title: Is this an incorrect draw by chess.com?

text:
# Question
Title: Is this an incorrect draw by chess.com?
> Is this an incorrect draw by chess.com?

I just played a game on chess.com with the final position as below (I am black):

```
[FEN "8/8/2b5/7P/8/2k1N3/5PP1/6K1 w - - 0 59"]

```

My opponent's time ran out and the game was called a draw due to timeout vs. insufficient material. I believe this is incorrect as I can mate my opponent in the following way:

```
[FEN "8/8/2b5/7P/8/2k1N3/5PP1/6K1 w - - 0 59"]

1. Kh1 Kd2 2. Nf1+ Ke1 3. Nh2 Kxf2 4. h6 Bxg2#

```

# Answer
> 33 votes
From chess.com support, the site follows the USCF rules on draw vs insufficient material in that if there is insufficient material\* for a *forced* mate and the opponent does not have a forced win, it is a draw.

See also USCF vs FIDE by Greater Peoria Chess Foundation:

> Insufficient Material
>
> FIDE. It is possible to lose on time in situations that are a draw under US Chess rules. For instance, GM Friedel (IM Friedel at the time) lost on time with a king and rook vs. king and knight. Under the FIDE laws of chess, the game is drawn when one player runs out of time only if there is no legal sequence of moves by which the opponent could checkmate the player. Since there is a helpmate that allows a king and one knight to checkmate a player with a king and rook, GM Friedel lost the game. (Note: Earlier versions of this page incorrectly attributed this loss to GM Nakamura. The game in question is IM J. Friedel - GM S. Halkias, Bad Wiessee Open, Germany, 2007. See this story on Chess Life Online for more details.)
>
> USCF. US Chess rule 14E (insuffient material to win on time) specifies cases where the game is drawn even if one player runs out of time. One of the cases listed in rule 14E is the opponent having only a king and knight (and not having a forced win).

\*Insufficient material is defined by the USCF as if the opponent has:

* **Lone king**
* Only **king and bishop** or **king and knight**, and does not have a forced win
* Only **king and two knights**, player has no pawns, and opponent does not have a forced win

# Answer
> 10 votes
Yes, you are correct. That is a known defect with chess.com. It would have been enough for your opponent to just have a pawn for you to still be able to checkmate them. The pawn could promote to a knight and your king and bishop could then deliver checkmate with this position.

```
[FEN "8/8/8/8/8/6k1/6b1/6NK w - - 0 59"]

```

# Answer
> 6 votes
It's a great question. A very similar situation very famously occurred between Alireza Firouzja and Magnus Carlsen in 2019. The quick version:

* After a very intense game, Magnus was down to a king and bishop when Firouzja's clock ran out. Firouzja thought this was a draw because bishop and king is typically insufficient to checkmate an opponent unless the opponent plays very specific moves that allow the checkmate. **But** because Firouzja still had a bishop on the board, it meant it was *theoretically* possible for Carlsen to mate him!
* It is explained excellently here.

Here is the final position (Magnus with the black pieces):

```
[Title "Alireza Firouzja-Magnus Carlsen, World Blitz Championship, Moscow Russia, 12/30/2019"]
[FEN ""]
[startply "132"]

1. e4 e5 2. Nf3 Nc6 3. Bb5 a6 4. Ba4 d6 5. O-O Bd7 6. c3 g6 7. d4 Bg7 8. h3 Nf6 9. Bc2 O-O 10. Re1 Re8 11. Nbd2 Qe7 12. Nf1 Qf8 13. Ng3 Bh6 14. Ng5 Nd8 15. Bb3 Ne6 16. h4 Rad8 17. Be3 Bg7 18. h5 Bh6 19. Qc1 Ng4 20. Nxe6 fxe6 21. Rf1 Nxe3 22. fxe3 Qe7 23. hxg6 hxg6 24. Qd2 exd4 25. cxd4 Kg7 26. Rf3 Rf8 27. Raf1 Rxf3 28. Rxf3 Rf8 29. Qc3 c6 30. Nf1 e5 31. Rxf8 Kxf8 32. Qc4 Qf6 33. dxe5 dxe5 34. Qb4+ c5 35. Qxb7 Bb5 36. Qc8+ Ke7 37. Qxc5+ Qd6 38. Qxd6+ Kxd6 39. Bf7 Bxf1 40. Kxf1 g5 41. Ke2 Bf8 42. Kf3 Ke7 43. Bc4 a5 44. Ke2 Kd6 45. Bd5 Be7 46. Kf3 Bd8 47. Kg4 Be7 48. Kf5 Bd8 49. g4 Be7 50. a3 Bd8 51. b4 axb4 52. axb4 Be7 53. b5 Bd8 54. Kg6 Kc5 55. Kf5 Kxb5 56. Kxe5 Kc5 57. Ke6 Ba5 58. e5 Bd2 59. e4 Bc3 60. Kf5 Kb6 61. e6 Kc7 62. Kg6 Kd8 63. Kxg5 Ke7 64. Kh5 Bd2 65. g5 Bf4 66. Kg4 Bd2

```
* Yet, on chess.com, the exact same game would be a draw!

---
Tags: rules, online-chess, draw
---


title: A specific draw etiquette

text:
# Question
Title: A specific draw etiquette
In one of my last games, I offered a draw. Now for what the rules don't say...

He had quite to chew on the offer. Half an hour he was sitting and pondered whether he could risk to play to win. I, on the other cheek, always have ants in my pants. Technically, there would be nothing wrong with just walking away - it's not my move, the draw offer is marked on both our sheets, he could stop the clock and either wait for me to come back or hand in the result. But I found walking a bit impolite.

Thus: "Sitting on the dock of the bay" or "Runaround Sue"?

# Answer
> 12 votes
If the opponent ponders for several minutes over your draw offer and neither of you is in zeitnot, I see no offense at all in having a walk while waiting for his answer. I have done that several times, and so have my opponents, without anyone feeling embarassed.

Usually if I accept the draw offer I just stop the clock and wait for the opponent's come back to shake hands, or if I refuse I just play my next move and mutter "I'll continue" (or nothing at all) when they sit back...

# Answer
> 8 votes
There is nothing, either in the rules of the game or in "etiquette", which requires either one of you to remain at the board. Your opponent is required to remain in the playing area and you are required to remain in the playing venue. That is all.

Some years ago in a league match, in a dull endgame with little for either me or my opponent, I offered a draw. Before doing so I checked the other boards. Winning one, better on one and even on the other. My opponent and I both had about 30 minutes on the clock.

Not surprisingly my opponent got up and had a look at the other boards. However he didn't come back and make a decision. Instead he stood and watched the other games for about 20 minutes by which time the win for us had turned into a draw and the other two games had turned in to losses. He came back to the board with ten minutes remaining and accepted my draw offer.

---
Tags: draw, etiquette
---


# Question
Title: Why does using an engine in your chess games help?
When I play against a max level chess engine, I can't win. However, when I calculate all the moves with a chess engine, I win every time. If chess computers are all around the same level, how was I able to checkmate the Komodo Engine with Stockfish 15? The game is here.

# Answer
> 2 votes
> If chess computers are all around the same level

They aren't.

> how was I able to checkmate the Komodo Engine with Stockfish 15?

Using an engine is a bit like playing with "take-backs". You are never going to blunder. Somebody who knows nothing about chess but can follow an engine and copy one engine's best move to another game with another engine is still going to "play" better than Magnus Carlsen. That reflects nothing about them and everything about the choice of engines.

---
Tags: engines
---


# Question
Title: Has a position being a draw under FIDE 5.2.b before a forced recapture ever come up in a tournament?
Tom7 points out that FIDE article 5.2.b reads:

> The game is drawn when a position has arisen in which neither player can checkmate the opponent’s king with any series of legal moves. The game is said to end in a ‘dead position’. This immediately ends the game, provided that the move producing the position was legal.

As Tom7 explains, examine the following position. After white plays Qxd7+ it is *immediately* the case that no legal sequence of moves can lead to a checkmate. This is true *before* black recaptures the queen — and therefore, black *cannot* recapture the queen, as the game is already a 'dead position' by FIDE rule 5.2.b, and the game is already over. Specifically, there is no legal continuation of the game in which either player is mated (helpmated or otherwise), and therefore the game is already over after Qxd7+ (1/2-1/2).

```
[FEN "3k4/3q4/8/5Q2/8/2K5/8/8 w - - 0 1"]

1. Qxd7+

```

This seems to be the pretty clear conclusion of 5.2.b, and I don't see how to escape this. Sure, in practice, players would probably "play" Kxd7 as a convention, even though the game is already over before the invalid recapture.

But what if this situation arose in tournament?

1. White plays Qxd7+.
2. White hits the clock — I don't believe this is even necessary, as rule 6.2.a explicitly cites 5.2.b as "completing" a move immediately, due to the game immediately being over, much as it isn't necessary to hit the clock after delivering checkmate.
3. Black's flag falls.

The lay misinterpretation of 5.2.b would be that black's flag fell while white still had a queen, and therefore black loses. But a close reading of 5.2.b and 6.2.a shows that the game was already over the moment the queen was placed next to the king, and black had no obligation to do anything further — just sign the score sheets and get lunch.

Has this ever come up in a tournament? I realize this is rules-lawyering, but e.g. Firouzja lost to Carlsen due to a possible helpmate, so I assume FIDE has at least some appetite for taking their own rules seriously.

Note: Closely related questions have been asked on SE, e.g. here, linking to resources like: http://wismuth.com/chess/illegal-moves.html. My question differs in that I'm asking about an incredibly common position. This sort of endgame occurs all the time, and is technically already dead, while these other questions are asking about "obscure" dead positions with bizarre locked up pawns and bishops and the like — I'm specifically asking about this incredibly common case of forced recaptures like the above, that I think most folks don't realize are already dead.

# Answer
> 2 votes
Software which can answer this question now exists, but has not yet been applied to FIDE-rated tournaments.

Miguel Ambrona (see https://chasolver.org/FUN22-full.pdf, presented at a conference in Sicily, Aug-2022) an algorithm to determine position deadness, and has applied it to the corpus of all Lichess games:

```
The Lichess Database of standard rated games includes 3,367,175,192 games to date (May
2022). We have applied our algorithm from Figure 9 to the final position of all games
that ended in a timeout and that were classified as 1-0 or 0-1. In total, 1,067,375,745
games (about 32% of all games) were analyzed in about 107 hours of CPU time (359 µs per
position  on average). All experiments were performed on a 3.5GHz Intel-Core
i9-9900X CPU with 32GB of RAM, running Ubuntu 20.04 LTS.

Our analysis led to identifying a total of 90,546 games that were unfairly classified.
Namely, games that were lost by the player who ran out of time, but their opponent could
not have checkmated them by any possible sequence of legal moves. We refer to Appendix B
for some remarkable positions of unfairly classified games; the remaining can be found
on the following link (where our tool can also be tried interactively without
installation): https://chasolver.org.

Our analysis identified all the unfairly classified games in the database. In all other
games, the tool provided a checkmate sequence for the player who did not run out of time.

```

Here is one naturally-occurring dead position that lichess mis-classified:

```

[FEN "8/8/p7/PP6/K7/1R6/1R6/k7 w - - 0 1"]

```
1. ... axb5+ 2. Ka3 (2.Kb4,Kxb5,Rxb5 stalemate) b4+ 3. Ka4,Kxb4,Rxb4 stalemate

Miguel states:

```
We believe that our algorithms are suitable for practical use and in particular chess
servers (and chess software) can leverage them to accurately classify games after a
timeout, following Article 6.9 of the FIDE Laws of Chess. Furthermore, given the
results of Figure 11, chess servers could also apply our tools after every single
move during games, to terminate games as soon as a dead position is achieved,
correctly applying Article 5.2.2.

```

It is evidently now computationally feasible for a similar exercise to be conducted for databases of FIDE-rated tournament games. One might identify positions which, like the example quoted above, would end just prior to a mandatory capture.

Miguel separates "dead position" into 2 non-mutually-exclusive cases: "White can't mate" & "Black can't mate". Each is solved separately under his algorithm, and is useful in isolation because of Law 6.9 concerning time-out.

His tool successfully solved all positions from the Lichess Database, (either finding a mate, or proving that none could exist). He notes that some artificial positions involving multiple floating bishops might take longer to terminate. Since the algorithm also works for every composition that I tried out with him, including some quite complicated ones, this is probably not a significant limitation.

This is not entirely unexpected since we know from other work that determining deadness is PSPACE-complete when considered over nxn board, see: https://arxiv.org/abs/2010.09271.

See also the se question linked to in the question, When checkmate is impossible in a position, where Miguel does mention his own work.

---
Tags: rules, fide, dead-position
---


# Question
Title: What is "mating potential" in the FIDE Arbiter's Manual meant to mean?
While researching an answer for another SE.chess question (Has a position being a draw under FIDE 5.2.b before a forced recapture ever come up in a tournament?), I stumbled across the following issue.

The FIDE Arbiter’s Manual annotates the Laws of Chess. The 2022 edition (and also the 2021 edition - I haven't checked further back) contains an enigmatic comment regarding dead position:

```
"1.5 If the position is such that neither player can possibly checkmate the opponent’s
king, the game is drawn (see Article 5.2.2)."

If neither player can win then the game is automatically decided as a draw. The arbiter
should therefore step in to declare this when:

(a) neither player has mating potential, or
(b) the position is such that neither player can get checkmate (known as a ‘dead
position’).

The simplest example of (a) is K v K.

The following, where white has just played h5, is an example of a dead position:

```

```
[Title "Dead Position"]
[FEN "8/2b1k3/7p/p1p1p1pP/PpP1P1P1/1P1BK3/8/8 w - - 0 1"]

```

Article 5.2.2, which has no annotations in the manual, states:

> "5.2.2 The game is drawn when a position has arisen in which neither player can checkmate the opponent’s king with any series of legal moves. The game is said to end in a ‘dead position’. This immediately ends the game, provided that the move producing the position was in accordance with Article 3 and Articles 4.2 – 4.7."

(Articles 3 & 4 cover movement rules and touch-move respectively.)

So what is the undefined and otherwise unreferenced term "mating potential" meant to mean?

# Answer
> 1 votes
As far as I can see, categories (a) & (b) are the same. Reading 1.5 & 5.2.2, which are not complicated, the given example KvK obviously *is* a dead position.

Maybe the intention is to distinguish between positions which have "insufficient material" for checkmate, in the old phrase, and those which are blocked positions. But this is very unclear.

In any case there are other kinds of dead positions, namely those which are inexorably headed along a sequence of moves (e.g. forced capture) which lead to (1) insufficient material (2) stalemate or (3) blocked position. These three fates are not mutually exclusive. There are known positions whose fate may branch but still inexorably leads to either (1) or (2). Similarly positions doomed to reach (2) or (3). Stalemate itself is *not* a dead position, as it is covered by separate laws, and I suppose the game is evaluated to be mate/stalemate *before* any examination of deadness.

I suggest to arbiters the following annotation to replace the current one:

```
"1.5 If the position is such that neither player can possibly
checkmate the opponent’s king, the game is drawn (see Article 5.2.2)."

If neither player can win then the game is automatically decided as a draw by dead
position. The arbiter should therefore step in to declare this.

Examples include:

(a) KvK, KBvK, KNvK,

(b) The following, where White has just played h5:

```

```

[FEN "8/2b1k3/7p/p1p1p1pP/PpP1P1P1/1P1BK3/8/8 w - - 0 1"]

```

```
(c) The following, where White has just played Qxd7:

```

```

[FEN "3k4/3Q4/8/8/8/2K5/8/8 w - - 0 1"]

```

# Answer
> 1 votes
It is perhaps worth starting by pointing out that the FIDE Arbiters Commission and the FIDE Rules Commission are two separate entities. This FIDE article defines what the roles and responsibilities of the different commissions are.

Here is what it says for the Arbiters Commission (ARB):

> ARB has the following ongoing responsibilities:
>
> * Licensing of arbiters (National, FIDE and International level)
> * Evaluating title applications and classification of arbiters in categories to be presented to the FIDE Council or the General Assembly
> * Supervising of FIDE seminars and workshops for arbiters (endorsement, advertisement, archiving)
> * Administration of the FIDE arbiter’s database
> * Initiating and leading new projects to support arbiter development
> * Organising seminars, workshops and joint training courses with other Commissions
> * Designing the curriculum for arbiter seminars and examinations
> * Providing reference documents for trainees and lecturers
> * Producing official publications (Arbiters Manual and Arbiters Magazine), which may be printed and distributed
> * Advertising seminars and development projects and initiatives on their official website and social networks
> * Enforcing the Disciplinary Regulations for Arbiters
> * Selecting Arbiter Panels as required by the Arbiter Appointment Regulations

Here is what it says for the Rules Commission (RC):

> RC defines and updates the Laws of Chess and Online Chess Regulations, in consultation with players, event organisers and other Commissions, to provide a standard set of rules for chess to be played worldwide. ... RC is responsible for suggesting amendments for the following regulations to Council, and applying them in their ongoing responsibilities:
>
> * Laws of Chess
> * Online Chess Regulations
> * General Regulations for Competitions

So, when the ARB publishes its annotated copy of the FIDE Laws of Chess its annotations are simply clarifications, advice and suggestions. Only the Rules Commission can actually specify what the rules are. They should not be quoted as if they have the same force as the actual Laws themselves (as has been pointed out to me when I have done so in front of senior international arbiters).

> So what is the undefined and otherwise unreferenced term "mating potential" meant to mean?

Very simply, if white has "mating potential" then white has the "potential" to deliver mate. The Merriam-Webster dictionary defines "potential" as:

> existing in possibility : capable of development into actuality

Clearly in the kind of blocked position you give in your question there is no "existing possibility" of mate. In other words there is no mating potential. Similarly in K v K or KN v K or KB v K endgames. Similarly in KQ v K when the queen is unprotected next to the opponent's king and the only legal move is KxQ.

All the annotation is doing is restating 5.1 in a different form. Whether it is a clearer form is another matter.

---
Tags: rules, fide, draw, dead-position, arbiters
---


title: Caro-Kann Apocalypse Attack

text:
# Question
Title: Caro-Kann Apocalypse Attack
What are the main points, tactical or otherwise, backing up the so-called Apocalypse Attack vs the Caro-Kann?

```
[Title "Caro-Kann Apocalypse Attack"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1. e4 c6 2. Nf3 d5 3. exd5 cxd5 4. Ne5!?

```

Is it an opening based on a few cheap tricks? And if so, what are these tricks?

There is a long article here

http://www.kenilworthchessclub.org/articles/opening/apocalypse/apocalypse.htm

but it is difficult to me to sum up the main ideas or tactical themes in a more concise way.

# Answer
> 3 votes
Maybe it's about having a Knight on `e5`, which cannot be dislodged easily with pawn moves. I think it's not so significant though, because black can still at least exchange it against the knight on `b8`, which could come to `d7` or `c6`. `d7` might prevent the exchange o black's bishop against the knight on `e5`. If white manages to get black to exchange on `e5`, white will have a pawn on `e5` most likely. Maybe a point is to still have a pawn there, although white didn't move `e4-e5` earlier? I don't really see how `Ne5` is really that helpful to be honest. It doesn't even look that interesting to me or much different than other positions.

# Answer
> 1 votes
Aside of 4...Nc6, black can also play 4...a6 (which prevents Bb5) and 5...Nc6. Black will then place the pieces like in the position after 13...Ne7, pressing against d4. Black can also consider g6 and Bg7 instead of Be7-f6.

```
[Title "Analysis"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1.e4 c6 2.Nf3 d5 3.exd5 cxd5 4.Ne5 a6
    ( 4...Nc6 $5 )
5.d4 Nc6 6.Nxc6
    ( 6.c3 $5 Bf5 $10 )
6...bxc6 7.Nd2
    ( 7.Bd3 Nf6 8.h3
        ( 8.O-O Bg4 $10 )
    8...Qb6 9.c3
        ( 9.Be3 $5 )
    9...e6 $10 )
    ( 7.c4 g6 $10
        ( 7...Bf5 $5 )
    )
7...Bf5 8.c4
    ( 8.c3 $6 e6 9.Nf3 Bd6 10.Bd3 Ne7 $15 )
8...e6 9.c5 Be7 10.Be2
    ( 10.Qa4 Qc7 11.Nf3 Bd8 $10 )
    ( 10.Nf3 Bf6 11.Bd3 Be4 $10 )
10...Bf6
    ( 10...Nf6 $5 )
11.g4
    ( 11.Nf3 $6 Ne7 12.O-O Bg4 $15 )
11...Bg6 12.Nf3
    ( 12.h4 $2 h5 $17 )
12...h6
    ( 12...h5 $2 13.g5 Be7 14.Qa4 $18 )
13.Qa4 Ne7 14.h4 Be4
    ( 14...O-O $2 15.g5 $18 )
15.Bf4 O-O $1 16.h5
    ( 16.g5 $2 Ng6 $17 )
16...Bg5 17.Bxg5
    ( 17.Bd6 Bxf3 18.Bxf3 f5 $10 )
17...hxg5 18.O-O-O Qc7 19.Qa3 Qf4+ 20.Qe3 Qxe3+ 21.fxe3 f6 22.Rh2 a5 23.
Nd2 Kh7 24.Nxe4 dxe4 25.Bc4 Nd5 26.Bxd5 exd5 27.Rf1 Kh6 28.Rhf2 a4 29.Kc2
Rfb8 30.Kc3 $10

```

Black has some initiative in the later part. The white pawn moves (c4-c5, g4, h4, h5) restrict him, but also create a vacuum (allowing Qc7-f4+ for example). But if white does not play c4-c5 then Bd6 and Ne7 is a harmonic setup.

# Answer
> 0 votes
The Apocalypse attack is an anti-Caro-Kann weapon. The main point of the Caro-Kann is to achieve a better French defense, possibly at the cost of some tempo. By better French defense, I mean a solid defense where Black holds a pawn on d5 but hasn't trapped their light square Bishop and will typically develop it to f5 or g4 before pushing e6. By loss of tempo, I mean that in a lot of lines when White does not initiate the pawn trade on d5, Black will play pawn c6 to c5 to trade it for a central pawn. For example :

```
[Title "Caro-Kann Defense: Advance Variation, Botvinnik-Carls Defense AKA the better French"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1. e4 c6 2. d4 d5 3. e5 c5 4. c3?! (4. dxc5!) {White should realize this is not a French and initiate the exchange while they still can, forcing e6} Nc6 5. Nf3 cxd4 {else White can take and try to hold onto the extra pawn} 6. cxd4 Bg4 7. Be2 e6

```

One flawed idea in the Apocalypse attack for White is to gain the Bishop pair with 5.Bb5?! almost no matter what Black played, for example :

```
[Title "What White should probably not do"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1. e4 c6 2. Nf3 d5 3. exd5 cxd5 4. Ne5 Nc6 5.Bb5?! Bd7 6. Nxd7 Qxd7

```

If anything, Black can dodge that trade by playing Nd7, but they really aren't bothered by it at all, they are willing to trade their Light square Bishop for White's King's Knight in the first place, White is really doing them a service spending their own moves making it happening.

Instead, the correct main idea of the apocalypse attack, is that Black cannot move their light square Bishop out of the pawn chain for a long time or at all, and might end up being forced to play a position that looks more like a French. Whenever Black plays Bf5, White instinct should be to look at Qf3, threatening f5, f7, d5, and sometimes even b7. For example :

```
[Title "The apocalypse"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1. e4 c6 2. Nf3 d5 3. exd5 cxd5 4. Ne5 Bf5?? (4... a6 5.d4 Bf5? 6.Qf3! e6 (6... Bg6 7.Qb3) 7.Bd3) {more accurate than starting with Bb5+} 5.Qf3 e6? {not the best move, but other ones are still losing} 6. Bb5+ {White is winning}

```

When Black does fall for one of these traps as players new to the Caro-Kann often do, all hell breaks loose, hence the name of the opening.

But even knowing not to fall into these traps it is still difficult for Black to develop a plan.

If they capture the e5 knight prematurely, they get the worse of both the French and the Caro-Kann, with a very annoying pawn on e5 but no Knight able to target it, and still no good way to get their Queen's Bishop out. For example :

```
[Title "The worse of both world for Black"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1. e4 c6 2. Nf3 d5 3. exd5 cxd5 4. Ne5 Nd7 5. f4 {d4 is also playable and the stereotypical move, but if Black is to take on e5, recapturing with the f pawn and then playing d4 is even better. Black shouldn't capture on e5, but by playing Nd7, they either intend to or are giving White enough time to play both f4 and d4} Nxe5 6.fxe5 e6 {Black still has to worry about Qf3, and cannot play Bf5} 7.d4 {now Black has no good square for their King side pieces either and have to worry about moves like Qg4 and Bd3}

```

Finally, if they first develop both their knights, as they probably should, playing Bf5 is still risky if White went Nc3 as White can now throw g4 and g5. For example :

```
[Title "more spooky stuff"]
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1. e4 c6 2. Nf3 d5 3. exd5 cxd5 4. Ne5 Nf6 5. d4 Nc6 6. Nc3!? Bf5 7.g4 {and Black's Bishop has no option but to go home on d7, and Black has to worry about g5}

```

---
Tags: opening, caro-kann, 1.e4
---


title: Why is bxc5 better than b5?

text:
# Question
Title: Why is bxc5 better than b5?
```
[fen "rn3rk1/pp3ppp/3b2q1/2p1p3/1PP3b1/3P1N2/P3BPPP/1RBQR1K1 w - - 1 13"]

```

According to me, b5 is a pretty okay option, but according to Stockfish 10+ WASM, (Lichess) the advantage drops from +3.7 to +1.6. Why is this? Is it because it allows a3 and the potential opening up of the rook? But can’t I just go b6 in response (somehow, two innocuous pawn moves transform it to -0.6)? Lichess tells me it is a BLUNDER. WHY?

Why is bxc5 so good? According to me, after Bxc5, Black’s dark squared bishop is in an extremely active and attacking square, also pinning my f2 pawn to the king.

# Answer
bxc5 wins a pawn on the spot. After Bxc5 white replies Nxe5 forking queen and bishop and any pressure black had on the kingside is gone. With the bishop attacked 3 times (by knight, bishop and queen) black is forced to play Bxe2.

Add to that the fact that the b7 pawn is also en prise although white has to bear in mind Bb6 cutting off the rook's retreat.

```
[fen "rn3rk1/pp3ppp/3b2q1/2p1p3/1PP3b1/3P1N2/P3BPPP/1RBQR1K1 w - - 1 1"]

1. bxc5 Bxc5 2. Nxe5 Bxe2 3. Rxe2

```
> 6 votes

# Answer
I think that even if it was not for the e5 weakness and the tactics, b5 was still bad. Because you close lines rather then open them for your queenside game. It will take ages to push the a pawn and create tension again and exchange pawns -- if at all possible. The point of b4 is to exchange pawns and open the b file. As simple as that!
> 3 votes

---
Tags: analysis
---


# Question
Title: Is there a position where the weaker side can force stalemating the stronger side?
Usually, the (materially) stronger side stalemates the materially weaker side. Is there a position where the weaker side can forcibly stalemate the stronger side?

The only position I know where this happens is not forced, as White can choose to lose the pawn or go for the repetition instead.

```
[Title "White to move"]
[FEN "K7/P1k5/8/8/8/8/8/8 w - - 0 1"]

```

# Answer
> 9 votes
```
[FEN "8/8/8/3p4/1ppp4/prrp1K2/nqpp4/nbbk4 w - - 0 1"]

1. Kf2

```

---
Tags: endgame, draw, stalemate
---


# Question
Title: How do you remove the annoying bishop on h3?
I got this game today (Me white):

```
[fen "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]

1. e4 d5 2. Nc3 e6 3. exd5 exd5 4. d4 h6 5. Be2 Nf6 6. Nf3 Bd7 7. O-O Qc8 8. Bf4 Bd6 9. Bxd6 cxd6 10. b3 Bh3 11. Re1 O-O 12. Nh4 g5 13. Nf3 Qg4 14. g3 h5 15. Nd2 Qf5 16. Bxh5 Re8 17. Rxe8+ Nxe8 18. Qe2 Nc6 19. Bf3 Nxd4 20. Qd1 g4 21. Bxd5 Rc8 22. Ndb1 Nf3+ 23. Bxf3 gxf3 24. Nd5 Qe6 25. Qxf3 Rxc2 26. Ne3 Rc1+ 27. Nd1 Qe1# 0-1

```

The question is, how should I have gone about removing that pesky black light squared bishop without losing any material or weakening the king? As you will notice on move 11, Ng3 is stopped, and I don’t really have any ideas because Queen on c8 protects it heavily.

EDIT: I got a similar (almost identical) position just now! The difference was that gxh3 isn’t allowed. I played White.

```
[FEN ""]

1. e4 e5 2. Nc3 { C25 Vienna Game } d6 3. Nf3 Bg4 4. Be2 Nf6 5. O-O d5 6. Nxd5 Nxd5 7. exd5 Qxd5 8. c4 Qe6 9. Re1 c5 10. Rb1 Bd6 11. d3 O-O 12. b4 Qg6 13. b5 Bh3 14. Bf1 Re8 15. Ng5 e4 16. Nxh3 Nd7 17. Bf4 Bxf4 18. Nxf4 Qg5 19. Nd5 Re6 20. Nc7 Rg6 21. Nxa8 e3 22. Rxe3 Ne5 23. Qe1 f6 24. Qa5 Nf7 25. Qxa7 f5 26. Re8# { White wins by checkmate. } 1-0

```

# Answer
I had a suspicion (which stockfish confirmed) that weakening the kingside pawn structure is actually the best way to go about this, because black has no real attack here. After 10...Bh3, Stockfish recommends 11.Nb5, and gives white a +4 or so score. This fixes your hanging night on c3. It also puts Black on the defensive, threatening a devastating King Queen fork on g6. Black's best response is to castle. From there, black's pieces aren't developed enough to put together a strong attack, especially if white moves the queen onto the third row, pushing the black queen back.

```
 [Variant "From Position"]
 [FEN "rnq1k2r/pp3pp1/3p1n1p/3p4/3P4/1PN2N1b/P1P1BPPP/R2Q1RK1 w kq - 0 1"]

 1. Nb5 O-O 2. gxh3 a6 3. Na3 Qxh3 4. Qd3 Nc6 5. c3 Ng4 6. Rfe1 Rae8 7. Bf1 Qh5 8. Nc2 Re6

```

As a note, Stockfish finds Nb5 to be far and away the best move in this position. All other moves put black about even with white.
> 11 votes

# Answer
You should have taken the bishop at the first sensible opportunity which was after you played Re1 and your opponent played O-O. The Re1 move is important because after Qxh3 it allows you to play Bf1 driving the queen away. If Qg4+ then you play Bg2 and your king is relatively safe and you are a piece up.

```
[fen "rnq2rk1/pp3pp1/3p1n1p/3p4/3P4/1PN2N1b/P1P1BPPP/R2QR1K1 w - - 1 1"]

1. gxh3 Qxh3 2. Bf1 Qg4+ 3. Bg2

```

It's worth also noting that your move 10. b3 blunders your knight on c3. The move serves absolutely no purpose. You no longer have a dark squared bishop to fianchetto and, moreover, you have just made your backward c pawn weak. Positionally it is your c pawn which belongs on c3 and not your b pawn on b3.
> 8 votes

# Answer
That's simply a free bishop. gxh3 is how you remove the bishop because now you're up a piece. If you're worried about your king being opened up, notice that you have a sturdy knight on f3, bishop on e2 (that can immediately bounce around via f1 to g2, defending the g file), and possibly even a queen defending your kingside. There's no issues there.

The real problem is that this entire game you were hanging your c3 knight. Qxc3 from your opponent was a much scarier threat than the bishop sitting on h3.
> 7 votes

# Answer
The last moment I see where you had a good chance was when you took the pawn with your queen. It did keep your forward knight protected, but that was too far into enemy territory and wasn't doing much good and that move left your back row undefended for the coming attack. You could have instead moved the knight to F4 where it forks the queen and bishop and is protected by one of your pawns. That also leaves your queen defending the back row and hopefully lets you move your other knight out soon so your rook on a1 can join in the fun.

*edit* \- I just checked the analysis on chess.com and that is the turning point. Black could actually have just moved their queen down to checkmate you on the next move. Chess.com's analysis prefers moving your knight on b1 out to c3 to protect your forward knight and open up your rook which also defends the c file from the black rook since the knights are protecting each other. It also prefers pawn to c4 which accomplishes those last two goals as well, then proceeds with knight to f4 on the following move.
> 1 votes

---
Tags: bishops, defense
---


# Question
Title: Best "average centipawn loss" of all times?
I've found "average centipawn loss" calculated for some recent World Championship games, for example Magnus Carlsen vs Ian Nepomniachtchi, 2021 World Chess Championship.

Is there some "acl" calculation for other World Champions throughout chess history?

Who was the best ever "computer", the ultimate question...

# Answer
> 7 votes
Magnus Carlsen's moves are the ones most likely to match a computer's.

In some ways this isn't surprising. After all, chess playing strength has increased over time; Carlsen can learn from Kasparov, Fischer, Capablanca et al, but not vice versa.

# Answer
> 6 votes
I did some comparison, but this is old. See ThinkerJudge in my github repository.

There are scripts there that you can use to create new analysis with latest stockfish.

**Features**

A. Average error in centipawn (low is better) per game
B. Overall average error in centipawn (low is better)
C. Move Number with 50 to 100 cp error from a playable position (-50/50) cp, (high or None is better)
D. Move Number with 101 to 300 cp error from a playable position (-50/50) cp, (high or None is better)
E. Move Number with 301 to 500 cp error from a playable position (-50/50) cp, (high or None is better)

I ran the calsen/nepomniachtchi match with stockfish 15. See plot below.

Do not interpret this plot as comparing player's error from different years. But you can compare players from same year. For example carlsen 2021 vs nepomniachtchi 2021, or Fischer 1972 vs Spassky 1972 and others.

Feature C table.

```
C. Move Number with 50 to 100 cp error from a playable position (-50/50) cp, (high or None is better)
+-----------+------------------+-----------+------------------------+
|   GameNum | Nepomniachtchi   | Carlsen   |   Nepomniachtchi_score |
+===========+==================+===========+========================+
|         1 | None             | 27        |                    0.5 |
+-----------+------------------+-----------+------------------------+
|         2 | None             | 17        |                    0.5 |
+-----------+------------------+-----------+------------------------+
|         3 | None             | None      |                    0.5 |
+-----------+------------------+-----------+------------------------+
|         4 | None             | 18        |                    0.5 |
+-----------+------------------+-----------+------------------------+
|         5 | None             | None      |                    0.5 |
+-----------+------------------+-----------+------------------------+
|         6 | 52               | None      |                    0   |
+-----------+------------------+-----------+------------------------+
|         7 | None             | None      |                    0.5 |
+-----------+------------------+-----------+------------------------+
|         8 | None             | None      |                    0   |
+-----------+------------------+-----------+------------------------+
|         9 | None             | None      |                    0   |
+-----------+------------------+-----------+------------------------+
|        10 | None             | None      |                    0.5 |
+-----------+------------------+-----------+------------------------+
|        11 | None             | None      |                    0   |
+-----------+------------------+-----------+------------------------+

```

ThinkerJudge's **feature C** tells us which player commits mistake first, how much error from a playable position and what move number. From the table above in **game 1**, Carlsen commit mistake first at move number 27. This error is in the range 50 to 100 CP, from a playable position +/- 50 CP. If it is None that means the player had not made a mistake in the range 50 to 100 CP from a playable position +/- 50 CP.

That **table C** is based from Stockfish 15 analysis at **5 sec per position** on 4 threads using i7-2600K 3.4 Ghz 4-core processor.

Looking at the game analysis, the computer suggestion and evaluation is this.

```
27. Re3 { -0.24/27 } ( 27. Re3 { -0.24/27 } ) 27... Kf8 { -0.25/26 } ( 27... g6 { 0.26/30 } )

```

The actual move is `Kf8` with an evaluation of -0.25 pawn unit. Score is from `side to move` point of view or (SPOV), meaning after Kf8 black is slightly inferior. The computer suggested `g6` with a positive score favoring black.

`Error = 0.26 - (-0.25) or 0.51 pawn unit or 51 CP (centipawn) unit.`

That result is within the condition specified in Table C feature.

```
C. Move Number with 50 to 100 cp error from a playable position (-50/50) cp

```

---
Tags: engines, history, world-championship
---


# Question
Title: What is the idea behind the Nd7 Nb6 by black maneuver in the King's Indian Defence?
I have seen this idea often and want to know the idea behind it.

White can create a doubled pawn weakness on b7 and b6 by doing Bxb6, but then would black have control over f4 and also c5? (unless some a3 b4 comes?).

What is the exact motivation/plan of this maneuver? How do I react after Bxb6 cxb6?

It would be great if there is any material (videos, books, blogs, or anything) which talks about this plan

```
       [FEN ""]
       1. d4 Nf6 2. c4 g6 3. Nc3 Bg7 4. e4 d6 5. Nf3 O-O 6. h3 e5 7. d5 a5 8. g4 Na6 9. Be3 Nd7 10. a3 Nb6

```

# Answer
Well for starters, Bxb6 is a bad move for white because the bishop on e3 is a key piece in white's position. Notice that all of white's pawns are fixed on light squares. If you give up the dark squared bishop so easily, then you'll get killed by a knight on c5, a bishop on f4, a queen on h4, etc. Moreover, your remaining bishop currently on f1 becomes a lot worse if you can no longer push the light squared pawns to dark squares. So Bxb6 is unthinkable unless you're winning something serious immediately (I wouldn't even do it if I was winning a pawn).

Finally, you say "white will create a doubled pawn weakness" with this move, but doubled pawns are only bad if they can become targets. Notice how the b file is closed, so no rook can ever attack those pawns. White just traded their dark squared bishop, so no way to attack the b pawn with a bishop either. Actually, with the semi-open c file, now it's black's turn to target the backwards c4 pawn. The doubled b pawns actually give you even more avenues for your pieces than if the pawn remained on c7!

Now are there any positives to Nb6 in of itself? Sort of. One problem in black's position is that there are too many pieces for too few squares. Both of your knights want to use c5 for instance. Your bishop and knight want to use d7. etc. So black is truly looking to get in some trades---any trades. Nb6 allows Bd7+Nc5+Nba4 finally trading the b6 knight for the c3 knight. If this can be achieved, then black finally has solved their lack of space issue. Is this slow? Incredibly slow. This is probably why the position is not so good for black overall. However, in closed/locked positions like this, you have more time for maneuvers like this, so the plan is possibly not too slow.

Natural moves from white will therefore be too slow in response to this plan. The real question is: can white do something scary on the kingside, while black uses a lot of tempi on the queenside to achieve a simple piece trade?

```
[FEN "r1bq1rk1/1pp2pbp/nn1p2p1/p2Pp3/2P1P1P1/P1N1BN1P/1P3P2/R2QKB1R w KQ - 1 11"]

1. Rg1 (1. Bxb6? cxb6 {Now black has complete control over the dark squares in the position. With Nc5 and/or Bh6 coming next, black is already probably for choice.}) Bd7 2. h4! {An important move - going for black's king immediately.} Nc5 3. a4! {Taking one time out to stop black's maneuver. White is for choice now that black's idea has been stopped, and the kingside attack rages on with g5+h5+etc} (2. Be2?! Nc5 3. Rb1? {Better than Rc1 which will run into an eventual fork, but simply too slow. Black now achieves everything they want for free.} Nba4! 4. Nxa4 Bxa4 5. b3 Bd7 {and black is for choice with an uncramped position.})

```
> 10 votes

---
Tags: opening, strategy, theory, kings-indian
---


title: Chess Engine API

text:
# Question
Title: Chess Engine API
I am writing a C# 3D chess game in Unity. I am looking for a chess engine that can

1. Take in an FEN string
2. Return the best move to make given this FEN
3. Check if the board given this FEN is in checkmate

Does anyone know of a chess engine that can do this, preferably in C#? I have tried Stockfish and other chess engines, but they all work from the command line. If anyone knows how I can program the game using an engine that works from the command line, that would also work. Thanks!

# Answer
Unfortunately, chess engine doesn't work like what you expect. In particular, there is no such thing as API in the chess engine world. That's because calculating a chess move takes time, and it'll be insane to block your function call until you can get the move.

Chess engine almost always do the works in its own thread or process. You might need to learn how to interact with a thread/process. You'll also need to learn UCI chess protocol. I don't think there is a wrapper for you, but maybe there is just that I don't know.

Stockfish is a C++ engine, so you might need to wrap it with a managed C++ layer for C#. There is a Stockfish port on C#, but it's not as good as the original. However, you don't even need a source code to do your works. You could also take a closed engine such as Houdini.

General steps:

1. Download a compiled binary (\*.exe). It can be anything like Houdini, Komodo or Stockfish. You don't have to compile the source code yourself.
2. Use Process.Start in C# to start a process of the chess engine
3. Talk with the child process like here
4. Try to send a UCI message like this:

> isready

The isready UCI command is like pinging the chess engine. You should hear something back if your implementation works. Please take a look at the UCI documentation, you'll find it on Google. Once you know your code works. Try this:

> ucinewgame
>
> go move time 1000

This gives the engine one second to make a move. You will get something like this:

> bestmove e2e4 ponder e7e5
> 1 votes

# Answer
I know of two APIs by which you can access Stockfish. The source code is available for both to implement yourself. In one case, the API is also hosted and can be queried freely.

# noobpwnftw/chessdb

I discovered this API through Fabian Fichter’s answer to this similar, later question.

The front-end is a PHP script and uses in addition MongoDB. It requires a Redis-compatible server for data storage. See the source code on GitHub.

The API is actively hosted and can be freely queried. For example, here’s a position from the Fried Liver Attack, with the FEN: “r1bqkb1r/ppp2ppp/5n2/n2Pp1N1/2B5/8/PPPP1PPP/RNBQK2R w KQkq - 1 6”

```
r1bqkb1r/ppp2ppp/5n2/n2Pp1N1/2B5/8/PPPP1PPP/RNBQK2R w KQkq - 1 6

```

For example, to find just the best move, form the query like:

```
https://www.chessdb.cn/cdb.php?action=querybest&board=FEN_STRING_WITH_BLANKS_ESCAPED

```

In this case:

```
https://www.chessdb.cn/cdb.php?action=querybest&board=r1bqkb1r/ppp2ppp/5n2/n2Pp1N1/2B5/8/PPPP1PPP/RNBQK2R%20w%20KQkq%20-%201%206

```

which gives you this result:

```
move:c4b5

```

which translates to Bb5+, agreeing with theory.

See the GitHub link for a little additional documentation, such as using `querypv` to get continuations.

## Ilya Zhelyabuzhsky’s Python wrapper for Stockfish

See Ilya Zhelyabuzhsky’s Python wrapper (a) on GitHub and (b) available for installation from PyPI.

This requires that Stockfish be installed on the server.

This Python package implements a class to integrate Stockfish with Python.

For example, you can define a position from a FEN and then request the best move:

```
stockfish.set_fen_position("rnbqkbnr/pppp1ppp/4p3/8/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2")
stockfish.get_best_move()

```

See either of the above links for additional documentation.
> 0 votes

---
Tags: engines, fen
---


title: Chess engine with API

text:
# Question
Title: Chess engine with API
I am looking for a chess engine which provides a normal API which I can use with some high level programming language like C# or python. I went through the list of leaders (Houdini, Komodo, Stockfish and Rybka) and was not able to find any signs that these engines provides API (which surprised me and suggested that I am missing something).

To be less vague, here is what I need from this API:

* be able to load specific game into the engine
* be able to evaluate position of the game
* be able to make a move

So, does anyone knows an engine which provides a clear API to it's functions?

# Answer
As others have said, UCI is the API you want. The full specifications of the protocol is here (the zip file extracts to a text file): http://download.shredderchess.com/div/uci.zip

It's actually very straight forward and simple, a UCI engine must respond to and reply in plain text through stdin, stdout and stderr. In fact, you should be able to launch the executable binary of any UCI engine on your platform and issue the UCI commands manually.

UCI facilitates instructions from a GUI or other engine to tell the specific engine to do whatever it is that you want it to do, including analyse a specific PGN file (the loading of it is through the GUI or similar front-end, the raw moves are then fed to the engine in extended algebraic form, such as e4 becoming e2e4). The second and third points of your requirements are standard with UCI, but it is up to each engine developer to support them (given how lean those requirements are, that should be most of them).

Here's an example of UCI in action on the command line:

```
bash-3.2$ ./stockfish-5-64
Stockfish 5 64 by Tord Romstad, Marco Costalba and Joona Kiiski
uci
id name Stockfish 5 64
id author Tord Romstad, Marco Costalba and Joona Kiiski

option name Write Debug Log type check default false
option name Write Search Log type check default false
option name Search Log Filename type string default SearchLog.txt
option name Book File type string default book.bin
option name Best Book Move type check default false
option name Contempt Factor type spin default 0 min -50 max 50
option name Mobility (Midgame) type spin default 100 min 0 max 200
option name Mobility (Endgame) type spin default 100 min 0 max 200
option name Pawn Structure (Midgame) type spin default 100 min 0 max 200
option name Pawn Structure (Endgame) type spin default 100 min 0 max 200
option name Passed Pawns (Midgame) type spin default 100 min 0 max 200
option name Passed Pawns (Endgame) type spin default 100 min 0 max 200
option name Space type spin default 100 min 0 max 200
option name Aggressiveness type spin default 100 min 0 max 200
option name Cowardice type spin default 100 min 0 max 200
option name Min Split Depth type spin default 0 min 0 max 12
option name Threads type spin default 1 min 1 max 128
option name Hash type spin default 32 min 1 max 16384
option name Clear Hash type button
option name Ponder type check default true
option name OwnBook type check default false
option name MultiPV type spin default 1 min 1 max 500
option name Skill Level type spin default 20 min 0 max 20
option name Emergency Move Horizon type spin default 40 min 0 max 50
option name Emergency Base Time type spin default 60 min 0 max 30000
option name Emergency Move Time type spin default 30 min 0 max 5000
option name Minimum Thinking Time type spin default 20 min 0 max 5000
option name Slow Mover type spin default 80 min 10 max 1000
option name UCI_Chess960 type check default false
uciok
isready
readyok
quit
bash-3.2$

```

The commands I issued were uci, isready and quit.

To utilise the UCI commands you essentially have two main choices; you can use an existing interface (e.g. ChessX, Arena and a host of others) or you can write your own code to issue instructions to an engine or group of engines. I believe there may already be Python wrappers for accessing UCI engines, but I'd need to double-check. There's definitely python-chess (import chess) and pychess (import pychess), I just can't recall the extent of their functions. I can't recall where pychess is lurking (probably github or google code), but python-chess can be installed with pip.
> 10 votes

# Answer
python-chess provides a useful API and supports UCI, apparently:

http://python-chess.readthedocs.io/en/v0.15.3/uci.html?highlight=engine

The above link gives a 'stockfish' example.
> 4 votes

# Answer
I've googled on "chess engine api" but have not seen any real API's. As suggested in the comments of your question I would go with UCI. This is also the way GUI's communicate with chess engines.

If you're really a hardcore programmer you could always check out the open source engine Stockfish. It could very well be that there is some sort of API built in it, or you could make a clone and build your own API for it.

http://stockfishchess.org/
> 3 votes

# Answer
Batch First is a JIT compiled chess engine written in Python, compiled using Numba, which would allow easy C++ interfacing and even easier Python interfacing.

While Batch First itself is an engine not API, it heavily uses and relies upon the Python-Chess package, which is an awesome API.

The JIT compilation of Batch First, and use of NumPy arrays for representing boards, allows a more practical Python interface (at least an order of magnitude faster) for actual use in a chess engine.

The core of the engine is a zero-window k-best-first search algorithm used to evaluate ANNs in batches.

Full disclosure, I am the author of the Batch First engine.
> 1 votes

# Answer
I know of two APIs by which you can access Stockfish. The source code is available for both to implement yourself. In one case, the API is also hosted and can be queried freely.

(This answer is essentially the same as this answer that I gave to a similar, later question.)

# noobpwnftw/chessdb

I discovered this API through Fabian Fichter’s answer to this similar, later question.

The front-end is a PHP script and uses in addition MongoDB. It requires a Redis-compatible server for data storage. See the source code on GitHub.

The API is actively hosted and can be freely queried. For example, here’s a position from the Fried Liver Attack, with the FEN: “r1bqkb1r/ppp2ppp/5n2/n2Pp1N1/2B5/8/PPPP1PPP/RNBQK2R w KQkq - 1 6”

```
r1bqkb1r/ppp2ppp/5n2/n2Pp1N1/2B5/8/PPPP1PPP/RNBQK2R w KQkq - 1 6

```

For example, to find just the best move, form the query like:

```
https://www.chessdb.cn/cdb.php?action=querybest&board=FEN_STRING_WITH_BLANKS_ESCAPED

```

In this case:

```
https://www.chessdb.cn/cdb.php?action=querybest&board=r1bqkb1r/ppp2ppp/5n2/n2Pp1N1/2B5/8/PPPP1PPP/RNBQK2R%20w%20KQkq%20-%201%206

```

which gives you this result:

```
move:c4b5

```

which translates to Bb5+, agreeing with theory.

See the GitHub link for a little additional documentation, such as using `querypv` to get continuations.

## Ilya Zhelyabuzhsky’s Python wrapper for Stockfish

See Ilya Zhelyabuzhsky’s Python wrapper (a) on GitHub and (b) available for installation from PyPI.

This requires that Stockfish be installed on the server.

This Python package implements a class to integrate Stockfish with Python.

For example, you can define a position from a FEN and then request the best move:

```
stockfish.set_fen_position("rnbqkbnr/pppp1ppp/4p3/8/4P3/8/PPPP1PPP/RNBQKBNR w KQkq - 0 2")
stockfish.get_best_move()

```

See either of the above links for additional documentation.
> 1 votes

# Answer
Here there's a port version of Stockfish in .Net: https://github.com/bpfliegel/Portfish

To use this engine (once it's compiled), you'll nedd a GUI like Arena http://wwww.playwitharena.com or ScidVSPC http://scidvspc.sourceforge.net. These applications are used to provide a nice interface and allow you to load games/positions, analyze them (I'm pretty sure you can load a game on pgn and analyze it by an engine with criteria like "n seconds per move" or "n plies per move"), run matches between engines, etc

In (almost) every chess engine you should find something like a uci.cs or an xboard.cs file which is commited to this communication task.

(A "chess engine" is a program that is capable of playing chess but has no graphical interface. The way it communicates to applications like Arena or ScidVSPC is by the UCI or xboard protocols. Most of the chess programs are written this way, so the developer can forget about the GUI stuff and focus on the "brain").
> 0 votes

# Answer
I was looking around for something similar and came across Joe's Chess API:

http://chess-api.herokuapp.com/
> 0 votes

---
Tags: engines, programming
---


# Question
Title: When was the first engine vs engine match?
I came across this game in Gerald Abrahams book *The Chess Mind*, 1968 edition:

```
[fen ""]
[Title "USSR Computer vs USA Computer, March 1967"]

1. e4 e5 2. Nf3 Nc6 3. Nc3 Bc5 4. Nxe5 Nxe5 5. d4 Bd6 6. dxe5 Bxe5 7. f4 Bxc3+ 8. bxc3 Nf6 9. e5 Ne4 10.Qd3 Nc5 11. Qd5 Ne6 12. f5 Ng5 13. h4 f6 14. hxg5 fxg5 15. Rxh7 {The first ever engine sacrifice?} Rf8 16. Rxg7 c6 17. Qd6 Rxf5 18. Rg8+ Rf8 19. Qxf8#

```

According to Abrahams this was:

> The third game of a match in which the first two were drawn

So, this wasn't the first engine match although it may have been the third.

# Answer
According to Wikipedia:

> Kotok-McCarthy also known as *A Chess Playing Program for the IBM 7090 Computer* was the first computer program to play chess convincingly. It is also remembered because it played in and lost the first chess match between two computer programs.

Leaving aside the inconsistency between being "the first computer program to play chess convincingly" and losing the first computer match, it looks like this match was the first.

The article continues:

> In 1965, McCarthy, by then at Stanford University, visited the Soviet Union. A group using the M-2 computer at Alexander Kronrod’s laboratory at the Moscow Institute for Theoretical and Experimental Physics (ITEP) challenged him to a match. Kronrod considered Kotok-McCarthy to be the best program in the United States at the time.
> ...
> Georgy Adelson-Velsky, Vladimir Arlazarov, Bitman, Anatoly Uskov and Alexander Zhivotovsky won the correspondence match played by telegraph over nine months in 1966-1967. The Kotok-McCarthy program lost the match by a score of three to one

So, it looks like the very first engine vs engine game was played in 1966. The game given in the question was the third of four and the US computer engine, Kotok-McCarthy, drew two and lost two.
> 5 votes

---
Tags: engines, history
---


title: Chess and aging

text:
# Question
Title: Chess and aging
Chess playing strength, like IQ, is a multifaceted thing. To my best knowledge, it's at least commonly agreed that when aging, you rather lose tactical attentiveness than positional understanding. I now could go endlessly into other facet details (Müller/Engel player types being influenced differently; risk avoidance; time management etc.) but since I shall only ask one question: Do you know of psychological studies dealing with the influence of aging on chess? (Generic aging/mental ability studies would be OK too if directly applicable to chess.)

Obviously, this is relevant for training.

# Answer
> 9 votes
Sources taken from chessjournal article: https://www.chessjournal.com/does-age-affect-chess-ability/

# Answer
> 7 votes
Nikolai Krogius, Russian GM and sports psychologist, summarized the state of knowledge regarding chess and aging and described his own research in his 1976 book, Psychology in Chess.

First, he dismisses US research :-)

> In his dissertation, P. Buttenwisser (Stanford USA, 1935) advanced the opinion that a chess player preserves his optimal strength until the age of fifty. He came to this conclusion by analyzing the games of chess amateurs who did not participate in competitions regularly. For this reason Buttenwisser's findings cannot be regarded as convincingly demonstrated.

He is more impressed by the Soviet research of Stanislav Strumilin.

> More serious research on the connection between the age of a chess player and his achievements was carried out by Soviet Academician, Strumilin. In his book *Problems in the Economics of Labour* (Moscow 1925) he made a statistical analysis of the results of 43 matches (1863 - 1911) and of 34 international tournaments (1890-1914). The participants in these competitions were divided into several age groups. Strumilin counted the total number of games played and then wins, losses and draws, and then compared the results for different age groups. He concluded that a chess player reached the peak of success between the ages of 32 and 33, after which there was a sharp fall in results, while after the age of 60 there was a catastrophic fall in the player's mental energy.

Krogius then describes his research into the subject. He differs from Strumilin, who considered wins, loses and draws, in that he considered tournament standings as more important. He examines the records of 32 great players ranging in time from Chigorin and Tarrasch through to Bottvinnik, Bondarevsky, Kotov and Boleslavsky and 125 tournaments from 1881 to 1967.

His results:

> A chess player attains his best results at about the age of 35: his period of optimal and consistent results lasts somewhat longer than 10 years; it ranges between the ages of 30 and 40; some decrease in strength is observed usually around the age of 43 and a particularly noticeable decline starts at the age of 47.

---
Tags: reference-request, aging
---


# Question
Title: What does the "GMS" abbreviation mean here?
I was wondered what the abbrevation meant here. https://ratings.fide.com/profile/2027895/chart

"Period RTNG GMS RAPID RTNG RAPID GMS BLITZ RTNG BLITZ GMS"

From the context it seems a odd for it to mean Grandmasters.

# Answer
> 4 votes
That's an abbreviation for "games". 0 means the player was inactive (no rated games played).

---
Tags: fide, rating, terminology
---


# Question
Title: If players are not writing their moves, can they claim a draw using the threefold repetition rule in an USCF or FIDE 30+0 chess tournament?
It is my understanding that the USCF expresses that if a player has less than 5 minutes in a 30+0 game, neither the player nor his/her opponent have the obligation to continue with chess notation.

If players are not writing their moves can they claim a draw using the threefold repetition rule in an USCF or FIDE 30+0 chess tournament?

***Do the arbiters have the obligation to write the moves when players are not doing it?***

If the arbiter notices that a position has been repeated three times should they intervene if the players do not claim a draw?

What do the USCF and FIDE rules express about these situations?

P.S. What Is The Threefold Repetition In Chess? The threefold repetition rule states that if a game reaches the same position three times, a draw can be claimed. A position is repeated if all pieces of the same kind and color are on identical squares, and all possible moves are the same.

I found a similar question: What are the different rules for claiming a draw?

However, that was several years ago. Also, I am interested in specific in 30+0 games.

---

***Update: USCF rules are available online for free***

Here is the link:

https://www.uschess.org/index.php/Official-Rules/US-Chess-Rulebook-The-Official-Rules-of-Chess-7th-Edition-Tim-Just-Chief-Editor.html

---

***Update for USCF: 14K. Director declares draw for lack of progress.***

If one or both of the following occur(s) then the TD may declare the game drawn:

1. The same position has appeared, as in 14C, for at least five consecutive alternate moves by each player.
2. Any consecutive series of 75 moves have been completed by each player without the movement of any pawn and without any capture. If the last move resulted in checkmate, that shall take precedence

---

***Update for USCF: 14F4. Director may count moves in sudden death.*** In sudden death, a player with fewer than five minutes remaining and a simplified position in which no pawn moves or captures seem likely may stop both clocks, declare to a director an intention to invoke the 50-move rule when possible, and ask for assistance in counting moves. A director who agrees this is appropriate may count moves or use a deputy or a clock with a move counter to do so. a. If the director or the deputy will count moves, the count should begin by crediting moves already made and listed on the scoresheet of the player intending to claim. An opponent who believes a different number of moves have been made should present this case if and when the count reaches 50. b. The director or deputy may either keep score, make check marks, or combine the two. c. After the count by the director or deputy begins, neither player has a right to know the count until 50 moves are reached. At that point the game is declared drawn unless the opponent successfully challenges the move count. ***d. The opponent may challenge either the moves on the claimant’s scoresheet before the director/deputy count, the count itself, or both, but must have a scoresheet adequate (13C7) to support the challenge.*** e. If the challenge is upheld, the game shall continue with the director or deputy resuming from the corrected count. If the claimant’s scoresheet is responsible for the wrong count, two minutes shall be added to the remaining unused time of the claimant’s opponent. If the director/deputy count was wrong, there shall be no time adjustment. f. The director may insert a clock with a move counter that shows the remaining time of both players, set the move counter to zero, and order play to resume. When the clock indicates that both sides have completed 50 further moves, either player may claim a draw. If this method is used, the director should inform the players that if a move is erroneously not counted or double counted, the players should stop the clock and notify the director.

# Answer
> 4 votes
> Do the arbiters have the obligation to write the moves when players are not doing it?

In general, "No". In rapid (30+0 counts as rapid in the FIDE Laws) there is no obligation for anybody, neither players nor arbiters, to write the moves.

The only instance in which the arbiter or another person other than the player would write the moves for a player would be in case of -

1. Disability. For some reason the player cannot write the moves down.
2. In case of a standard time control with multiple controls where there is no increment in the control and it is not the last control and the player has less than 5 minutes left. The only place these ever happen is elite events.

> If players are not writing their moves can they claim a draw using the threefold repetition rule

There needs to either be a record of the game or the arbiter needs to be watching and paying attention. So, if the opponent is still recording because they have more than 5 minutes left then their scoresheet can be used to check the moves. If moves are being recorded electronically (live boards) then in some cases these can be used. Finally if the arbiter is watching and counting then they can verify the claim.

> If the arbiter notices that a position has been repeated three times should they intervene if the players do not claim a draw?

No. It is expressly forbidden. This would be interpreted as helping one of the players. There is an additional rule which says that if the arbiter sees that there have 5 repetitions then the arbiter MUST intervene and declare the game drawn.

---
Tags: rules, fide, tournament, uscf, arbiters
---


title: Finding all critical endgames

text:
# Question
Title: Finding all critical endgames
A winning position is called critical, if all moves - except one - draw or lose (assuming the opponent plays perfectly). Similarly, a drawn chess position is called critical, if all moves - except one - lose.

Consider this critical endgame position as an example.

```
[FEN "8/8/1B6/6P1/1b6/8/2K4k/8 w - - 0 1"]

```

The only winning move is 1. Ba5!! while every other move draws.

Using endgame tables it is possible to determine if a given position is critical. However, I am interested in a database with all critical endgames. Does such database exist? If not, how could I create one myself?

# Answer
> 2 votes
Partly building on ferdy's answer (and the comments to it). In Python this can be done as follows:

1. Using the `python-chess` module, iterate through the games in your database. Docs: https://python-chess.readthedocs.io/en/latest/pgn.html

https://python-chess.readthedocs.io/en/latest/core.html#board
2. Now you could use tablebases, but another option is to use Stockfish. Download the Stockfish engine, and then use the `stockfish` python module: https://pypi.org/project/stockfish/

For each position in a game, get its FEN (using `python-chess`), and then set the `stockfish` module object's position to it (using the `set_fen_position` method). Finally, call `get_top_moves(2)` with the `stockfish` object.

Then, a position can be deemed critical if:

a) The top move is winning (e.g., \>= +4 or \<= -4, for White's and Black's perspectives).

b) The second top move is under an evaluation that's winning (e.g., \<= +0.5 (White isn't winning) or \>= -0.5 (Black isn't winning)).

OR

a) The top move is at least around equal (e.g., \>= -0.5 (White is at least close to equal) or \<= +0.5 (Black is at least close to equal)).

b) The second top move is losing (e.g., \<= -4 (White is losing) or \>= +4 (Black is losing)).

# Answer
> 3 votes
Here is a typical procedure to save critical positions.

* For the given material configuration like kbpkb ... generate positions and save to FEN. To generate positions you can use python-chess library for example.
* Analyze the FEN with ending tablebase and save it if critical.

# Answer
> 2 votes
As posed, I think this is more of a “data structures and algorithms” question. I don’t think the chess content can be leveraged, except there are existing tables which can be mined.

In compositions, it’s not just a single critical position which is interesting - rather it’s a chain of critical positions where with “best play by Black”, there is at least one chain of mostly unique White moves that lead to a “clearly won/drawn” position.

If this line of thinking interests you, then there is definitely chess content, and there is also a clear retroanalytic approach to efficiently determine a sequence of critical positions.

In this case it may well be worth constructing your own tablebase to allow you to explore the possibilities, particularly the notions of “clearly won” and “best defensive play”.

Hope this helps: good luck!

---
Tags: endgame, tablebases
---


# Question
Title: What is Stockfish 15's FIDE calibrated Elo rating?
Elo rating only makes sense based on the population of players. So I wonder, has Stockfish's Elo been calculated in a pool including humans or human-calibrated engines?

Related: How accurate are chess engine ratings?

# Answer
Stockfish 15 is about 3620 rating on the FIDE scale. See the ratings in TCEC Cup 10 which played with a Stockfish that is slightly stronger than Stockfish 15.)

We can take the TCEC ratings as "FIDE ratings" because some time ago there was an effort to calibrate the TCEC ratings as such. They did this by benchmarking against Fritz in Bahrain, which was assigned Kramnik's elo rating at the time he played (and drew) that man vs. machine match.

Do remember that the rating of any engine compared to a human will depend on things like the hardware used, the time control, and so on. Ratings against other engines are straightforward in comparison.
> 4 votes

# Answer
Here is one approach to find the approximate stockfish's FIDE Elo.

1. Let Magnus play it at classical time control in a 24-game match.
2. What is the result? Let's say (1.5-22.5) in favor of Stockfish. Magnus got 3 draws. You can do your estimate here.
3. Since Stockfish has no FIDE Elo rating yet, FIDE may grant Stockfish a rating equal to the highest in the current rating list, and that is 2864. So now it will be Magnus (2864) vs Stockfish (2864).
4. Let's update the rating. rd = 2864 - 2864 = 0
In 24 games, the expected score is 12 or 50% of 24 games because the rd is zero.

```
rn = ro + K * (actual_score - expected_score)

where:
rd = rating difference
rn = new rating
ro = old rating
K = development coefficient, say 10
actual_score = 1.5 (Magnus), 22.5 (Stockfish)

```

```
rn_magnus = ro_magnus + K * (actual_score - expected_score)
rn_magnus = 2864 + 10 * (1.5 - 12)
rn_magnus = 2759

```

```
rn_stockfish = ro_stockfish + K * (actual_score - expected_score)
rn_stockfish = 2864 + 10 * (22.5 - 12)
rn_stockfish = 2969

```
5. Magnus played some games against humans and he got back to 2850
6. Magnus play a second match with stockfish for 24 games. It will be Magnus (2850) vs Stockfish (2969)
7. Let's say the result is (2.0 - 22.0) in favor of Stockfish, Magnus got 4 draws.
8. Let's update the new rating.

```
magnus_rd = 2850 - 2969 = -119
actual_score = 2.0
expected_score = 0.335 * 24 or ≈ 8
rn_magnus = ro_magnus + K * (actual_score - expected_score)
rn_magnus = 2850 + 10 * (2.0 - 8) = 2790

```

```
stockfish_rd = 2969 - 2850 = 119
actual_score = 22.0
expected_score = 0.665 * 24 or ≈ 16
rn_stockfish = ro_stockfish + K * (actual_score - expected_score)
rn_stockfish = 2969 + 10 * (22.0 - 16) = 3029

```
9. Do this many times until the gap between the highest human rating and stockfish rating reaches 700 or more.

At this moment rd = 3029 - 2790 = 239, this is far from 700, so a match with the engine is still reasonable.

Also Magnus can still gain some rating points against human opponents. So the approximate rating of Stockfish depends on the rating of the highest human player or top human players and how these players will perform against Stockfish.

Formula to get the approximate expected score given the rating difference.

```
expected_score ≈ 1 / (1 + 10 ^ (-rd/400))

```

We can build a simulator with some assumptions and stop the simulator when rd is 700 or more. Then get the final rating of Stockfish.
> 0 votes

---
Tags: engines, stockfish, elo, human-versus-machine
---


# Question
Title: How do I get the solutions of the puzzle using stockfish?
I have a list of PGN files that are games between top grandmasters where one player resigned at the end of the game. I am looking to find solutions to those position using stockfish/or another chess engine(programmatically). Ideally - I should be able to pass a PGN or FEN string and get the solution as the output.

How can I do that?

# Answer
In Python this can be done as follows:

Using the python-chess module, iterate through the games in your pgn database. Docs: https://python-chess.readthedocs.io/en/latest/pgn.html

https://python-chess.readthedocs.io/en/latest/core.html#board

Now to use Stockfish, download the Stockfish engine, and then use the stockfish python module: https://pypi.org/project/stockfish/. python-chess can also be used to interact with Stockfish, but I'm not familiar myself with how to do this.

For each position in a game (that you want to find the best move for), get its FEN (using python-chess), and then set the stockfish module object's position to it (using the set\_fen\_position method). Finally, you can call the `get_best_move` function of the stockfish module.
> 1 votes

---
Tags: stockfish, python
---


# Question
Title: Is The Four Knight Sicilian winning for White?
Consider this variation of the Four Knight Sicilian:

```
 [FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 1 0"]
 1. e4 c5 2. Nf3 e6 3. d4 cxd4 4. Nxd4 Nf6 5. Nc3 Nc6 6. Nxc6 bxc6 7. e5 Nd5 8. Ne4 Qc7 9. f4 Qb6 10. c4 Bb4+ 11. Ke2 f5 12. Nf2 Ba6 13. Kf3 Ne7 14. Qa4! c5 15. h4 O-O 16. Be3

```

I analyzed this position with Stockfish 14.1 NNUE for four iterations of 30 minute each. In the end, it appears winning for White. Does black have counterplay to avoid this line when playing the Four Knight Sicilian?

# Answer
> 9 votes
It isn't a main line, as Black struggles to equalize in the opening. But the Sicilian 4 knights isn't refuted/winning for White. In the variation you give, 15. .. O-O by Black is a blunder. Black should play Qc6+ according to my local Stockfish 15, depth 33, with an evaluation of 0.43. White is still better, but far from winning. So yes, Black **can and should** avoid your variation.

Furthermore, Black can play 8. ..Bb7, which Stockfish 15 likes better for Black at depth 41. (Full variation given by SF15, move 8 on depth 41: 8...Bb7 9.Be2 c5 10.O-O Qc7 11.Nd6+ Bxd6 12.exd6 Qc6 13.f3 c4 14.Qd4 O-O 15.Bxc4 Rfc8 16.b3 Qxd6 17.Bd2 a5 18.Rfd1 Qb6 19.Qf2 Qxf2+ 20.Kxf2 Ne7 21.Bd3 Ba6 22.c4 d5 23.Rac1 a4 24.Bb4 Nc6 25.Bd6 axb3 26.axb3 dxc4 )

# Answer
> 0 votes
*Is the Four Knight Sicilian winning for white?*

Probably not, but white can get something. Not with 14. Qa4?, which allows 14...g5!. Better is 14.Be3, but black will later play ...c5 and ...Bb7 and then he prepares ...e5 or ...g5. He can equalize.

My favorite is 12.exf6! Nxf6 13.Be3. After 13...Qd8 White can grab the bishop pair with 14.Nd6+, later play Rg1 and g4. If 13...Qc7 or 13...Qb8 (protecting d6), then 14.Nxf6 gxf6 15.Kf2 and the white king is placed better than the black. White has a lasting slight advantage, and he risks less than in the 12.Nf2 lines, where black has a bunch of tricks.

The 8...Bb7 line has been discussed in a few Top GM games. In the main line white gets the bishop pair, and in my opinion black has not yet shown how to fully equalize against it.

---
Tags: opening, analysis, sicilian-defense
---


title: Pinned piece chain

text:
# Question
Title: Pinned piece chain
How long a "Pinned piece chain" can you make? Here a "Pinned piece chain" is a chain of pieces where each is pinned by the last.

Here for example is a chain of length 3. The knight is pinned by the queen, which is pinned by the rook which is pinned by a another rook.

Also, is it possible for ALL the non king pieces to be pinned?

# Answer
> 3 votes
You can take the idea from your example and add one more pin by putting the pieces closer together and shifting them down so that it becomes possible to pin the last pinning rook:

Then you have four pinned pieces, using a diagonal and a rank/file per king. Intuitively, I don't expect it will be possible to have a longer chain, but I'd love to see a counterexample!

Regarding the second part of the question, yes, it is possible for all the non-king pieces to be pinned. Not a very exciting example, but imagine the two kings and a rook of each color all on a single file, so that the rooks pin each other:

I can't think of a way of doing this with more than two pieces.

---
Tags: problems, pins
---


# Question
Title: Why after 1. d4 Nf6, 2. c4 is so common but after 1. c4 Nf6, 2. d4 is so rare?
I am using Lichess's master database and after 1. d4 Nf6, 71.63% of the game continues with 2. c4. However, after 1. c4 Nf6, only 5.22% of the game continues with 2. d4. Are they not essentially the same opening?

My question is:

Why after 1. d4 Nf6, 2. c4 is so common but after 1. c4 Nf6, 2. d4 is so rare? Is it more because of some psychological reasons, or is it because after 1. c4 Nf6, moves such as 2. Nc3, 2. g3 and 2. Nf3 are objectively better than 2. d4?

# Answer
To answer your question, I think it mainly comes down to selection bias. The White players of the games after 1.c4 Nf6 are often not intending to play a Queen's pawn opening (at least, not right away with 2.d4). I'll go into why in the rest of this answer.

If you wanted to play the position after 1.d4 Nf6 2.c4, there's (almost) no good reason to not start with 1.d4. Starting with 1.c4 gives Black the opportunity to play 1...e5 or 1...c5 (both highly respectable systems), and now you're stuck in an English.

After 1.d4, the main downside I can think of is that it allows the QGA (1.d4 d5 2.c4 dxc4). I think it'd be fairly odd to play 1.c4 just to avoid the QGA, but I'm sure there are some players out there who do this.

Note that the 1.c4, 2.d4 move order does not have the benefit of avoiding the QGD. After 1.c4 Nf6 2.d4, 2...e6 gives Black the option to follow up with 3...d5, should he choose to do so. Black could even meet 1.c4 with 1...e6 if he wanted to.

For the Slav, there's mostly nothing much the 1.c4 move order does. I say mostly because after 1.c4 Nf6 2.d4 c6, 3.Bf4!? is a possibility. Now if 3...d5, White has time to play 4.e3. This reaches a position where the dark-squared bishop is developed, and White is in time to prevent Black from winning a pawn with ...dxc4. However, Black can instead just meet 3.Bf4 with 3...Qb6, and the game should be equal.

Black could also meet 1.c4 with 1...c6 (intending ...d5 immediately on the next move), although here he'd have to be fine with a possible transposition into the Caro-Kann Panov after 2.e4.

See Cephalopod11's answer for more good info on this topic.
> 16 votes

# Answer
Looking at this through the intentions of the moves helps me make sense of this.

The move `1. d4` establishes a dark-square pawn in the center. Light-square control however is still missing. If possible, White will remedy this with an immediate `2. e4` but one must wait for Black's reply.

After `1. d4 d6` there's no immediate challenge and White can take the central light-squares with `2. e4`:

```
[FEN "rnbqkbnr/ppp1pppp/3p4/8/3PP3/8/PPP2PPP/RNBQKBNR w KQkq - 0 2"]

```

This controls both the light-squares and the dark-squares and Black must attack the center. If Black does not fight-back then Black will be disadvantaged and may even lose the game.

`1. ... d5` is a fine response. It takes the central light-squares but there is an interesting downside. Somehow White's dark-square control has increased too - Black's pawn on d5 can never retreat to d6 and support a dark-square break:

```
[FEN "rnbqkbnr/ppp1pppp/8/3p4/3P4/8/PPP1PPPP/RNBQKBNR w KQkq - 0 2"]

```

In fact, White has the dark-squares all wrapped up suddenly, why not challenge the light-squares with a Queen's Gambit?

```
[FEN "rnbqkbnr/ppp1pppp/8/3p4/2PP4/8/PP2PPPP/RNBQKBNR w KQkq - 0 2"]

```

So `1. ... d5` works, but `1. ... Nf6` is a different try. Note that this move also controls the light-squares in the center. It also doesn't commit the d-pawn. I am not a master but I feel like this is why `1. ... Nf6` is said to be more flexible.

```
[FEN "rnbqkb1r/pppppppp/5n2/8/3P4/8/PPP1PPPP/RNBQKBNR w KQkq - 1 2"]

```

After `1. ... Nf6` White still wants to at least make a try for the light-squares. And why not? Just like in the Queen's Gambit, we have the dark-squares wrapped up, let's get the light-squares too.

The trouble is that the Knight controls `e4` \- well, no problem, we know we can play `2. c4`:

```
[FEN "rnbqkb1r/pppppppp/5n2/8/2PP4/8/PP2PPPP/RNBQKBNR w KQkq - 0 2"]

```

Game on - and as you say, there's nothing wrong with getting to this position via the `1. c4 Nf6 2.d4` move-order. But remember our point about `1. ... Nf6` \- that it was more flexible? Well, so too are there some down-sides to `2. d4`. Notice, for example, that the dark-squares aren't under-threat. Maybe we could get that dark-square control by developing a piece:

```
[FEN "rnbqkb1r/pppppppp/5n2/8/2P5/5N2/PP1PPPPP/RNBQKB1R w KQkq - 2 2"]

```

This also reserves the right to play `d3` later, possibly supporting the `e4` square. Imagine this:

```
[FEN "r1bqkb1r/pppp1ppp/2n1pn2/8/2P1P3/3P1N2/PP3PPP/RNBQKB1R w KQkq - 0 4"]

```

Or you could go full hyper-modern:

```
[FEN "rnbqkb1r/ppp2ppp/4pn2/3p4/2P5/1P3N2/PB1PPPPP/RN1QKB1R w KQkq - 1 4"]

```

`2. d4` doesn't contribute to these plans and it's definitely not urgent, so why not try something else?
> 7 votes

# Answer
The first moves 1.d4, 1.c4. and 1.Nf3 can all potentially transpose to the same opening lines, but they can also each avoid specific openings, while also allowing others:

1.d4 gives Black the full range of both solid, well respected defenses, as well as some of the trickier, less sound responses:

* Queen's Gambit Declined, Slav Defense, Queen's Gambit Accepted
* Nimzo-Indian Defense/Queen's Indian Defense, King's Indian Defense, Grunfeld
* Benoni, Benko Gambit
* Albin Counter Gambit, Chigorin, Englund Gambit, Budapest Gambit

1.c4 allows Black to play 1...c5 and 1...e5 (entering lines that are not possible via the 1.d4 move order), but also give White some ways to avoid some of the best responses to 1.d4:

* The Mikenas Attack instead of the Nimzo-Indian
* The Anti-Grunfeld lines (where White avoids playing d4 until Black is committed to the King's Indian)
* Reti-style lines vs. the Queen's Gambit Declined and Slav setups (again, holding back d4 and playing an early e3 and/or g3)

Many 1.c4 players are either intentionally trying to avoid something like the Nimzo, or they just like the Symmetrical and King's English (1...c5 and 1...e5) and are hoping that's what the opponent will play.

Of course, some players just like to throw off their opponent, so they start with the less common 1.c4, but if they are actually happy facing all the Indian Defenses (1.d4 Nf6), usually they would just start with 1.d4.
> 5 votes

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Tags: opening, statistics, psychology, 1.d4, english-opening
---


# Question
Title: Definition: What is meant by "bishop pair" in this context?
This is a screenshot from a chess.com tutorial.

In the final sentence it says,

> White will often gain the bishop pair after 5. a3, with a sharp struggle ahead.

Obviously a3 is the pawn attacking the bishop which is pinning the knight, but I'm missing what "bishop pair" means. Assuming that bishop on b4 is one of the pair, does it mean:

* A pair of bishops, in which case which is the other bishop, and where is the gain?
* The bishop and pinned knight form a pair, which will be traded via Bc3 then bxc3, in which case, again, where is the gain? Black has destroyed the pawn structure, but not gained material. Besides, the text says that white makes the gain, not black.
* The black bishop retreats from the pawn, and somehow white makes a gain from it. In which, please help me see that sequence. Does white gain two bishops?
* Something else? Perhaps "bishop pair" is an idiom?

# Answer
"Bishop pair" is a chess term indicating you have the *pair of bishops* \- i.e. one bishop covering the light squares and one bishop covering the dark squares. If, after a3, Black plays ...Bxc3 and White responds with bxc3, then Black has lost the bishop pair because they only have one bishop left. Meanwhile, White still has both bishops, so they have the bishop pair.

The bishop pair is in general a small advantage, but it's still an advantage. In particular, you can control every square on the board with one of your two bishops. With only one bishop, there'll always be squares you can't control.

Example:

```
[FEN "rnb1k2r/1p1p1ppp/4pq2/8/8/3B4/PPP1QPPP/R1B1K2R w KQkq - 0 13"]

```

White has the Bishop pair, which is a significant advantage in this position because Black has difficulty defending the weak squares on b6, c7, d6, c5, and e5. (Plus bishops are just better than knights in open positions like this one where the center is not blocked by pawns.)

Technical note: it's unclear if two bishops on the same color still counts as the bishop pair. Certainly most of the strategy associated with having the bishop pair does not apply in this case. It's very rare to have two bishops on the same color, as well.
> 8 votes

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Tags: opening, french-defense
---


# Question
Title: What is the difference between a good player and an average player?
I have been playing chess for a while now and have played many national level tournaments as well. But I don't know if I know clearly or not what is a difference between a good player and an average player. Is it the no. of moves about which they think before playing a move or their continuous concentration which they maintain through out a complete game reducing the total number of blunders or what is it?

# Answer
There are many things that separate players of different levels, and I think you've definitely named two of the big ones: ability to calculate deeper and reducing the number of blunders. But there is more to it than just those two. Some (but not all) of the key qualities that stronger players (usually) possess are:

* More accurate calculation (not just deeper calculation).
* Recognizing the best candidate moves, which comes from the pattern recognition gained with experience, puzzle solving, and going through lots of grandmaster games.
* Better positional and strategic understanding, which allows for better planning.
* Better opening knowledge. Not just memorizing some opening lines, but actually understanding the key ideas and plans in the openings they play, and knowing how these plans extend into the middlegame and endgame.
* (This is a big one) Time management and recognizing "critical moments" in a game. You can't spend 15 mins on every move, but there are usually a few moments over the course of a game that require a deeper think. These can be a piece sacrifice that you need to make sure actually leads to mate, but they can also be a much more subtle idea like regrouping or a Petrosian-eque defensive move like Kh1 to preempt your opponent's attacking plan.
* Fighting tooth and nail for every half point. I remember noticing one of the biggest differences between US Class A players (ratings 1800-1999) and Experts (2000-2199) was how much harder it was to actually convert better positions to wins against the higher-rated players. Lower-rated players would often "keel over and die" when I had an advantage, but the stronger players would put up a lot more resistance. Take a look at games where top players lose, and pay attention to how accurate the winning side has to be. Carlsen, for example, doesn't go down without a fight and will still set traps for his opponents until the very end. Many of his draws are even games where he was worse or possibly even losing at some point, but he managed to create a narrower and narrower path to victory for his opponent until they finally made a small mistake that changed the evaluation.
> 8 votes

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Tags: rating
---


# Question
Title: How rating changes happen for tournaments starting near the end of the month?
For simplicity I will try to explain my question with a real example.

The **28th Abu Dhabi International Chess Festival - Masters** was held from **2022/08/17 - 2022/08/25** and therefore the ratings changes of that event have already been updated in FIDE
GM Erigaisi was at 2689 FIDE and gained 22 elo from that. Now his FIDE shows 2725 (also after adding the olympiad rating changes that month).

Now on **2022/08/27** the **Dubai Open 2022** started and it is still underway. GM Erigaisi is playing there too and on chess results it shows his starting rating as 2689 since the tournament started last month. Lets say he ended the event with +10 points according to chess results.

Now in the next month calculation will his rating be calculated such that **2725+10** or will that +10 be adjusted as if he played the tournament as a 2725 player thereby decreasing the amount of elo that will be added.

This won't be much at that level anyway since K factor is 10. But say a player with 2250 gained 150 rating points in Abu Dhabi and in Dubai gained another 100 points (as a 2250). Will his rating be **2250+150+100 = 2500**?

# Answer
> 5 votes
The current FIDE rating rules are set out in FIDE Rating Regulations effective from 1 January 2022. There it says:

> **7. Official FIDE Rating List**
>
> 7.1 On the first day of each month, FIDE shall prepare a list which incorporates all rated play during the rating period into the previous list. This shall be done using the rating system formula.

That is, ratings are calculated once a month for inclusion in the list. When a player's new rating for the new list is calculated the base rating used for those calculations is the player's rating on the previous list.

Regarding which games are included in the list:

> 7.1.3 The closing date for tournaments for a list is 3 days before the date of the list; tournaments ending before or on that day may be rated on the list. Official FIDE events may be rated on the list even if they end on the last day before the list date.

So, in theory games submitted for rating in the last 3 days of the month may end up being rated in the next month's list in which case they will use the player's new rating from the current month. In practice I have found FIDE to be very efficient with games submitted for rating in the last 3 days of the month usually making it into the current month.

Note that some tournaments last longer than one month. In that case:

> **4. Reporting Frequency**
>
> 4.1 For tournaments lasting more than 30 days, interim results must be reported on a monthly basis.

I once was the chief arbiter for a league tournament with one set of matches a month over a period of several months. In accordance with the regulations we submitted the games for each individual round for rating. So, in that case ratings calculated for players round 2 games did not use the same ratings as for round 1. Instead they used the ratings resulting after the round 1 calculations, etc.

---
Tags: fide, rating, elo, tournament-directors
---


# Question
Title: Confused about the central and side pawns - which are which?
We all know that the "center" comprises of the four squares that are in the very middle of the board - d4, d5, e4, e5.

Keeping this in mind, which are the central pawns, exactly, apart from the ones on the d and e files? Do they include the c, d, e and f pawns? Also, if a pawn not on a central file captures a piece and comes one file closer to the center, is that pawn a central one now, too?

# Answer
The central pawns are strictly the pawns which are on the d and e files. You can think of them as pawns which have the ability to *occupy* the central squares at some point of the game.

The c and f pawns are called the “flank pawns”. The flank pawns can also be used to try and exert an early control of the center, for example in the English Opening (for White) or the Sicilian Defense (for Black).

Yes. The flank pawns may become central pawns by capturing.

You may see this post for further reading.
> 7 votes

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Tags: terminology, pawns, center
---


# Question
Title: USCF: Should the arbiter start a time-forfeit claim?
I will be an USCF arbiter soon and I am checking the current USCF version of chess rules. Here is the link on the USCF website at 4/9/2022: USCF chess rules

In my perspective, you would have to go to page 31:

***It is very interesting that the same chess rules expresses: "Remember in FIDE competitions the arbiter can call the flag, and should do so."***

***So, USCF rules are not 100% FIDE rules.***

In my perspective, the answer is that in USCF the arbiter should NEVER start a time-forfeit claim, neither for sudden death time controls nor non-sudden death time controls, at 4/9/2022.

# Answer
> In my perspective, the answer is that in USCF the arbiter should NEVER start a time-forfeit claim, neither for sudden death time controls nor non-sudden death time controls, at 4/9/2022.

You are correct. This arises because of the bizarre USCF rules regarding flag falls not resulting in loss of the game if the opponent has not been keeping score correctly. Hence in USCF tournaments the player must "initiate a time-forfeit claim" rather than just point out the flag fall.

If the opponent has an incomplete scoresheet it can be in the interests of the *player whose flag has fallen* to call the flag fall before the opponent writes down the missing moves. For the arbiter to intervene in such a situation could be seen as benefitting one player or the other.

FIDE arbiters are required to check that players maintain a complete up to date scoresheet and penalize them if they don't.

Here are the FIDE references:

Regarding who may call flag-fall

> 6.8 A flag is considered to have fallen when the **arbiter observes the fact or when either player** has made a valid claim to that effect.

Regarding writing the moves:

> 8.1.1 In the course of play each player is required to record his own moves and those of his opponent in the correct manner, move after move, as clearly and legibly as possible

and

> 12.1 The arbiter shall see that the Laws of Chess are observed.

So, writing the moves is one of the "Laws of Chess" and ensuring that these laws are observed is the arbiter's first duty.
> 6 votes

# Answer
This is stated *explicitly* in the rules you quote. 13c1 says:

> Only the players in a game may call attention to the fall of a flag (See also 5G); it is considered to have fallen only when either player points this out. **A director must never initiate a time-forfeit claim**.

"Director" is "tournament director" which is pretty much the USCF equivalent of "arbiter".
> 2 votes

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Tags: rules, uscf, arbiters
---


title: Mental block on a tactics challenge

text:
# Question
Title: Mental block on a tactics challenge
We do a lot of tactics training with our kiddies in the chess club. This one was a real migraine maker for them, none found the solution. (I'm not 100% sure if I remember each piece correctly, but it suffices.) White to move forces mate.

```
[FEN "2k2r2/R2p4/N3p3/4Ppq1/3R4/P5p1/1PP2B2/5K2 w KQkq - 0 1"]

```

I didn't find it either, and our youth trainer had a field day since he found it with 500 Elo or so less than me. (In retrospect, it is idiotically simple.)

Please try it out first yourself. Do you run into the same block as I? The generic verdict would be "not considering a candidate move", but *why* don't you consider it? Which mental obstacle is to be overcome? (I already have a vague theory.)

# Answer
So I hope I don't make a fool out of myself, because I didn't verify whether my solution is even correct, but I want to give my 5 cents here, though this is only very anecdotal, as I consider myself neither a good nor an experienced player, but I did manage to solve this puzzle (I guess).

Rc7 jumped to my head as a candidate move right away for some reason. Probably because the puzzle was introduced as leading to mate and then I start with the most forcing move.

After this, Kd8 is forced.

The next step was trickier. Somehow I feel an inner resistance, moving the same piece twice in such small steps, so R4xd7 felt more natural. But there after following the possible responses, I realized quickly, that the Queen protects any threats from my rooks.

So how about Rcxd7? Ke8 leads to Nc7# which is good, but what about Kc8 again? This looked odd, because, what had changed since the last time the king was there? Won't I just be repeating moves if I go Rc7 again? But then it dawned on me, that there is no pawn anymore and the King can't move, so it's check mate.

So to answer the question, on my side there were two mental obstacles that I had to overcome:

1. Moving pieces multiple times in very small steps. Normally this feels wrong to me so I was hesitant here and about to disregard that move.
2. Not envisioning the board as it will look like after some captures. This missing pawn made a huge difference but there was still the initial picture of the board in my mind.
3. (Not fully appreciating the power of the knight to jump around like crazy sometimes, and then covering spots that seemed impossible, but that is a bit off here I would say)
> 3 votes

---
Tags: tactics, psychology
---


# Question
Title: USCF: Can the arbiter adjudicate a draw using the threefold repetition rule WITHOUT a player claim?
Please give me your perspective and experience about USCF sudden death and non-sudden death time controls. ***My understanding is the following:***

1. In general, the arbiter should not intervene unless a player claims a draw.
2. The player who wants to claim a draw needs to have a complete scoresheet, unless the time control is sudden death and the player who claims a draw has less than five minutes. If a player has less than 5 minutes, and it does not have a complete scoresheet, to claim a draw needs ***"the observation of a director, deputy, or impartial witness(es)"*** confirming that the threefold repetition rule has occurred.
***3) The arbiter may intervene without a player claim and declare a draw if "The same position has appeared, as in 14C, for at least five consecutive alternate moves by each player."***
3. The arbiter does not have the obligation to write players moves if any tournament player is on time pressure.
4. The player who is not claiming a draw cannot object the arbiter rule if he/she is not writing their moves.
5. The player who claims a draw should stop the clocks when he/she calls a judge about this matter.

How FIDE handle this situation? Please cite the exact rule.

I found that USCF rules are available for free at 5/9/2022 in the following link: USCF Chess Rules

It seems that this is the relevant material:

I already posted a question about this topic, but I feel that I need more information, and also that this question is specific on the arbiter duties. In addition, in this question I include non-sudden death time controls. Here is the link of the previous question: If players are not writing their moves, can they claim a draw using the threefold repetition rule in an USCF or FIDE 30+0 chess tournament?

# Answer
> 6 votes
First, in the case of draw by three fold repetition, only the players can make the claim. The arbiter may not intervene as this might advantage one of the players.

In the case of five fold repetition, the USCF rules state that the arbiter *may* declare the game drawn:

> **14K. Director declares draw for lack of progress**.
> If one or both of the following occur(s) then the TD *may* declare the game drawn:
>
> 1. The same position has appeared, as in 14C, for at least five consecutive alternate moves by each player.

This is in stark contrast with the FIDE Laws which states:

> 9.2.1 The game is drawn, upon a correct claim by a player having the move, when the same position for at least the third time (**not necessarily by a repetition of moves**)

> 9.6 If one or both of the following occur(s) then the game is drawn:
>
> 9.6.1 the same position has appeared, as in 9.2.2 at least five times.

Hence in FIDE rated chess the five fold repetition does not have to occur consecutively, it could be over a period of 20 or 30 moves, and there is no arbiter decision to be made. The game *is* drawn.

---
Tags: rules, fide, uscf, arbiters
---