the key defining moves of this variation), which he has followed similarly in both games with this Nc6 and Qa5-Rd8 or Qa5-Qd8 ideas.

Now here's my attempt to offer you a bit of intuition for the specific 7.dxc5 variation, but do take it with a grain of salt as these (like most other Queens pawn openings) are inherently very concrete lines after all: (annotations added to all variations and sub-variations)

 [title "London WCC2018 7.dxc5 in QGD games 2&7"]
 [fen "rnbq1rk1/pp2bppp/4pn2/2pp4/2PP1B2/2N1PN2/PP3PPP/R2QKB1R w KQ - 0 7"]

 7. dxc5 {What it achieves in short: i. leaves the bishop slightly misplaced on c5, often it has to return to e7 again e.g. to reroute to f6, or to side-step a3-b4 ideas. ii. prevents black from taking on d4 which would further enable black's development as white is essentially forced to recapture with a piece. On the same token, it keeps the knight on f3 where it is well placed controlling e5 and ready to re-route via d2 if needed. iii. Semi-opens the d-file with ideas to quickly play Qc2 Rd1 with immediate pressure along d-file, where d5 pawn still stands.} Bxc5 (7. Be2 {Let's make a quiet move and see what happens if we let black take on d4} cxd4 8. Nxd4 (8. exd4 dxc4 9. Bxc4 b6 {One line among others after exd4. But it already exemplifies why exd4 is bad for white: to play for any edge white has to maintain their IQP but black gets then an easy development with early b6 Bb7, target on d4 and a somewhat misplaced bishop on c4 which can be exploited to gain tempo. If white decided to resolve the IQP immediately it would lead to a completely liquidation of most pieces ending in a completely equal game.}) Nc6 {Thanks to the knight on d4 the Nc6 move comes somewhat with a bit of tempo as it forces white to react:} 9. Nxc6 bxc6 {and black has a solid grip over the centre, and partly solved their bad c8 bishop problem as now there are ideas to trade via a6, that is, Qa5 Ba6 ...} (9. Nf3 Qa5 {or dxc4, and black even has a slight initiative, Nf3 back is clear tempo given up by white.})) 8. Qc2 {As opposed to the more fashionable lines, namely cxd5. Qc2 side-steps the d-file to avoid queen trades and free the file for a quick rook move. Prophylactically stops Bf5 in certain lines because white will be ready to face it with Bd3, e.g. after Qa5 Re8 e5 Nd4 Bf5. It also controls e4 stopping any possible early Ne4 by black, and avoids immediate material trade that is common to cxd5. Finally, it also x-rays the bishop on c5 which is unprotected, forcing black to react to the potential discovery attack.} (8. cxd5 {still rather famous line, previously played by many including Carlsen, MVL, Grischuk, Caruana.} Nxd5 9. Nxd5 exd5 10. Bd3 Bb4+ 11. Nd2 {10. a3 also possible. And black is fine structurally because even the IQP is not permanent as d4 is playable in many lines that follow. But black has a somewhat slow play, because bishop is misplaced on b4, often it reroutes to f6-b2 diagonal via e7, and black still has to play Nc6 and develop c8 bishop. So it's decent for white but more committal which is maybe why Carlsen is not opting for it.}) Nc6 9. a3 {Still a highly theoretical line, still evolving as Carlsen and Caruana have been showing in the match so far, but it's one that suits both their styles of having a closed positional QGD game, with various continuation choices left for both sides.}

Hopefully, the above analysis (by no means exhaustive) offers you a glimpse of the kinds of ideas that underlie the dxc5 line. But bear in mind that, in general, to answer such questions for yourself, try to uncover not only the concrete aspects of what the move achieves, but also the sorts of ideas it prevents or side-steps.


What's the meaning of "%evp" in a PGN comment? Example:

{[%evp 0,17,14,14,14,-25,-15,-15,7,7,55,48,48,48,472,228,802,802,804,771]}
1. e4 e5 2. f4 exf4 3. Bc4 Qh4+ 4. Kf1 Bc5 5. d4 Bb6 6. Nf3 Qg4

What's the meaning of these numbers when used together with %evp?

A similar question was asked by GM Tony Kosten on the chesspub forum back in January:

  Looking at the last set of PGN files I received, at the beginning is a
  new tag followed by lots of numbers, like:

  {[%evp
  0,96,30,30,22,1,30,2,2,-9,-3,-44,23,23,21,32,41,37,44,23,22,18,26,11,22,
  -4,0,-1,8,7,7,14,9,5,16,8,38,16,22,19,25,54,19,19,22,22,22,20,20,20,24,-18,24,
  -53,-53,-61,-61,-56,-23,-20,41,41,39,39,35,30,44,44,33,50,70,70,75,75,75,75,75,
  56,60,59,62,56,68,56,50,48,48,40,46,60,49,30,48,47,47,59,46,56,57]}

  I assume ChessBase 15 generates this when it quickly analyses games
  when you open them. However, is this a standard PGN code, can other
  chess programs read it?

The original PGN standard was created and published in 1994 by Stephen J Edwards. Here is a copy of his original standard: Portable Game Notation Specification and Implementation Guide. By 2001 he had dropped out of the project when this supplement was published to the PGN standard. There it defined a new embedded command string which would be marked by a starting "[%".

  3.2 A generalised format for embedding commands in comments.
  3.2.1 Position
  An embedded  command may occur at any position in a standard PGN comment, ie  between { } . For example: {Optional leading
  comments [%clk 1:05:23] optional trailing comments} where  [%clk
  1:05:23]  is the embedded command string.

  3.2.2 Structure The command string is structured as follows.

  A leading tag of [% A command name consisting of one or more
  alphanumeric characters. A space character. Either a single parameter
  or a comma delimited list of parameter values. A closing tag of ]

So, "[%evp" is an embedded command, first seen in Chessbase 15 output. As such it is Chessbase 15-specific until such time as Chessbase publish how they use it, at which time other pgn producers/consumers can start using it too.

My speculation, FWIW, is that it is part of Chessbase's "Chess Position Trainer" and is intended for Chessbase internal use only.


How does analyzing help me improve? This has been really frustrating for me since I don't get it. When I go through my games I spot errors and simply find better moves but then that's it. I just don't understand how this improves your game, all I did was find mistakes and correct them in a game I've already played. People keep telling me this is the best way to improve but I can't seem to get "it". If anything I suppose going through your games can show you where you might be lacking but wouldn't simply just continue learning and training in all areas of chess be a far more efficient way to improve instead of wasting time analyzing? I would appreciate examples of how analysis helped you become a better player.

First of all you have to distinguish which kind of error you made.

Opening error:

You should definitely study opening theory to avoid opening traps or get bad positions right out of the opening. On the other side when an opponent plays an unusual/bad move, you need to know how to respond and punish this move to get a better position.

Middlegame error:

Have you overseen some tactical possibilities for you as attacker/defender?

-> Try to solve tactical puzzles to get familiar with certain positions. This will also help you to spot tactics more easily the next time they occur.

Have you had the wrong plan?

-> Study positional topics like pawn formations, weak/strong points, etc. in a position and you will find the right plan straightaway.

Endgame error:

When you have no clue how to play certain theoretical endgames you will easily take a wrong step and lose drawish positions or draw winning positions.

-> Take a good endgame book to study some basics.

Also learning from mistakes you make, means you should not make the same mistake again. Thats especially true for opening errors and endgame errors in easy theoretical endgames.


Suitable defence for 1.d4 I am a 1900 (approximately) and still get depressed every time my white opponent opens with 1.d4. I just don't seem to find my way with this opening. Currently i play nimzo and QID but both are quite heavy on theory and nimzo just gets very sad if white goes for Bd2. I prefer solid positions, for instance I really enjoy play caro-kann or french against 1.e4.. So what defence against 1.d4 you think I'd enjoy? Thanks.

Try the Dutch Stonewall. If you are a French player, you can play the move order 1. d4 e6. After 2. e4 you have a French, after 2. c4 f5 you are in a dutch, avoiding the staunton gambit (not a problem in its own, but if you prefer solid play ...)

After that, with a stonewall setup you have a solid middlegame, albeit a little passive

PS: I am 1900 too.


Becoming a pretty good chess player First of all I am sorry if my English is not very good. I started to play chess some time ago. I want to start to play pretty good to have fun in tournaments but I have no idea how to create a plan of study.
Can some one explain what the difference is between an occasional player and a tournament player?
And how to make a plan to study chess?

Play. Read. Solve tactics problems, repeat. Solve endgame problems. Solve middle game problems, repeat. Analyze positions in your head. Learn famous chessgames by heart, and why specific moves was played. One of the best players in Russia had learned by heart 'all' games played by Fischer. Most average players could probably replay 50+ memorized chessgames. Find a friend to do these things together with. Or a trainer. Join a chessclub! Analyze your own games. Take help from people better than you. For tactics I like www.chesstempo.com


Why is it illegal to castle with both hands? I was watching the match between Ian Nepomniachtchi vs Hikaru Nakamura and Nakamura used both hands to castle.

Why is it illegal to castle using both hands? What's wrong with that?

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.


Is a loss of two pawns worth the negation of opponents castling? Consider a move where a bishop takes a pawn and gives check but without any defense, so the King can take the bishop.
In many openings there is a opportunity in the first moves to do so.
Can this give an advantage to the sacrificing player?

As mentioned in a comment, sacrificing a bishop for a pawn is a completely different thing than sacrificing two pawns, even when they have equal "pawn values".

Most importantly: If you sacrifice material to prevent the opponent's king from castling, your objective is to lure him out into the open and checkmate him as soon as possible (before your opponent has the chance to coordinate his now numerically superior forces). Giving two pawns for this purpose might or might not be worth it (greatly depends on the specific situation) - their absence might open additional lines for your pieces to attack the opponent's king, so their loss might actually turn out to help you. Sacrificing a bishop on the other hand counteracts your chances to deliver a quick mate: You weakened the squares around the king, but you also weakened your ability to attack these squares. Again, it all depends on the situation. If you can force a mate anyway with, say, your queen and a knight, it's all good. But then the question should be a different one.

Is it worth to sacrifice a bishop for a concrete mating attack? Hell yeah!
Is it worth to sacrifice a bishop just to prevent the opponent from castling, without a concrete mating combination? Most likely not.


How to recover from a blunder? I have been in a situation where I have not been paying attention and suddenly I move my queen to an unprotected square and it is taken.  My initial thought is:

Oh $*%! :)

But if the blunder is mediocre or not devastating, how does one get into the mindset of remaining optimistic and still playing for the win?  I have lost my queen before and still went on to win, but this is mainly due to the fact that my opponent does not know how to take advantage of the opportunity.

Many players who make a blunder, obviously depending on how big it is, might just give up in the game when they actually still have a chance to win or at least draw.

After you blunder, it's incredibly common to blunder a second time over the next few moves.  The most important thing you can do is to avoid this second blunder.

In order to do that, you should take a few deep breaths and even get up and walk around.  Although it's nice if your opponent doesn't know that you blundered (i.e. your "blunder" could be part of a deep plan so far as your opponent knows...), it's far more important to remain calm and stay focused on the game.

After this initial "cool down", now it's time to re-evaluate the game.  First, are you hopelessly lost at this point, or is the position still unclear?  Perhaps you gave away your winning advantage, but you are still equal.  If you are not lost, it is crucial that you maintain your focus and play accurately - you still have a chance to win or draw.

On the other hand, if your blunder was so egregious that your game is hopeless now, it's time to start thinking about "tricks".  For example, if you hung a pawn or two for nothing, it's time to attack with abandon.  If you can checkmate your opponent, it doesn't matter that you're losing an endgame.  If you hung an entire piece, keep all other material on the board and maintain tension in the position.  The goal here is to try to win tactically (win material back from your opponent or go for an attack).  Another common theme is to introduce time pressure into the game.  Either play tricky moves and force your opponent to get low on time, or let your own clock tick down to a minute or two and pray that your opponent blunders in your time pressure.

As a final note, when you are behind in a chess game, it's almost always good to trade pawns, but not pieces.  The rationale is that in an endgame, each pawn is a potential queen for your opponent, while on the other hand, pawnless endgames with an extra piece are notoriously difficult to convert to a win.


Why in Four Knights, Italian variation the winning percentage favours black after the move 4...Bc5? I was searching C46 Four knights, Italian variation at 365chess.com and here is what I found:

I am curious why 4...Bc5 gives black a slightly higher winning percentage. It seems to me that after 4...Bc5 it is white's turn to move and white should not have any disadvantage here.

As fuxia noted, winning percentages depend on how strong the players are, not just the opening.

Think about someone likely to play the four knights as White. Since the opening is rather unambitious and fairly easy to learn, there's a good chance this player isn't very strong. I'm not trying to generalize all players here, I'm just talking about averages. Meanwhile, Black is just following the main line moves for 1...e5. This gives no indication of Black being a weaker player.

As an aside though, the 365chess database isn't the most accurate. There are way more than 3723 games played in 4...Bc5. A look at the MEGA database or TWIC would give you more reasonable stats.


How to debug Move Generation function? I'm writing a chess engine, and I'm testing that the move generator is working correctly using a perft() function.  In perft position 2 my engine appears to be 90 moves short at ply 2.  How do authors of other engines then debug their engines?  Is there a full list of perft moves available online somewhere?

The obvious issue with using an established engine to enumerate the moves is if there's a bug in the move generation function in the established engine.

The obvious issue with using an established engine to enumerate the moves is if there's a bug in the move generation function in the established engine.

Stockfish is always perfectly correct.

Goto https://github.com/official-stockfish/Stockfish/blob/master/src/search.cpp, add a std::cout in perft(). Recompile, and then run perft. Redirect your results to a text file.

Sort the results with: sort SFMoves.txt > SortedSFMoves.txt.

Similarly, repeat for your generator, sort it and then compare with Stockfish.

Common mistakes:

En-passpant
Underpromotion
Promote with a capture

Please check the special cases in your code.


Trapped Rooks: Does Stockfish penalize more if the king can't castle temporarily? In this talkchess thread, they discuss trapped rooks and castling rights. In post #5, user @Lyudmil Tsvetkov posted:

I would give at least some 10-15cps for temporary prevention of castling.

Here is how StockFish implements it:
score -= TrappedRook * (1 + !pos.castling_rights(Us));

Here an example position.
r3kb1r/pp3ppp/4bn2/3p4/P7/4N1P1/1P2PPBP/R1B1K2R w Kq - 0 1

When searching, the move Bg2-f1 leads to the position.
r3kb1r/pp3ppp/4bn2/3p4/P7/4N1P1/1P2PP1P/R1B1KB1R b Kq - 1 1

As you can see, the White bishop has blocked castling, but pos.castling_rights(Us) for White still returns true, which means Stockfish is not penalizing for the temporary prevention of castling.
Is it intentional or is it a Stockfish bug?

White hasn't lost his castling rights. It's just not a legal move right now. There is a distinction.
White would still be able to castle king-side, if the bishop were to move.


How to play computer from a particular position on chess.com app I started playing chess a month ago and sometimes I would like to play a hard computer from a particular position (e.g., practicing not blundering in openings, or practice winning a won endgame position). However, it doesn't seem like there is a way on the Chess.com app to load a PGN and play against a particular bot. Obviously if I start a game against a 3200 bot then I won't be able to reach the part of the game I want to practice in.
Is there a way to do what I describe in Chess.com or perhaps another website/app?

You can also do this on chess.com.

Go to the "Learn" Tab
Click on "Analysis"
Setup your position via FEN or just by placing pieces
Click "Finish vs Computer"


How to counter white's attempt to get a massive center in the Giucco Piano? [FEN ""]

1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3

When white plays 4. c3 and prepares to push d4 to get a massive center, how is it possible to prevent them from doing so, or at least put a lot of pressure on the center with it? I don't have trouble dealing with this in longer time controls because I can find ways attack the center, but how do I deal with this in blitz? When with the black's side I feel like playing against the Evan's gambit without being up a pawn.

c3 by white is called the Moller Attack. The reason you do not see it at high levels is that the sting has been taken out of it over the years. Basically, it comes down to breaking up the center with Nxe4, or hitting back in the center with d5, before white can finish developing and fortify the center.

There are a few lines you need to know.

 [FEN ""]

 1. e4 e5 2. Nf3 Nc6 3. Bc4 Bc5 4. c3 Nf6 5. d4 exd4 6. cxd4 (6. e5 d5 7. exf6 dxc4 8. fxg7 Rg8 9. O-O Qf6 10. Re1+ Be6 11. Bg5 Qxg7 12. g3 h6 13. Bh4 Qg4 {and black is quite safe, and much better}) Bb4+ 7. Nc3 (7. Bd2 Bxd2+ 8. Nbxd2 d5 9. exd5 Nxd5 10. Qb3 Nce7 11. O-O O-O 12. Rfe1 c6) 7... d5 (7... Nxe4 8. O-O Bxc3 9. d5 Bf6 10. Re1 Ne7 11. Rxe4 d6 12. Bg5 Bxg5 13. Nxg5 h6 14. Qe2 hxg5 15. Re1 Be6 16. dxe6 f6 17. Re3 c6 18. Rh3 Rxh3 19. gxh3 g6 20. Qf3 Qa5 21. Rd1 Qe5) 8. exd5 Nxd5 9. O-O Be6

And you play a standard isolated queen-pawn position.

The main line I gave with 7...d5 is probably not as good at taking on e4, but that line is much more dangerous and has a number of side roads that white can try.


Are alphanumeric style chessboards becoming less popular? It seems that most of the chessboards being offered for sale in the House of Staunton or Regency Chess - except for cheap vinyl tournament chess boards - do not have alphanumeric coordinates marked on the four sides.

Has this style fallen out of favor or are the markings considered to interfere with a minimalist look or even distract during play? I have possibly over 500 games under my belt but still being able to rely on markings is handy especially when taking notes or studying.

They are still selling boards with coordinates and still using them in official competitions.

With experience you will see that you will no longer need numbers and letters to help you throughout the game (just think battleship).


Looking for books specializing in chess play from black I play online chess at a popular site and while playing from black, I win 58% of my games. I think I have a natural tendency to be a 'counterpuncher'. I seem to derive a perverse enjoyment in playing as the underdog and find it ammusing on some level to be able to survive my opponent's best attack. I'm a 1720 rated player in the 84th percentile of 30k players using E.L.O rating system. I'd like to advance my knowledge from black but can't find much devoted material. I'm guessing my otb play would be 1500-1600.

It was my pleasure and recognition to see somebody asking to recommend some books how to play with BLACK. They were suggesting 3 books. All of them happened to be mine:

Black is OK! (1988),
Black is still OK!
Black is OK forever!

It shows the good taste of the members... Gratefully I draw your attention to some more. Winning with the Gruenfeld (Batsford, 1986) which could not be a BLACK is OK! book by name, for this "Winning with ..." was a Batsford series. But I assure it qualifies by the content. Finally there is a Sicilian subvariations (1994) which appeared in 5 languages simultaneously. And last there is a 'Rare Openings' book (English, Deutsch, French) which deals with everything but 1.d4, 1.e4, 1.c4 and 1.Nf3. I'm glad to join you and look forward to receive your comments, thoughts, etc.

I'm waiting for your messages too in: aa_ok@interware.hu ADORJÁN András


Illegal Move Missed-Too Late? This question is about standard games under USCF rules (if FIDE is different, I'd like to know).  Say that one side makes an illegal move-specifically, castling through check.  Neither player notices.  Five moves later, the same side that made the illegal castle makes a now legal move to create checkmate.  During analysis, the losing side recognizes that the castling was illegal.  I believe that once the checkmate position is reached, it is too late to correct the illegal move, even though it is within the last ten moves. Is that correct?  Would the answer be different if the checkmate was created using the rook that was used in the illegal castling?

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 4.7 apply to the
  move replacing the illegal move. The game shall then continue from
  this reinstated position.

So you can't claim an illegal move after the end of the game.

On the other hand, you can't checkmate using an illegal move:

  5.1  The game is won by the player who has checkmated his opponent’s king. This immediately ends the game, provided that the move producing
  the checkmate position was in accordance with Article 3 and Articles
  4.2 – 4.7.

I don't know about USCF rules, but I suppose they are similar.


Does the design of chess pieces affect professional chess players at all? There are some unique designs of chess pieces such as the following:

(For the one above, I am not even sure if the setting up of pieces is correct.)

I will not feel comfortable playing with any of these weird chess sets and if I have to play, my understanding of the positions will definitely be negatively affected.
Am wondering if this will affect professional players or other strong club players at all. Do designs of chess pieces affect them at all?

Am wondering if this will affect professional players or other strong
club players at all. Do designs of chess pieces affect them at all?

The short answer is "No" for the simple reason that they will never play any tournament chess with anything other than the standard Staunton design. The reason for that is given in the FIDE document Standards of Chess Equipment, venue for FIDE Tournaments, rate of play and tie-break regulations
According to the introduction -

This document defines the general standards for chess equipment and
conditions of play, rate of play and tie-break regulations to be used
in FIDE competitions.

On the subject of chess equipment it says this:

1. Chess Equipment
1.1 The chess equipment offered by the organisers (hosts) of a FIDE or Continental Championship, Olympiad and other FIDE registered
tournaments shall conform with the standards mentioned below, and
shall be approved by the Chief Organiser and the Chief Arbiter.
1.1.1. It is recommended, that the chess pieces, boards and clocks, used in the World or Continental top level competitions be
approved by participating players. Their approval shall be obtained
for other equipment the table, chairs etc. In case either side
disagrees, the equipment to be used shall be decided by the Chief
Organiser or the Chief Arbiter of the event, bearing in mind the
standards for its size and form as mentioned below.
1.1.2. It is highly recommended that the chess equipment used in a competition is the same for all participants and all games.

On the design of the pieces it says:

2.3 Form, style of pieces
Recommended for use in FIDE competitions are pieces of Staunton style.
The pieces should be shaped so as to be clearly distinguishable from
one another. In particular the top of the King should distinctly
differ from that of the Queen. The top of the Bishop may bear a notch
or be of a special colour clearly distinguishing it from that of the
Pawn.

Note that in the US lower level tournaments often require players to bring their own equipment. The USCF has its own regulations regarding equipment detailed in Chapter 4 of their US Chess Rulebook. Chapters 1, 2 and 11 are available free online but the USCF sees fit to charge for the rest of their rulebook. I would be slightly surprised if this allows non-standard designs.


Which book should one read if they want to play like Tigran Petrosian? According to Wikipedia, the former world champion Tigran Vartanovich Petrosian has "almost impenetrable defensive playing style, which emphasized safety above all else".

Here defensive is by no means passive and emphasizing safety above all else is surely not a bad thing (see Petrosian's accomplishments). Which book would you recommend, if one wishes to play like Petrosian?

One of Petrosian's greatest strengths was his prophylactic thinking; i.e., identifying threats before they arise and neutralizing them. A book which discusses this concept would be good. For example, "Recognizing Your Opponent's Resources: Developing Preventive Thinking".

If you want to learn more about Petrosian himself, part 3 of Kasparov's My Great Predecessors series would be good. In this book he goes over the games of Spassky and Petrosian.


Can two Kings stand next to each other? My white King is separated from the Black King by one square (between) which is protected by my white rook.  I moved my white King next to the black King putting him in check (from the square protected by my rook).  My opponent says that this is an illegal move because two Kings cannot face each other.  I contend that my white King can threaten the black King from a protected square (by my rook). Who's right?

Your friend is right. Think of it in terms of capturing the king: check means that your king could be captured on your opponent's next move. If you could move your king next to your opponent's king, your king could be captured on your opponent's next move; the fact that after that you could capture your opponent's king doesn't change that: your king has been captured, and you've lost the game.


What does the annotation symbol "TR" mean? I've seen commentators use this symbol at the end of their analysis but I don't know what it means.  Does anyone know?

Descriptive Notation. It is an alternative notation for recording chess games.

From Wikipedia:

  Descriptive notation is a notation for recording chess games, and at
  one time was the most popular notation in English- and
  Spanish-speaking countries (Brace 1977:79–80) (Sunnucks 1970:325). It
  was used in Europe until it was superseded by algebraic notation,
  introduced by Philipp Stamma in 1737.

The abbreviation TR seems to refer to the spanish descriptive notation:

  The initials are taken from the equivalent Spanish words: dama for
  queen, rey for king, torre for tower (i.e. rook), caballo for horse
  (i.e. knight), alfil for bishop and peón for pawn. The files are named
  after the initials of the pieces on the back rank, with those on the
  queen's side being suffixed by the letter "D" and those on the king's
  side suffixed by the letter "R". From left to right along the back
  rank, this gives: TD, CD, AD, D, R, AR, CR, TR.


How to play the French as White Club opponents frequently play the French Defence again me, and I have trouble countering it with the Advance variation, since  Black gets active pieces. Is there another good variation that avoids the Winawer, while giving White less problems?

Three most common replies to the French are 3.Nc3, 3.Nd2 and 3.e5, in your question you are ruling out 3.Nc3 and 3.e5, so 3.Nd2, the Tarrasch, seems like a natural suggestion, and it is less sharp than Winawer and if closing of the center happens it is on better terms for white than in Advance variation, so it might be worth a look. But if you want to avoid French structures in general, then by all means play the exchange variation that Brian Towers has suggested.


Black's 6 move in open Sicilian Is moving the Knight to c6 considered a stronger move than the Najdorf pawn to a6?

You probably mean Najdorf vs Classical variation in Sicilian defense:

[FEN ""]
1. e4 c5 2. Nf3 d6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 a6 (5... Nc6)

Since they're both normal opening lines, you can't say which one is better. This is mostly matter of taste.

On the other hand on the highest level Najdorf is more played (I can't even remember a top game in the Classical variation). That means Najdorf is more trendy now.

It's true that Classical variation is not so attractive any more, because it is deeply analyzed. Najdorf has still a lot to offer...


Can playing against Computer help? I am a begineer level player on chess.com with rating around 1500. I play daily 2-3 games with 15|10 mins time control for each player. I find it difficult to get time to study chess books, and was thinking of playing against a Chess Engine. I have Shredder Chess installed in my system.

How can I make use of it to help improve my games. I set it at the highest strength and play though I have the option to take back and replay my moves. How to make the best use of the Chess engines?

For computer engines it is much harder to simulate a "human" style than just playing good. If you want to improve your play against humans, play against humans. Use the engines to analyze your games. As already commented, fast or blitz games (but please not faster that ~5 min, as the "quality" of the games decreases rapidly at this point) are a good way to learn to "see" quickly dangers and opportunities, and to have more tactics as usual on the board (as positional play becomes only important after you don't lose most games tactically).

I recommend lichess.org, which is free and offers (at least) three nice features: Computer assisted error checking after games, training positions from real games, and invitation by eMail


Does anyone have the 1996 correspondence game between De Groot-Simmelink? As far as I know, here are the first 12.5 moves are as below. Does anyone have the rest of the game?

[FEN ""]

1. d4 Nf6 2. c4 Nc6 3. Nc3 e5 4. d5 Ne7 5. h4 Neg8 6. a3 a6 7. Nf3 Ng4 8.
Ng5 f5 9. Qc2 Bc5 10. e3 Ne7 11. Be2 Nf6 12. b4 Ba7 13. Bb2

This question seems to have been answered by TD in ChessPub Forum. I post the answer below:

[fen ""]
[Date "1996"]
[Round "?"]
[White "De Groot, Adrianus Dingeman"]
[Black "Simmelink, Joop Theo"]
[Source "ChessBase"]

1. d4 Nf6 2. c4 Nc6 3. Nc3 e5 4. d5 Ne7 5. h4 Neg8 6. a3 a6 7. Nf3 Ng4 8. Ng5 f5 9. Qc2 Bc5 10. e3 Ne7 11. Be2 Nf6 12. b4 Ba7 13. Bb2 h6 14. Nf3 d6 15. c5 e4 16. cxd6 Qxd6 17. Nd2 O-O 18. Rd1 b5 19. Bxb5 axb5 20. Nxb5 Qd7 21. Nxc7 Rb8 22. d6 Nc6 23. Nc4 f4 24. Bxf6 fxe3 25. fxe3 Qg4 26. Nd5 Be6 27. Ne7+ Nxe7 28. dxe7 Qg3+ 29. Qf2 Qxf2+ 30. Kxf2 Rxf6+ 31. Ke1 Kf7 32. Ne5+ Ke8 33. Nc6 Bd7 34. Nxb8 Bxb8 35. Rd4 Ra6 36. Rf1 Bg3+ 37. Kd2 Bc6 38. Rc1 Bb7 39. Rc5 Kxe7 40. Ra5 Rxa5 41. bxa5 Bc7 42. a6 Bxa6 43. Rxe4+ Kf6 44. Rd4 1/2-1/2


Is there a web version of a chess clock for mobile phones without (distracting) advertisements? I am looking for a very simple Chess Clock (simple design - see picture) to use from the phone browser WITHOUT having to download an app. I already know apps who have this I am looking for a web version!
This is an example for a good app:

And here is an example of a bad web version with bad design and too many distractions, looks especially bad on mobile:

Best Solution:

chessclock.org - add the website to the home screen on your phone and tilt the phone to the side

Added in the comments: chessclock.iphonemarks.com

Original suggestions:

skakur.dk
ksloan.net/chessclock


Is this a legitimate defence to Ruy Lopez openings? When I play the Ruy Lopez opening, I usually get my bishop chased all the way down to the second rank by two pawns. I don't know if this is common at higher levels of play but it seems like a pointless pursuit.

[FEN ""]

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 b5 { Spanish Game, Morphy Defence, Caro Variation } 5. Bb3 a5 6. a3 a4 7. Ba2 *

Does doing this give either player an advantage at any point during the game?

It is extremely uncommon for Black to play like this at the higher levels, and that is because, as you stated, it's pointless. Black achieves nothing in particular by this chase, and White ends up with a standard opening advantage. Worth noting, however, is that after 5...a5 by Black, White is in no way forced to play a3. A standard developing move will do, as the bishop can go to d5 if nothing else.


Variant in which two pieces can occupy a single square A friend and I tried playing this variant yesterday.  My question is:

  Surely someone has looked at this before.  Does it have a standard name?  Or is there something obviously wrong with it that my friend and I missed?

Sometimes this kind of drastic change to the rules produces a game that is obviously no good.  (Consider the variant in which the board is turned into a torus; White has already lost, or perhaps wins immediately  with 1. QxK, depending on how you look at it.)  This variant didn't seem to have an obvious failure, and we had a good time playing one game and seeing how the tactics differed.

Specifically, the variant we played was:

All pieces move and capture the same as in standard chess, except:
Up to two pieces may occupy the same square.
A piece may move into an occupied square, but not through it.
A piece moving into a square occupied by two pieces of the opposite color may capture either, but not both.
Pieces of opposite colors sharing a square do not threaten one another.

So for example, it was legal for White to open with 1. Rh2, and have the rook and pawn sharing h2.  Having done this they could then continue on the following move with 2. Rh4.  But 1. Rh4 was
illegal.

Since every chess variant imaginable has been tried out, I expect this one has also.  I'd like to read about it, but I don't know what to search for.

Pierre-Françoys Brousseau found a similar variant on Guy T Shafer's blog “Insane Chess”.   It says:

  Crowded chess

  Requires standard chess set & board. Pieces setup, and capture as normal.

  Pieces move as normal, except any 2 non-pawn pieces of the same
  color may share the same square. Men cannot pass through an
  occupied square: pieces are blocked by men as usual. But you may
  pass your own piece in 2 turns (one to move onto the occupied
  square, another to move off that square). Pawns may never share a
  space with any piece.

This is a little different from our variation, in which pieces of opposite colors may share space, and pawns may share space.

Unfortunately there is no real discussion there.