title: Tournament Chess in the French Language

text:
# Question
Title: Tournament Chess in the French Language
As a continuation of my previous question (Rated Tournaments in France - For a Poor French Speaker), I have taken part in my first tournament in France.

While I can get by in the French language, I am unsure of what some common chess phrases for tournament play may be. A direct English to French translation is likely incorrect.

Could anyone enlighten me with either some phrases or a link to a resource (unable to find so far) for the below questions?

* offering a draw / claiming a draw via repetition
* calling for an adjudicator
* claiming an illegal move has been made

plus anything else that springs to mind.

The last thing I want is to offend anyone in a tournament by coming across rude or ignorant, and adhering to the etiquette of tournament play.

# Answer
> 3 votes
Native French speaker and regular tournament-goer (pre-Covid) here. The comments under the other answer are correct.

Some background tournament etiquette (probably not France-specific but necessary for what follows):

* Calling the arbiter: stop the clock, raise your hand and say "arbitre" (once, but loud enough to be heard). Do not leave your place.
* (pre-Covid, this may have changed) You shake hands with your opponent before and after the game.

Now for the French sentences:

* Offering a draw: see Evargalo's comment, "je propose (la) nulle" is IMO best; just "nulle ?" sounds quite rough to me but it is not offensive either. Refusing such as offer: "non" (no); accepting: "oui" (yes); or any other non-verbal variant (for instance, extending the hand over the board after such an offer = let's shake on it = yes).
* Claiming a draw by repetition: "nulle" (as an affirmation, not a question). Should the opponent disagree (I have never seen that happen), call the arbiter: "la même position a été répétée trois fois" (the same position has been repeated three times). "Je réclame la nulle par répétition" (I claim a draw by repetition) is correct, but formal.
* Illegal move: if you feel nice, you can point out that the move is illegal and allow the opponent to retract it ("ce coup est illégal", this move is illegal, or something more precise, for instance "on ne peut pas laisser le roi en échec", you cannot leave the king in check). The officially-correct thing to do is to call the arbiter who will apply whatever the rules say (if memory serves, in longer time controls, the opponent gets extra time for the first two offenses).
* Resigning: "j'abandonne" (I resign). Common non-verbal alternatives: tipping the king over (which some people consider mildly rude, but IMO it is not if you do it calmly and with a smile), or extending the hand over the chessboard (to shake it, implying the game is over).
* Reminding someone of the touch-move rule: "pièce touchée, pièce à jouer" (a touched piece must be played). Less useful: "pièce lâchée, pièce jouée" (a dropped piece has been played = you cannot change the square you put it on). (Only for intentional contact - if the opponent reaches for their glass across the board and accidentally touches a piece, it does not apply.)
* Adjusting pieces: "j'adoube" (must be said before touching a piece)
* Pairings: "appareillement(s)"
* Leaderboard: "classement"

Game notation is algebraic, with the following abbreviations: R=roi (king), D=dame (queen, literally "lady"), T=tour (rook, lit. "tower"), F=fou (bishop, lit. "fool"), C=cavalier (knight, lit. "rider"). For instance Alekhine's defense is written 1.e4 Cf6 instead of 1.e4 Nf6.

# Answer
> 2 votes
There is an official translation of FIDE Laws of Chess into french where you will find most phrases.

* Offering a draw: Je propose nulle.
* Calling for an adjudicator (=arbiter): Je demande l’aide d’un arbitre.
* Claiming an illegal move has been made: Je constate qu’un coup illégal a été achevé.

There has been a dictionary edited by Chess Informant with the most relevant chess phrases in English, French, German, Russian and a fifth language. But it is out of print. If you find one in an antiquarian bookshop, buy it, it might help a lot.

---
Tags: tournament
---


# Question
Title: Exchanging on d5 in queen's gambit like openings
I'm ~2170 rated but having avoided d4 d5 type setups my entire chess career, as some things are quite mysterious to me.

In positions where white has pawns on d4 and c4 and black has one on d5 (typically accompanied by some on c6 or e6, or both), I've noticed that white often exchanges with cxd5 and the reasons behind this are quite enigmatic for me. Often by doing so, white allows black's light square bishop to come out, if not immediately then, in the future. For example, some people will play 1. d4 d5 2. c4 e6 3. Nc3 Nf6 4. cxd5, or similar positions. The exchange may be featured in other positions, for example where black has played b6. Perhaps it's done in the Catalan. Some positions are obvious to me, like in the mainline of Grunfeld's where the exchange leads to a white center. However, often to me it seems that the exchange helps black in regards to piece activity. I suppose the exchange of a side pawn with a center pawn is an argument, but it seems quite soft and unsatisfying. Also, the timing of the exchange also is enigmatic. Could the exchange have happened a turn before, and why precisely now? **There are many classical queen pawn openings where this exchange is featured and I would like if someone could explain to me the typical reasons for doing this exchange.**

# Answer
Your incomprehension is very understandable. Black opens with d5 and e6 entombing the light squared bishop only for white to play cd allowing the reply ed from black and, hey presto! the bishop is free! Is white really so stupid? What's the trick?

Well, some white players want the structure that arises, the so called "Carlsbad structure" and they want to pursue the "minority attack".

Here is the pawn structure:

```
[fen "8/pp3ppp/2p5/3p4/3P4/4P3/PP3PPP/8 w - - 0 1"]

```

The basic idea is that white will advance the a and b pawns and exchange them for black's a and b pawns leaving a weak backward c pawn and a hole on c5 where white can park a piece. The long term aim is to win this weak pawn and end up in a winning ending a pawn up. QED

Of course life isn't that simple. Nevertheless the minority attack is a template which strong players (over 2000) should know. It can occur in a number of openings, not just the QGD. For instance it also occurs, with colours reversed, in the Caro Kann.

There is actually an English GM, Keith Arkell, who has this as one of his main weapons. He is an expert in the kind of endgames which can arise from this opening and the endgame is where he applies most of his effort. (He is also probably the leading expert on the KRB vs KR endgame. Although a theoretical draw he has won something like 95% of the games where he has had the extra bishop.)

He has just published a book, "Arkell's Endings", which describes his chess philosophy and gives a lot of annotated games showing his methods. The main English chess magazine just published an extract dealing with this topic and including a game. The full article is about half way through this pdf.

Here are some of Arkell's comments and the game:

> I rarely look to create unfathomable complications, I don’t carry around an armoury of opening traps, and I don’t concern myself with trying to force a win from the earliest stages. Instead, ***my opening repertoire and subsequent play are all about creating a framework*** from which I can try to acquire the tiniest of advantages, and then, inch by inch, convert that into something tangible. Unsurprisingly, I win many of my games in the ending. Very often I am not sure at what point my opponent’s position has deteriorated from what was difficult but tenable, to a forced loss.

Here is the game where Arkell demonstrates his use of the Carlsbad structure as a framework from which he extracts a win.

```
[Title "Arkell - Bradbury, EACU Open, Newmarket 2019, QGD"]
[fen ""]

1. Nf3 Nf6 2. c4 e6 3. Nc3 d5 4. cxd5 exd5 5. d4 c6 6. Bg5 Bf5 7. e3 Nbd7 8. Bd3 Bxd3 9. Qxd3 {Theory dismisses this position as about equal, or at best only very slightly better for White, but my familiarity with the arising structures gives me a good chance to gain the upper hand} 9...Be7 10. O-O h6 {Normally Black would castle here, but now, by capturing on f6, I would be able to follow up with either 12 Ne5 or 12 b4} 11. Bxf6 Nxf6 12. Ne5 O-O 13. Qf5 {This doesn’t look very ambitious, but I am playing for an endgame in which I can probe on the queenside without having to worry about counterplay} 13...Qc8 14. Qxc8 Raxc8 {My opponent doesn’t make any serious mistakes in this game, but this felt like a minor one since the action will most likely take place on the a-, b- and c-files, so the other recapture was likely preferable.} 15. Rfc1 Bd6 16. Nd3 Rfe8 17. b4 Nd7 { I had calculated 17...Ne4 18. Nxe4 dxe4 19. Nc5 b6 (or 19...Bxc5 20. Rxc5 when b4-b5 will follow, with overwhelming positional pressure) 20 Na6 with the plan of attacking Black’s c-pawn.} 18. a4 {I wasn’t sure about the consequences of 18. b5 c5 19. Nxd5 cxd4 20. exd4 Rxc1 21. Rxc1 and then something like 21...Re2. I’m a pawn up, but it all looks a bit loose, so instead I formulated a plan to fix c6 as a longterm weakness.} 18...Nb6 19. a5 Nc4 20. b5 {Threatening to undermine Black’s whole queenside with a5-a6, so more or less forcing the following sequence} 20...a6 21. bxa6 bxa6 22. Na4 Rb8 {22...Nxa5 23 Nac5 just plays into my hands.} 23. Nac5 Rb5 24. Nxa6 Ra8 25. Nac5 Raxa5 26. Rxa5 Nxa5 {And so we have arrived at base camp – the successful conclusion of the minority attack. I have one pawn island against two; Black has active pieces, so a direct assault against c6 is obviously impossible. The correct procedure therefore is to probe on the kingside in order to inflict a second weakness, or at least to gain some space over there.} 27. g4 { This is by far the best pawn move. If 27 h4 h5 it will be hard to make progress, as breaks with e3-e4 or g2-g4 will involve ruining my own pawn structure} 27...Nc4 28. Kg2 Kf8 29. h4 Ke7 30. h5 { Not only does this move fix a target on g7, but experience of playing these kinds of positions, literally hundreds of times, has taught me that there are certain mating nets Black needs to be wary of.} 30...Nb2 {I felt this was a little impatient, enabling me to activate my rook. It was better to sit tight and await events.} 31. Ra1 Nxd3 32. Ra7+ Kf6 33. Nxd3 Rb3 34. Ne1 Rb6 { Neil played this quite quickly, but I wasn’t sure whether he should be playing 34...c5 instead. Actually I had a similar game at Harrogate about four months earlier where I managed to win from the structure which would have arisen after ...c5.} 35. Nf3 Bb8 36. Rd7 Ke6 37. Rd8 {My opponent’s position has rapidly become critical. I now threaten 38. Re8+ Kf6 39. Ne5 when he will either be mated or face heavy material losses.} 37...Bd6 38. Rc8 {This was a bit lazy. As soon as I had released the rook, I regretted not playing 38. Re8+.} 38...Kf6 {There was a chance to prolong the game with 38...f5, but I could still keep up the pressure with 39 g5} 39. Nh4 { After this move, heading for f5, I could no longer see any way for Neil to avoid losing material. His c-pawn, g-pawn, bishop, and even his king have come under increasing pressure, all because his pieces were tied down to the defence of the c6-pawn – a product of White’s typical minority attack in the Carlsbad structure} 39...g6 40. hxg6 fxg6 41. Rg8 Kf7 42. Rxg6 Bf8 43. Kf3 Ra6 44. g5 hxg5 45. Rxg5 Ra2 46. Rf5+ Ke8 47. Ng6 Bd6 48. Rh5 {I have to be careful to prevent the break ...c5 at a moment when the d-pawn is safe from capture.} 48...Kd7 49. Nh4 Bb4 50. Rh7+ Ke6 51. Ng6 Rc2 { I was pleased to see this as it enables my knight to reach its ideal post, back on d3. On 51...Bd6 I intended 52 Rh6 when only an engine might be able to hang on.} 52. Nf4+ Kd6 53. Nd3 Rc4 54. Rb7 c5 55. Rb6+ Kc7 56. dxc5 Bxc5 57. Rb5 {Either Black enters a lost king and pawn endgame, or he loses the d-pawn} 1-0

```

A masterclass from an expert on the Carlsbad structure.
> 19 votes

# Answer
Some things I see:

It introduces the imbalance of half-open files: White gets the half-open c-file, while Black gains the half-open d-file. By proxy that strenghtens White's control of c5 and Black's control of e4. It sounds very abstract, but it is very relevant in lines where Black plays ...a6 (for example in the Slav Defense), because ...b6 controlling the c5 square would weaken the whole queenside. Another point is that liquidating a pair of central pawns limits dynamic possibilities in the center and it becomes very stable for both sides. That means that he pieces have less responsibilities and can be employed elsewhere.
> 2 votes

---
Tags: opening
---


# Question
Title: How did classic masters like Alekhine and Anderssen practice tactics?
How did classic masters like Alekhine and Anderssen practice tactics? Surely there was no chess.com or chesstempo at that time. How did the masters back then manage to increase their tactical awareness?

# Answer
In Joosep Grents's wonderful biography on Paul Keres, there is a brief first-hand account of tactics training in that time period. For background, Paul was a contemporary of Alekhine and almost played him for the World Champion title, but the match never materialized.

Here's what Paul Keres had to say about training tactics in the 1930s (emphasis mine):

> I used correspondence games, above all, for experimental purposes, often opting for very risky opening lines and attempting, at all cost, to create complicated positions which **I could use to train my tactical** **skills**... It is easy to notice a bias toward tactics in these games, while there are still considerable problems apparent in solving strictly technical problems.

The article notes that at one time Paul was playing more than 100 correspondence games at once.
> 10 votes

# Answer
Alekhine died in 1946. I have a copy of Fred Reinfeld's "1001 Winning Chess Sacrifices and Combinations" in 1955, 9 years after his death, which is basically a tactics training book. Reinfeld was the first dedicated chess author, as far as I know, who churned out chess books on an industrial scale. It could be that he was the first person to come up with the idea of extracting tactical motifs from games and putting a large number of them in a book and selling it.

Before Reinfeld there was the idea of games collections of short games which would contain tactical ideas, just not in such a concentrated form. I have a book called "200 Miniature Games of Chess" by J. du Mont which was published in 1941, within Alekhine's lifetime.

I suspect that players of Alekhine's generation and earlier honed their tactics by playing through short, tactical games, possibly from games collections like this.

Note that tactical motifs, like pins, discovered check, the importance and use of the 7th and 8th ranks and others, were identified and discussed by Nimzowitsch in his book "My System" published in 1929. These ideas were not new. What was new at the time was classifying and describing them as Nimzowitsch did.
> 8 votes

# Answer
Tournaments and matches. Possibly also self play/analysis.

Books were very rare and not very good back then.

Just playing more is no use unless you play better too.
> 5 votes

---
Tags: tactics, history, alekhine
---


# Question
Title: Why does ChessMaster recommend 24. Rg3 in this position?
I reached this position when playing against ChessMaster's cyber personality Laura. The engine recommends the line starting with 25. Rg3:

```
[FEN ""]
[White "Bad_Bishop"]
[Black "Laura"]
[StartPly "48"]

  1. d4             Nf6
  2. Nf3            c5
  3. d5             d6
  4. c4             Qa5+
  5. Bd2            Qa6
  6. Qc2            Bg4
  7. Nc3            Nbd7
  8. e4             Bxf3
  9. gxf3           h6
 10. h4             e6
 11. O-O-O          Ne5
 12. Be2            exd5
 13. exd5           Be7
 14. f4             Ned7
 15. Rhg1           Kf8
 16. Rg2            Ne8
 17. h5             Bf6
 18. b3             Qa3+
 19. Kb1            Bxc3
 20. Bxc3           Ndf6
 21. Rdg1           Rg8
 22. Bf3            Qa6
 23. Qe2            Qb6
 24. Re1            Qd8 25. Rg3 b5 26. cxb5 Nc7 27. Qd3 Rb8 28. Ba5 Qc8 29. a4 Qb7 *

```

To me 25. Rg3 is not intuitive and I did not consider it all in choosing a move. Granted, in the line that ChessMaster recommends, black throws away a pawn, but my question is, **what is the purpose behind 25. Rg3 and why is it the best move?**

# Answer
All of White's other pieces are placed well except the Bishop on f3. If Black moved the a8 rook back and forth then White would probably like to play Rg3, Bg2-h3, and maybe Rg3-e3. Simply put Rg3 increases the scope of the rook and the bishop.
> 12 votes

# Answer
It seems like e3 is the square that the Rook on g3 is heading for - after moving the Bishop on f3. (somewhere out of the way) This gives the g3 Rook certain access between the two f-file pawns. The idea is to allow both Rooks to work together on the e-file.
> 3 votes

# Answer
This is a very complicated position. No obvious winning plans. White has the bishop pair and much more space, but the f2,f4 and h5 pawns are all isolated, and black is very compact and defends everything. Stockfish shows +300cps advantage, but is not able to convert until maybe move 25 or so, frequently even reaches fortresses. So, I am not certain what this position is: it might be a white win(I hope so), but it might also be some kind of fortress position. In order to be certain one way or another, one needs deep analysis, which might take a couple of days.
> 1 votes

---
Tags: analysis, candidate-move
---


title: Aggressive response to 1.d4?

text:
# Question
Title: Aggressive response to 1.d4?
As black, against 1.d4, which aggressive response do I have? I looked at queen's gambit accepted, queen's gambit declined, king's Indian defence and the Slav defence. But all of this options appear to me as passive, at least passive in the opening phase. Seems to me that in all this variations white still gets a better control of the center and a more active and developed setup, whit black that has no immediate treats or tricks. I am feeling like against 1.d4 I am doomed to play a more positional and passive opening phase. Is this the case?

I am a beginner, 1500, so is quite possibile that I am missing some aggressive potential in the mentioned openings. This comes from a guy that quite enjoys playing stuff like the fried liver, Stafford gambit, Evans gambit and the Danish gambit, so I hope you can get what I am searching here.

# Answer
I have no experience of playing it, but the Albin countergambit 1. d4 d5 2. c4 e5 might be an option. It's relatively rare but doesn't seem to score too badly compared to the QGD/Slav, with significantly fewer draws than either (see stats here).
> 4 votes

---
Tags: gambits, 1.d4, queens-gambit, aggressive-play
---


# Question
Title: Black Lion opening plans for White's 5. Bc4 line
The Black Lion is a line that can be transposed from a Philidor or Pirc defense. I play with White this line.

```
[FEN ""]
1.e4 e5 2.Nf3 d6 3.d4 Nf6 4.Nc3 Nbd7 5.Bc4 Be7 6.O-O c6 7.a4 Qc7 8.Re1 h6 9.h3 g5 10.a5 Rg8 11.b4 g4 12.hxg4 Nxg4 13.Bb3 Nf8 14.a6 b5 15.d5 Bd7 16.dxc6 Bxc6 17.Nd5 Qd8 18.c4

```

As you can notice, all my play relies on opening up the queenside and occupying the d5 square. However, when Black plays 9 ...a5 shutting all my counterplay on the queenside. I really don't know what to do. Black would just maneuver his knight as usual to f8, and then something like Rg8 and g5 with a formidable kingside attack on White. I would really appreciate it if somebody can give me some lines with clear plans.

# Answer
The first thing to note is that 9. h3 is a minor mistake if your intention is to play a queenside attack. It is a diversion from your plan. It would make more sense if your plan were to attack through the center with moves like Qe2, Be3, Rd1, de, etc. In that case it would create a safe spot for the bishop on e3 by denying g4 to the black knight. All h3 is does in the plan you play is to accelerate the black kingside pawnstorm by creating a pawn lever for a later black g4.

Instead in the final position above follow Jonathan Rowson's advice and "talk to your pieces". In particular the bishop still at home on c1. Why are you attacking before you have completed your development? Particularly why are you attacking the opposite side of the board to where the enemy king is? Find a plan which involves completing your development by finding a square for the c1 bishop.

One suggestion would be to follow a plan played by Aron Nimzowitsch 100 years ago which involves fianchettoing the c1 bishop with threats of a knight sacrifice on e5 if black plays Nf8. Here are the moves up to where he has a big advantage:

```
[title "Nimzowitsch - Marco, Gothenburg 1920"]
[fen ""]

1.e4 e5 2.Nf3 d6 3.d4 Nf6 4.Nc3 Nbd7 5.Bc4 Be7 6.O-O h6 7.a4 c6 8.b3 Qc7 9. Bb2 Nf8? (9...g5! 10. Re1 Rg8 11. dxe5 dxe5) 10. dxe5 dxe5 11. Nxe5 Qxe5 12. Nd5 Qd6 (12...Qxb2 13. Nc7++) 13. Ba3 (13. e5 Qxe5 14. Re1 Ne4 15. Rxe4 Qxe4 16. Nc7++) cxd5 14. Bxd6 dxc4 15. Bxe7 Kxe7 16. e5 N6d7 17. Qd6+

```
> 5 votes

# Answer
The engine gives a very strong plan of making ...g5 as unattractive as possible by playing Nh4-f5, where in the end Black's pieces are pathetic and the Black king is still in the center. The way White can force the matters really shows how poor Black's position is.

```
[FEN ""]
1.e4 e5 2.Nf3 d6 3.d4 Nf6 4.Nc3 Nbd7 5.Bc4 Be7 6.O-O c6 7.a4 Qc7 8.Re1 h6 9.h3 a5 10. Be3 {Finishing development and enabling a more convenient recapture in case of exd4} Nf8 11. Nh4! {This move makes both ...g5 and ...Ng6 horrible concessions} g5?! 12. Nf5 Bxf5 13. exf5 {Now let us check what if Black insists that there is an attack} Rg8 14. Qe2 g4 15. g3 {Probably the cleanest demonstration of why the attack does not work} gxh3 16. Rad1 {The Black attack fizzled into nothing and White will now pressure the Black king with Rd2+Red1} (16...N8d7 17.Bxh6) (16...O-O-O 17.Bxf7) (16...h5 17.dxe5 dxe5 18.Bf4 N8d7 19.Rxd7 (19...Qxd7 20.Qxe5 Ng4 21.Qc5 {Now Nd5 is possible and wins the bishop due to the threat of cxd5 Bb5, winning the queen}) Nxd7 20.Bxf7+ Kxf7 21.Qxh5+ Kf8 22.Bh6+)

```
> 4 votes

---
Tags: opening, analysis, strategy, philidor-defense
---


# Question
Title: Why does Stockfish recommend this bishop exchange early on?
When reviewing my games on Lichess, I very often find the Lichess engine recommending to me to sacrifice the bishop early on after checking the enemy king. I have created a sample game where you can see it happening. I don't see myself in any better position there, so I am curious what I gain by doing this.

```
[FEN ""]

1. e4 c5 2. Nf3 Nc6 3. c4 Nd4 4. Nxd4 cxd4 5. d3 e5 6. Be2 Bb4+ 7. Bd2 Bxd2+ 8. Qxd2

```

I just don't understand why it wants me to move my bishop to b4 in the first place. I'd much rather want to develop my position more by doing c5 or knight f6 or similar.

# Answer
> 12 votes
I wouldn't say it was a "sacrifice", it was more like an exchange of bishops.

My lichess engine was actually giving me `...Bd6` as the first move.

> I don't understand why it wants me to move my bishop to b4 in the first place

Me neither. I doubt anyone here will have an idea. Stockfish doesn't tell us *why*. If I have to make a guess, I would say the bishop is being blocked by the d4-e5 pawn chain, so it makes sense to exchange the bad bishop off.

# Answer
> 10 votes
Once white has put pawns on the central white squares of d3, c4 and e4 his white squared bishop becomes very bad, because its mobility is drastically reduced, and his dark squared bishop becomes essential for protecting the dark squares that have become weak thanks to the pawn moves.

That means that 7.Bd2 is a blunder because it allows black to exchange the dark squared bishops leaving white with a bad position. Much better would have been 7.Nd2 followed by a3 and b4 to chase the dark squared bishop away.

# Answer
> 4 votes
Mostly when the engine suggests a such exchange maneuverer it means that either your piece has no future, or the blocking piece has a very good future. Since you need to move the bishop somewhere to get castled, it chooses to exchange it off.

If you look for plans in the variation you given, the most natural way for White to proceed is to break in the center with f4 at some point, where you can support your center with ...d6. The bishop would find it hard to find a meaningful role in this structure.

# Answer
> 4 votes
There isn't a sacrifice in the line you gave. I assume you man 6...Bb4+.

The bishop is a bad bishop because it's blocked by its own pawns in the center. 7.Bd2 is virtually forced trading black's bad bishop for white's good bishop. The alternatives for white just aren't very good.

It also frees up black's position because he can play d6 to develop the other bishop and he has Ne7 as an option too.

# Answer
> 3 votes
That is not a sacrifice at all. It is an exchange. You get rid of a bad bishop for his better one. It is positional play for a very minor advantage. But still an advantage. Enough small ones add up to be enough to win material and the game.

# Answer
> 1 votes
## Three Options

After 7.Bd2 Black has three options:

**Retreat**: Black can pull the dark bishop back. Retreating to c5 doesn't work, since White can just push the b pawn forward, and force the dark bishop to retreat again, so you'd have to go back to d6 or further. The issue with this is tempo - you've giving white a free turn to develop.

**Defend**: You can try to use your Queen or the a pawn to defend the bishop, but these are a little awkward. In the pawn's case, White can exchange for the bishop anyway, and you are left with doubled pawns on b, and now you have to defend the forward pawn or just coincide it. The Queen defense line is more complex, and I'm not sure I'm experienced enough to do it justice. Bottom line is, your Queen is either tied down defending that bishop, since you can't get any other support there easily, or White is going to exchange for the bishop (again) and either push your Queen around or try to exchange for it.

**Exchange**: Or exchange for the bishop. Your example ends with White's Queen taking the dark bishop. This doesn't really develop White's Queen, so you gain tempo by following it up with a development move - maybe the knight f6 you mention in your question.

**Bottom line**: the bishop is probably going to be exchanged, so you might as well do it in a way that doesn't give White anything. Moving the White Queen one square forward isn't much in the way of development, so that seems a good exchange.

---
Tags: opening, analysis, bishops, lichess, exchange
---


# Question
Title: How many times can the king and its surrounding squares be attacked?
In a legal position, how many times can the king and its surrounding squares be attacked? There is a total of 9 possible squares to be attacked-the square the king is on and the eight squares surrounding it. The final tally is the added total of the number of times each of the nine squares is attacked.

# Answer
> 3 votes
As @Brian Towers anticipated, here is 55 attacks.

```
[FEN "B7/1R2n3/3Q1Q2/2Q3Q1/2N1k1K1/1R4Q1/1BNQNQN1/8 w - - 0 1"]
[startply "2"]

1. Rxe7#

```

But given the loose ruleset, both sides can attack; I found 83.

```
[FEN "8/3Nnn2/1bnQqQb1/1r4Q1/1nq1k1qN/1R4Q1/1BNQqQB1/2K1Nn2 w - - 0 1"]

```

*Proof of legality:* 1. a4 b5 2. h4 g5 3. c4 d5 4. f4 e5 5. cxd5 bxa4 6. fxe5 g4 7. Rh3 gxh3 8. h5 Nf6 9. h6 Rg8 10. e6 Rg7 11. hxg7

Just for fun, here is an illegal and one-sided 88 attacks. Any piece swap will do for both colors.

```
[FEN "8/2NNNNN1/1NNQQQNN/1NQ3QN/1NQ1K1QN/1NQ3QN/1NNQQQNN/2NNNNN1 w - - 0 1"]

```

# Answer
> 2 votes
There seems to be some confusion understanding the problem, so I will post an answer, probably not the maximum, and then somebody better than me can post the best solution.

I've promoted 7 pawns to queens and one pawn to a knight.

```
[fen "R7/7b/3qnq2/2q3q1/2n1K1n1/2q3q1/3q1q3/7k w - - 0 1"]

```

Each of the 8 queens attacks 5 squares around the king = 40 Each of the 3 knight attacks 2 squares around the king = 6 The bishop attacks the king and 1 square around the king = 2

Total = 48

---
Tags: theory, problems
---


title: The Mosquito Gambit

text:
# Question
Title: The Mosquito Gambit
```
[FEN ""]
[startply "5"]

1. d4 e5 2. dxe5 Qh4 3. Nf3

```

I reached this position after following the line for the Englund Gambit. Lichess says that this is known as the Mosquito Gambit. Is it a joke opening, or does it have some hidden ideas, making it useful?

# Answer
> 7 votes
It is safe to say that it is nothing more than a joke.

First, as a reasonably strong player, I cannot see any redeeming reason to play that...no tricks, no nothing.

Second, in Mega 2020, there are only three games out of more than 8 million total, which I will give below; and looking at them, it is clear that black did not take any of them seriously. Maybe the most amazing thing about them is that one game was actually played by the famous Grandmasters Tony Miles and Robert Huebner, but that was only a 5-move draw.

Lastly, and I had never even cracked this book before, but I have the famous Stefan Bucker series in German on the Blackmar-Diemar Gambit, and the companion volume on the Englund. Bucker does not even mention 2...Qh4 in the Englund book.

```
 [Event "Interpolis-09"]
 [Site "Tilburg"]
 [Date "1985.09.13"]
 [Round "12"]
 [White "Miles, Anthony John"]
 [Black "Huebner, Robert"]
 [Result "1/2-1/2"]
 [ECO "A40"]
 [WhiteElo "2560"]
 [BlackElo "2620"]
 [PlyCount "9"]
 [EventDate "1985.08.28"]
 [EventType "tourn"]
 [EventRounds "14"]
 [EventCountry "NED"]
 [EventCategory "15"]
 [FEN ""]

 1. d4 e5 2. dxe5 Qh4 3. Nf3 Qa4 4. Nc3 Qa5 5. e4 1/2-1/2

```

Game 2 might just have been very weak children.

```
 [Event "Brasileiro U18"]
 [Site "Brazil"]
 [Date "1999.??.??"]
 [Round "?"]
 [White "Becker, Gabriel"]
 [Black "Zap, Felipe"]
 [Result "1-0"]
 [ECO "A40"]
 [PlyCount "30"]
 [EventDate "1999.??.??"]
 [EventType "tourn"]
 [EventRounds "10"]
 [EventCountry "BRA"]
 [FEN ""]

 1. d4 e5 2. dxe5 Qh4 3. Nf3 Qe4 4. Nc3 Qg6 5. Qd3 Qc6 6. e4 Bc5 7. Be3 Bb6 8. Bxb6 cxb6 9. Be2 Nh6 10. O-O Na6 11. Qd5 Qxd5 12. exd5 Ng4 13. Nd4 h6 14. Bxa6 O-O 15. Bd3 Re8 1-0

```

And the last game.

```
 [Event "LIB-ch"]
 [Site "Beirut"]
 [Date "2007.07.26"]
 [Round "2"]
 [White "Aramali, Ohannes"]
 [Black "Zahr, Hassan"]
 [Result "1-0"]
 [ECO "A40"]
 [PlyCount "39"]
 [EventDate "2007.07.25"]
 [EventType "swiss"]
 [EventRounds "9"]
 [EventCountry "LBN"]
 [FEN ""]

1. d4 e5 2. dxe5 Qh4 3. Nf3 Qb4+ 4. c3 Qb5 5. e4 Qa5 6. Bc4 Na6 7. O-O c6 8. Ng5 Nh6 9. Qf3 Qxe5 10. Nxf7 Rg8 11. Nxe5 Rh8 12. Bxh6 gxh6 13. Qf7+ Kd8 14. Rd1 Nb8 15. Na3 Bxa3 16. bxa3 Re8 17. Qf6+ Kc7 18. Qd6+ Kb6 19. Rab1+ Ka5 20. Qb4# 1-0

```

# Answer
> 4 votes
Normally you sacrifice material for the initiative or a positional compensation, but this opening clearly has nothing in it and all you are doing by bringing the queen out early is allowing white to gain a tempo on it. I would say it's like a Scandinavian a pawn down and the Scandinavian by itself is quite bad.

# Answer
> 2 votes
The Mosquito Gambit should only be played in faster blitz time controls and bullet like 3|2 or 1|0 for psychological purposes against weaker opponents. Only play it against weaker players because higher rated people know how to convert a material advantage to a winning one. It is in fact marginally better fred defense, southern variation.

---
Tags: opening, learning, beginner, gambits
---


# Question
Title: Information on adding opening knowledge to an engine
I'm writing a chess engine in C# for school purposes. As part of the assignment, I need to read something from an external document. I was thinking of reading an opening book, but I can't really find much documentation because Polyglot is used a lot of the time. I can't really use that because I don't get marks for other people's code.

Does anyone have information or a good website on how to implement a png/bin opening book in your chess engine?

# Answer
> 1 votes
there are plenty of free online files of chess openings, here are a few:

https://www.pgnmentor.com/files.html#openings http://scid.sourceforge.net/ https://www.bookup.com/ECO/chess\_openings\_ECO\_-.htm

i could only find these links as of now. I will give you more once i find more

---
Tags: opening, engines
---


# Question
Title: What will/should the arbiter do if the side which cannot theoretically lose resigns?
Assume that in an endgame, one side cannot theoretically lose (for example, his opponent has only a king) and he is not in any time crisis. In this case, what will/should an arbiter do if this player resigns? Will/should the arbiter accept the result of the resignation, or will/should the arbiter consider this as bad sportsmanship and take further actions against this player?

Though almost no reasonable player will do this under normal circumstances, I am still wondering if this had ever happened in professional games before.

# Answer
> 25 votes
The first thing to note is that the FIDE Laws of Chess are silent on this. Resignation at any time in any situation is allowed and immediately ends the game:

> 5.1.2 The game is won by the player whose opponent declares he resigns. This immediately ends the game.

Other methods of losing are qualified in some way. For example, checkmate is only valid if the preceding move was legal, a game where one player runs out of time is only a loss if there is some way (i.e. helpmate) that the opponent can deliver checkmate.

However this is not the end of the story. There are also the Anti-Cheating Regulations. They say:

> 1. These regulations deal with the investigation of suspected cheating incidents.
> 2. “Cheating” in these regulations means:
> i) the deliberate use of electronic devices (Art. 11.3.2 FIDE Laws of Chess) or other sources \> of information or advice (Art. 11.3.1 FIDE Laws of Chess) during a game; or
> ii) the **manipulation of chess competitions** such as, including but not limited to, **result manipulation**, sandbagging, **match fixing**, rating fraud, false identity, and deliberate participation in fictitious tournaments or games.

If the arbiter believes the resignation was a result of ineptitude then it should stand. There have been examples of top GMs resigning drawn positions through ignorance and ineptitude.

If the arbiter suspects some form of cheating or receives a complaint of such then this should be investigated. These things also happen.

# Answer
> 2 votes
I found a decision by the FIDE Ethics Comission (FEC) that is interesting in relation with this question. In this case (Decision 2/2020), two players were observed talking during a competition. Afterwards, one of the players wrote on her scoresheet "Draw or I win?" There were also calculations of the tournament standing and the distribution of prize-money. The arbiter forfeited both players and they were declared ineligible for prize money in the tournament. They were also banned from FIDE rated events by the FEC for 24 months (the last six months suspended and serving as probationary period). The decision arguments the following (emphasis added by me):

> 10.3. The concept of match fixing in chess may be described as an arrangement between the parties with the aim of agreeing the outcome of the game in violation of the accepted principles of sportsmanship and fair competition, **often involving deliberate underperforming by one of the parties**.
>
> 10.4. When contemplating the concept of match fixing, the EDC Chamber notes that arranged draws are widely known to occur in both national and international events. The reasons for an arranged draw may vary. For example, both of the players may want to save energy for later games, or may be satisfied with their tournament standing and are therefore averse to taking risks. There is an argument for regarding arranged draws as contrary to the concept of sportsmanship and fair competition as it takes away the competitive aspect already before the start of the game. The EDC Chamber does not however find arranged draws as unacceptable match fixing per se, primarily due to the fact that chess players are allowed under the Rules of Chess (art 9.1.2.1) to propose and agree to a draw, admittedly only during the course of the game, and **none of the parties thereby agree to lose the game**.
>
> 10.5 There are situations where arranged draws may be in violation of the concept of sportsmanship and fair competition to such an extent that it would qualify as match fixing. One example is where **one of the players is offered some kind of remuneration** to agree to a draw.

Thus, **to be considered as bad sportmanship, the decision to lose should be deliberate** (and not the result of ineptitude, as mentioned by @Brian Towers), **specially if there is some kind of remuneration or benefit for one or both players**. That would require for the arbiter to have evidence of the said remuneration or benefit or that there was an agreement between the players.

For example, in another case investigated by the Catalan Federation of Chess (Resolution 20/2019 and Appeal Resolution 5/2019, in Catalan) a higher rated player lost to a lower rated player. However, the lower rated player had already previously resigned and agreed to continue the game. By winning the game, the lower rated player ended first in his category and won a prize of 40 €. The arbiter had observed the higher rated player had had considerable advantage during the game. However, he could only act when he obtained (some days later) a WhatsApp conversation where the higher rated player said he had sold the point for 5 €. When asked by the arbiter some time later, the lower rated player recognized the facts and the arbiter denounced the facts. The lower rated player was suspended and banned from participating in Catalan Chess Federation competitions for one year and was requested to return the prize. The higher rated player did not have a Catalan Federation license and was banned from participating in Catalan Chess Federation competitions for two years.

---
Tags: rules, resigning, sportsmanship, arbiters
---


# Question
Title: What length of time should one spend looking for a combination, and what factors should one consider?
Taking time control into account, how long should one take when looking for a combination? Also, what factors should one consider when looking for a combination?

# Answer
> 10 votes
That's a very general question that I don't think you will get a solid answer for. The chance of a powerful combination being available depends largely on the pieces each side has available and developed. So the answer varies based on what stage the game is in and the positions of each side.

Instead I would focus on identifying the types of combinations you are comfortable with, and start to learn to identify boards where those combinations MAY be present, and others where the combinations is not present. If you can speed up your identification you can determine on the fly how much time to spend on evaluating each potential move.

# Answer
> 7 votes
The time spent on looking for combinations is a function of board position.

If you have few active pieces, spend minimal time looking for combinations, and more time developing strategic plans.

As more pieces come into play you will look for combinations more, particularly if there are open lines for attack. Ideally, you eventually arrive at a board position where there simply must be a combination available. At this point you search until you find it.

# Answer
> 7 votes
While good players are always alert for tactics, there are a few key "signals" that indicate that tactics and combinations might be available.

## Loose Pieces

If there are one or more enemy pieces that are hanging or under-defended, you should look for tactics that attack that piece. For example, if a bishop is defended by an enemy queen and attacked by a friendly rook then the bishop is under-defended.

## Weak King

If the enemy king does not have many friendly pieces around it, then it might be possible to stir up an attack. If the king is castled, look for ways to disturb the pawn shield in front of the king, or look to see if the h7 square can be attacked. For example, a Greek gift sacrifice might be possible.

If the king has *not* castled, then be alert for tactics based on the f7 square. f7 is frequently weak because only the king defends this pawn.

## Lead in Development

If you have a moderate lead in development (an extra piece or two developed), then it is frequently possible to do something useful with the extra forces. Most usually this is an attack on the enemy king, but it could be something as simple as gaining a space advantage too.

## Enemy Piece Low on Squares

If an enemy piece doesn't have many squares to which it can safely move, it might be possible to trap the piece. This most often happens with the enemy queen, but it is possible to trap rooks, knights, and bishops as well. Here's an example from one of my own games:
Solution:

> 1...Re1+ 2.Kg2 Be3! -+

# Moves to Consider

If you have decided to look for tactics, you should consider all of the checks available as well as all of the captures. This may sound slightly radical, but almost all tactics will fall into one of these two categories. Moves that place a piece close to the enemy king should also be studied. Almost all chess tactics are based on double attacks (or double "threats"), so look for moves that unmask an attack (discovered attack) or that fork two pieces.

# Amount of Time to Spend

Depending on how much time you have left, you should spend as much time as you need to look at all of the possibilities. If you have only 5 minutes left, then it might be prudent to just look at obvious moves fairly quickly, but if you have more than an hour left on the clock, there is no excuse for missing a winning tactic.
With practice you will be able to look at all of the captures and whittle them down to one to three worth considering very quickly. For example, sacrificing a queen for a bishop should at least be checked out (it's a capture), but almost all the time it is sufficient to look just another move further and decide that there is no follow up. The best players spend over an hour on a single move if it is possible that there is a winning attack in the cards. The biggest reason for this is that they are able to win with just a few minutes left on the clock, so it is worth the initial time investment in order to gain a winning position.

To conclude, here's another example from one of my own games. I was black, and I got to this position. Notice that I am up a piece, but black now has a knockout blow to end the game immediately. I spent some time looking for tactics because the enemy king is weak and the king is also low on squares (only can play `Kxg2`). Since it is likely that a successful tactic will win the game, I was willing to spend about half of my remaining time on the move (although I spent significantly less than that in the game). I had about 35 minutes left.

> 1...Bxg3! 2.hxg3 Qh5 0-1

# Answer
> 1 votes
I am trying to give an answer from a practical point of view.
(Disclaimer: the answer is essentially opinion based).

Let us look at the thought process when one plays chess. Suppose it is your turn to move. What you look for depends a lot on the position at hand (and your playing style). You would notice the tactical and/or positional resources first (your resources and your opponent's resources). Unless you have a clear target, you should rely on judgement and intuition and play a move that improves your position and/or helps achieve your overall game plan (or stop your opponent's). If you have a clear target (eg: I have multiple ways to threaten checkmate), then start calculating.

You should start looking for a combination only when you have **multiple resources at hand** (similar to two weakness principle of Steinitz). The following are some of the resources:

* sufficient lead in material (eg: at least a lead of a minor piece)
* better piece activity and/or coordination
* (almost) trapped opponent pieces (higher their value, the better; the king is the best)
* opponent king is vulnerable (eg: your pieces eye the squares around opponent's king, (ii) opponent king is (almost) out in the open)
* you have a sequence of forcing moves
* you have protected passed pawns about to promote

So, how much time you should spend on looking for a possibility of a combination? Depends on how many resources you have and how good those resources are. I would recommend spending more time on spotting your resources than the calculation. Even when a combination exists, it may be hard to spot if you start calculating from the position. Sometimes, you have to think about what pattern/theme you want to achieve, and then look for ways to make it possible.

By the way, you should look for ways to cash out your advantages if all your advantages are temporary (for details, see the end of this page).
Kudos.

---
Tags: tactics, combinations
---


# Question
Title: Is calculation the most important aspect of playing chess?
In many of my games, I've come across opponents who can calculate really well and deeply. Generally I feel that I lose if I can't calculate as well as my opponents. So my question was really if calculation was the most important aspect of playing chess. Would the person who calculates better normally win?

# Answer
> Would the person who calculates better normally win?

If everything else is equal then the answer is obviously "Yes".

However, everything else is rarely equal. Fixating on calculation is very common in chess players. Here is another question about calculation which clearly demonstrates this fixation. The fixation is so clear that the best answer easily pinpoints this in the first two paragraphs. BlindKungFooMaster then goes on to make the key point which is -

> In my experience ratings first and foremost reflect positional understanding. Calculation skills make a much smaller difference, at least above a certain threshold.

This fixation with calculation is, when considered rationally, obviously wrong. The strongest chess is not pure computer chess, chess based on pure calculation, it is correspondence chess where a human being moderates pure calculation with their positional understanding.

This was certainly the case before AlphaZero. AlphaZero's recent success is down to an attempt to incorporate positional understanding into computer chess which has worked better than more simplistic ideas like adjusting scores according to ideas like doubled pawns, central knights versus dim knights on the rim, king safety in the middlegame, centralised king in the endgame, etc. It would be very interesting to see correspondence players being able to use AlphaZero-like computers in their competitions.
> 7 votes

# Answer
Indeed. Accurate calculation is the source of all success in chess. Strategic ideas will only work if tactics support them. While other aspects of the game are also helpful and can make the difference, nothing can close the gap if there's a big difference in calculation.
> 3 votes

# Answer
evaluation is the most important aspect of chess. The ability to judge if the position is good or bad without needing for deep calculation is vital. There are limits to how fast humans can calculate and in the end, you need to know if the line you calculate is good or bad. Though admittedly, the terms are somewhat vague. Does a grandmaster beat 50 people in a simul because he calculates better than his opponents. In some way you could say yes, when he calculates he is able to pick out the most important lines. Of course he also wins because he doesn't need to calculate as much because of his positional understanding, his ability to evaluate positions without spending much time or effort on it. So depending on what you mean by calculation ability, you may come to different conclusions. As an aside, stockfish examines 100 million positions a second. Alpha zero examines 100,000 positions a second. How many positions do humans examine a second?0 to 10. No doubt if computers were limited to this computational limitation, stockfish and alpha zero would be crushed by professionals, probably even amateurs.
> 2 votes

# Answer
**YES!** Calculation is the most important skill in chess.

Why do you think computers are stronger at chess than humans? It is not their positional understanding or long-term planning; It is pure brute force calculation.

When I was rated 2080 I prepared for a tournament just by studying puzzles. I studied for hours a day and my head hurt from it. I took a couple days off before the tournament so I could be rested. Then I had a performance rating of 2500! I didn't get any opening advantages, in fact some I was slightly worse positionally; but I managed to get complicated positions and found nice tactics.
> 2 votes

---
Tags: opening, learning, calculation
---


# Question
Title: How does Stockfish know if the king is in check?
I am writing a chess engine. I need to know how to tell if the king is in check. I was thinking that maybe I can use the approach that Stockfish uses. Where and how in Stockfish's code is check detected?

# Answer
> 25 votes
If you're curious about the Stockfish code, it can be found here:

```
 si->checkersBB = attackers_to(square<KING>(sideToMove)) & pieces(~sideToMove);

```
1. We call the `attackers_to` method to figure out if any pieces are attacking the king's position, including pieces on the king's side.

```
 Bitboard Position::attackers_to(Square s, Bitboard occupied) const {

    return  (pawn_attacks_bb(BLACK, s)       & pieces(WHITE, PAWN))
         | (pawn_attacks_bb(WHITE, s)       & pieces(BLACK, PAWN))
         | (attacks_bb<KNIGHT>(s)           & pieces(KNIGHT))
         | (attacks_bb<  ROOK>(s, occupied) & pieces(  ROOK, QUEEN))
         | (attacks_bb<BISHOP>(s, occupied) & pieces(BISHOP, QUEEN))
         | (attacks_bb<KING>(s)             & pieces(KING));
 }

```
2. We then call the `pieces` function, which returns all the pieces owned by the opposite side
3. Finally, we run an AND operator to confirm if any of the opposite side's pieces are threatening the king.

The code is very well written and relatively straightforward to follow, in case you'd like to explore it further.

# Answer
> 18 votes
> Where and how in Stockfish's code is check detected?

This is simple engine programming. You will need to build a bitboard of the attacking squares and two bitboards of your king, one for each color. You will then run AND on the two bitboards. If the result is non-zero, you know the king is in check.

I can show you the code in Stockfish, but does my answer make sense to you? If not, please add a comment so I will try to grab some code.

# Answer
> 15 votes
Your question has nothing to do with Stockfish. Though it may be interesting to check the original source code.

This is purely algorithmic.

One dumb solution would be implementing a boolean function (is\_check) that takes an array as input representing the board. Only white pieces can check the black king, except the white king and vice versa.

If one of the following conditions is verified then there is a check on the board(return True) :

* If a knight is placed at (-+)2(-+)1 or (-+)1(-+)2 squares from your king
* If a pawn is placed at (-+)1+1 squares from your king (depends on the side you make the verification for as pawns move and attack only in one way)
* If your king is in diagonal of a bishop or a queen and that no other pieces interferes
* If your king is aligned (column/row) with a rook or a queen and that no other pieces interferes

Otherwise return False.

Note that such a function could be used in another method to check if a planned move is legal (if your king is in check after you played, your move is illegal)

---
Tags: engines, stockfish, programming
---


# Question
Title: How do you know when a FEN position is legal?
I am making a research on validating FEN positions, at first it is obvious the basics things to look for, such as checking if there are only two kings and making sure the rows or columns add up and those kinds of things. But what other checks should I do to completely make sure a FEN is legal?.

# Answer
Here is a well organized list that should validate 99.99%+ of common positions:

**Board:**

* There are exactly 8 ranks (rows).
* The sum of the empty squares and pieces add to 8 for each rank (row).
* There are no consecutive numbers for empty squares.

**Kings:**

* See if there is exactly one w\_king and one b\_king.
* Make sure kings are separated and are *at least* 1 square apart.

**Checks:**

* Non-active color is *not* in check.
* Active color is checked less than 3 times (triple check is impossible); in case of 2 that it is never pawn+(pawn, bishop, knight), bishop+bishop, knight+knight.

**Pawns:**

* There are no more than 8 pawns from each color.
* There aren't any pawns in first or last rank (row) since they're either in a wrong start position or they should have promoted.
* In the case of en passant square; see if it was legally created (e.g it must be on the `x3` or `x6` rank, there must be a pawn (from the correct color) in front of it, and the en passant square and the one behind it are empty).
* Prevent having more promoted pieces than missing pawns (e.g `extra_pieces = Math.max(0, num_queens-1) + Math.max(0, num_rooks-2) + Math.max(0, num_knights-2) + Math.max(0, num_bishops-2)` and then `extra_pieces <= (8-num_pawns)`). A bit more processing-intensive is to count the light-squared bishops and dark-squared bishops separately, then do `Math.max(0, num_lightsquared_bishops-1)` and `Math.max(0, num_darksquared_bishops-1)`. Another thing worth mentioning is that, whenever the `extra_pieces` is not 0, the other side must have less than 16 pieces because for a pawn to promote it needs to walk past another pawn in front and that can only happen if the pawn goes missing (taken or playing with a handicap) or the pawn shifts its file (column), in both cases decreasing the total of 16 pieces for the other side.
* The pawn formation is possible to reach (e.g in case of multiple pawns in a single col, there must be enough enemy pieces missing to make that formation), here are some useful rules:

1. it is impossible to have more than 6 pawns in a single file (column) (because pawns can't exist in the first and last ranks).
2. the minimum number of enemy missing pieces to reach a multiple pawn in a single col `B to G 2=1, 3=2, 4=4, 5=6, 6=9 ___ A and H 2=1, 3=3, 4=6, 5=10, 6=15`, for example, if you see 5 pawns in A or H, the other player must be missing at least 10 pieces from his 15 *captureable* pieces.
3. if there are white pawns in a2 and a3, there can't legally be one in b2, and this idea can be further expanded to cover more possibilities.

**Castling:**

* If the king or rooks are not in their starting position; the castling ability for that side is lost (in the case of king, both are lost).

**Bishops:**

* Look for bishops in the first and last ranks (rows) trapped by pawns that haven't moved, for example:

1. a bishop (any color) trapped *behind* 3 pawns.
2. a bishop trapped *behind* 2 **non-enemy** pawns (not by enemy pawns because we can reach that position by underpromoting pawns, however if we check the number of pawns and `extra_pieces` we could determine if this case is possible or not).

**Non-jumpers:**

* (Avoid this if you want to validate Fisher's Chess960) If there are *non-jumpers* enemy pieces in between the king and rook and there are still some pawns without moving; check if these enemy pieces could have legally gotten in there. Also, ask yourself: was the king or rook needed to move to generate that position? (if yes, we need to make sure the castling abilities reflect this).
* If all 8 pawns are still in the starting position, all the non-jumpers must not have left their initial rank (also non-jumpers enemy pieces can't possibly have entered legally), there are other similar ideas, like if the white h-pawn moved once, the rooks should still be trapped inside the pawn formation, etc.

**Half/Full move Clocks:**

* In case of an en passant square, the half move clock *must* equal to `0`.
* `HalfMoves <= ((FullMoves-1)*2)+(if BlackToMove 1 else 0)`, the +1 or +0 depends on the side to move.
* The HalfMoves must be `x >= 0` and the FullMoves `x >= 1`.
* If the HalfMove clock indicates that some reversible moves were played and you can't find any combination of reversible moves that could have produced this amount of Halfmoves (taking castling rights into account, forced moves, etc), example: a side with many pawns and a king with castling rights and a rook (the HalfMove clock should not have been able to increase for this side).

**Other:**

* Make sure the FEN contains all the parts that are needed (e.g active color, castling ability, en passant square, etc).

---

**Note:** there is no need to make the *'players should not have more than 16 pieces'* check because the points *'no more than 8 pawns'* \+ *'prevent extra promoted pieces'* \+ the *'exactly one king'* should already cover this point.

**Note2:** these rules are intended to validate positions arising from the starting position of normal chess, some of the rules will invalidate some positions from *Chess960* (exception if started from arrangement Nº518) and generated puzzles so avoid them to get a functional validator.
> 26 votes

# Answer
```
\s*([rnbqkpRNBQKP1-8]+\/){7}([rnbqkpRNBQKP1-8]+)\s[bw-]\s(([a-hkqA-HKQ]{1,4})|(-))\s(([a-h][36])|(-))\s\d+\s\d+\s*

```

Here's a regular expression that I use to ensure that a FEN string is actually valid. It doesn't do any testing for a legal/illegal position, but it's a good starting point.
> 12 votes

# Answer
For the others, there is a simple function in Stockfish engine, that validates a FEN String.

```
bool Position::is_valid_fen(const std::string &fen) {
   std::istringstream iss(fen);
   std::string board, side, castleRights, ep;

   if (!iss) return false;

   iss >> board;

   if (!iss) return false;

   iss >> side;

   if (!iss) {
      castleRights = "-";
      ep = "-";
   } else {
      iss >> castleRights;
      if (iss)
         iss >> ep;
      else
         ep = "-";
   }

   // Let's check that all components of the supposed FEN are OK.
   if (side != "w" && side != "b") return false;
   if (castleRights != "-" && castleRights != "K" && castleRights != "Kk"
       && castleRights != "Kkq" && castleRights != "Kq" && castleRights !="KQ"
       && castleRights != "KQk" && castleRights != "KQq" && castleRights != "KQkq"
       && castleRights != "k" && castleRights != "q" && castleRights != "kq"
       && castleRights != "Q" && castleRights != "Qk" && castleRights != "Qq"
       && castleRights != "Qkq")
      return false;
   if (ep != "-") {
      if (ep.length() != 2) return false;
      if (!(ep[0] >= 'a' && ep[0] <= 'h')) return false;
      if (!((side == "w" && ep[1] == '6') || (side == "b" && ep[1] == '3')))
         return false;
   }

   // The tricky part: The board.
   // Seven slashes?
   if (std::count(board.begin(), board.end(), '/') != 7) return false;
   // Only legal characters?
   for (int i = 0; i < board.length(); i++)
      if (!(board[i] == '/' || (board[i] >= '1' && board[i] <= '8')
            || piece_type_is_ok(piece_type_from_char(board[i]))))
         return false;
   // Exactly one king per side?
   if (std::count(board.begin(), board.end(), 'K') != 1) return false;
   if (std::count(board.begin(), board.end(), 'k') != 1) return false;
   // Other piece counts reasonable?
   size_t wp = std::count(board.begin(), board.end(), 'P'),
      bp = std::count(board.begin(), board.end(), 'p'),
      wn = std::count(board.begin(), board.end(), 'N'),
      bn = std::count(board.begin(), board.end(), 'n'),
      wb = std::count(board.begin(), board.end(), 'B'),
      bb = std::count(board.begin(), board.end(), 'b'),
      wr = std::count(board.begin(), board.end(), 'R'),
      br = std::count(board.begin(), board.end(), 'r'),
      wq = std::count(board.begin(), board.end(), 'Q'),
      bq = std::count(board.begin(), board.end(), 'q');
   if (wp > 8 || bp > 8 || wn > 10 || bn > 10 || wb > 10 || bb > 10
       || wr > 10 || br > 10 || wq > 9 || bq > 10
       || wp + wn + wb + wr + wq > 15 || bp + bn + bb + br + bq > 15)
      return false;

   // OK, looks close enough to a legal position. Let's try to parse
   // the FEN and see!
   Position p;
   p.from_fen(board + " " + side + " " + castleRights + " " + ep);
   return p.is_ok(true);
}

```
> 5 votes

# Answer
There is nothing in the FEN specification saying that the represented position must be reachable from the initial array. Proving that a given position is reachable from the initial array is an unsolved problem.

In a valid FEN string, the half move count must be in agreement with the en passant target square; if a target square is present, then the half move count must be zero. the half move count must also be in agreement with the full move number; e.g., a half move count of ten is incompatible with a full move number of three.
> 4 votes

# Answer
Coming to the party late.

Firstly I do not think it’s possible to validate 100% that a position is legal as the questioners asks. There are tens of thousands of retroanalytic problems which dance creatively on the border of legality and some of the reasons why a position is illegal are extremely subtle. I believe that the problem of legality is likely to be NP-complete (as the board size scales) although I haven’t seen any published results along those lines. Certainly features such as impostors, retro-shielding, tempo (both in races and in parity), blocking, castling right disruption, en passant and Ceriani-Frolkin promotions (including exotica such as Schnoebelen) as well as such recondite matters as dead position rule are not going to yield to simple rules.

So given that this broad program is likely unachievable, how far should one go in checking candidate positions?

If it’s for a conventional program to support orthodox over the board play then it might be appropriate to have checks as suggested in the top answers to pick up some typos like board size not right - that’s a common one if the engine does not support altered board sizes.

A programmer may enjoy specifying further legality checks but I’ve found from using many diagramming tools that less is more from a UX perspective.

I may want to show a mating matrix for example, which would only be a partial position. It’s distracting to insist that the uninvolved king be shown.

Or I may want to show a range of endgame positions in which one side has a definite win. This may involve having numerous bKs.

Even knowing that one is just focusing on forward play analysis for non-fairy chess only, I think validation should be modest.

It’s not possible to 100% validate whether a position is legal, but why should validation matter? We can play chess whether or not the position happens to derive from the starting position (so-called “game array”). There might be a very interesting position to analyse but it just happens that it’s illegal.

For example there’s a welll-known class of endgame zugzwang positions with wBa1 wPb2. Even tablebases include these kinds of positions because it’s more trouble to exclude them than include them, and losing them throws away interesting new information.

Or if I’m in the middle of constructing a problem, I might have e.g. 19 black pieces. That’s fine - I can try to reduce them later. Some published compositions have illegal diagrams. The idea may simply not be achievable with a sound diagram. According to the chess problem conventions (the Codex) legality is not required for soundness.

Finally - I’ve corrected hundreds of diagram errors in working with a database over the years, but only a tiny fraction resulted in illegality. Typically, it’s a piece on an adjacent square: still completely legal. If programmer effort is spent to help avoid transcription errors, e.g. by enabling easy import/export of different formats, including images, that would be more valuable.

The point I’m making is that rarely do I think “oh I’m glad the program is checking legality” but often I think “why did the programmer feel they need to check legality? It stops me from doing what I need to do here.”

I can’t imagine my perspective being popular in this thread but it’s a sincere answer.

So beyond checking for SQL injection etc, at most I would check just that forward moves can work in the engine which is going to be consulted, e.g.:

* Is there at most 1 king on each side?
* Are there no pawns on the first or eighth rank?
* Is the side to move not giving check already?

This is sensible defensive programming and there’s no reason to go further.

If that’s three YESes then we can play chess forwards from this diagram which is much more important than legality. And even this short list of conditions one might need to loosen sometimes (rex multiplex, dummy pawns, lese majeste).
> 4 votes

# Answer
Here is a simple backtracking algorithm, provided that you have a function that can check reverse legal moves at every board state (also known as position):

```
function is_legal_state(state,move)

   //Terminate if a starting state was found. This immediately implies there
   //was a legal game that generated this state, in fact the backtracking
   //can tell you precisely such a game
   if (state in starting board state)
     return true

   //Apply some move to get to a new state, state is a persistent object
   apply_reverse_move(state,move)

   //Generate all legal "reverse" moves, that is, moves that could have
   //been performed to get to the current state from another position,
   //provided the previous position was valid. You do not have to check the
   //validness of the previous state, you just have to make sure the
   //transitioning move was valid
   legalmoves = enumerate_all_reverse_moves( state )

   for local_move in legalmoves:
     return is_legal_state(state,local_move)

   //Reverse the move that was previously applied so backtracking can
   //work properly
   reverse_reverse_move(state,move)

   return false

```
> 3 votes

# Answer
Also , if the K is checked twice , the position must have resulted from a discovered check - Q and R,B or N , N and R or B , or R & B. Pawns are never involved in a discovered check.
> 0 votes

---
Tags: fen, illegal-move
---


# Question
Title: Is Bg4+ good in this position in the Alekhine Defense?
This is one of my games

```
[FEN ""]
1.e4 Nf6 2.e5 Nd5 3.d4 d6 4.Bc4 Nb6 5.Bb3 Nc6 6.Bf4 dxe5 7.dxe5 Qxd1+ 8.Kxd1, Bg4+ 9.f3 Bh5 10.g4 Bg6

```

Black to move, I played `dxe5, dxe5, Qxd1 Kxd1` and now I played `Bg4+` so that he plays `f3` and block his knight, well if he blocks the check with his knight i take it.

flip the board to see from my point of view, i don't know how to flip it by default.

and after `f3` I played `Bh5` so that he plays `g4` stretching his pawns and then `Bg6`

Is this setup good for black? Is there a better setup?

I rarely play this defense and there isn't too much material on balogh variation, so i was trying to avoid some common traps if I fianchetto the black bishop so I tried to block the knight.

I'm not asking to analyze this particular game because my opponent is below 2000 so if you play correctly you could beat him, I'm asking is `Bg4+` playable at the GM or masters level? If not, why not?

# Answer
```
[FEN ""]
1. e4 Nf6 2. e5 Nd5 3. d4 d6 4. Bc4 Nb6 5. Bb3 Nc6 6. Bf4 dxe5 7. dxe5 Qxd1+ 8. Kxd1, Bg4+ 9. f3 Bh5 10. g4 Bg6

```

I think that the position after `10...Bg6` is better for black. The white bishops are not collaborating very well. In fact, the white bishops are virtually useless at the moment. In addition, the white king needs to make a couple of moves to find a reasonable position, if it will find it at all.

Black wants to play `O-O-O`, `e7-e6` and `h7-h5`. White could very well become crushed here. I think that `6.Bf4` was not the best choice for white, `6.e6` or `6.exd6` should be better.
> 3 votes

# Answer
I do not see it at GM level nor IM level.

At ALL games chesstempo shows a winning % of 75 for black, and 100% for g4.

At your level it is definitely playable.

As an aside you would not see me play that variation as white. The two pawn attack seems to be far better than this variation.
> 1 votes

---
Tags: opening, analysis, alekhines-defense
---


# Question
Title: Why is the 'classical' Nimzo-Indian called the Noa variation?
I recently played 1. d4 Nf6 2. c4 e6 3. Nc3 Bb4 4. Qc2 d5, and it was coded as the **Noa** variation of the Nimzo-Indian. There was a Josef Noa of Hungary, who lived from, 1856-1903, but his recorded games do not include a Nimzo-Indian, let alone this variation. Why is it named after him then?

# Answer
> 7 votes
The Oxford Companion to Chess says that the Noa Variation of the Nimzo-Indian was played regularly by Josef Noa, but that he reached the position after 1.d4 d5 2.c4 e6 3.Nc3 Bb4 4.Qc2 Nf6.

# Answer
> 0 votes
It's probably because he has notable games playing with it or he had analysis published on it.

---
Tags: opening, terminology, nimzo-indian
---


# Question
Title: Are there any resources where one can view the popularity of a move by year?
I am currently under the impression that White players are allowing the Nimzo-Indian more and more, whereas before they were dodging it via 3. Nf3.

I wanted to check if that is true, but usually databases do not contain this information explicitly. Are there any resources (software or websites) that have this feature?

# Answer
SCID's Opening Report shows some statistics which may be useful here. From a given position, one of the things it does is generate a table which shows what moves are common from a given position:

```
4.2 Moves from the report position
    Move   ECO       Frequency    Score  AvElo Perf AvYear %Draws
 1: Nf3    E10a     8561: 50.8%   56.1%  2622  2665  2009   56%
 2: Nc3    E00d     6495: 38.5%   55.6%  2607  2654  2008   54%

```

The "AvYear" column there shows the average year in which the move was played.

And another table looks like this:

```
1.4 Current popularity

Year               1800-99 1900-49 1950-69 1970-79 1980-89 1990-99 2000-09
Once every X games   ---     24      19      13       6      33      12

Frequency in all years:   once every 12 games
In the 10 years to today: once every 13 games (down 7% from all years)
In the  5 years to today: once every 12 games (no change from all years)
In the  1 year  to today: once every 0 games (no change from all years)

```

which seems like it would be useful.
> 4 votes

---
Tags: software, database, websites
---


title: An interesting endgame

text:
# Question
Title: An interesting endgame
The following position has only eight pieces on the board with Black to move, but it is very tricky. I started trials with my modest means (Houdini 6.02) and White won 3/3 times, but after very complicated lines. I went deep in one case at d= 31/126. Is the ending really won for White?

```
[FEN "1r6/8/1P1Q2k1/K2P4/N7/3q4/8/8 b - - 0 0"]

```

# Answer
> 4 votes
Did Houdini use the 6-man databases? How did the first few moves go?

If Houdini could find nothing better for White than taking the Rook then it's a draw (given that White's pawns are moving down as stated in the comments). Wherever Black moves the King, the continuation Qxb8 Qxd5+ yields a database draw (presumably by perpetual check), and the same is true if White first checks on c7 or e5 and plays Qxb8 after Black returns to the sixth rank or goes to h4/g4.

---
Tags: analysis, endgame
---


# Question
Title: Which chess website has the strongest players?
The debate on which is the "best" chess website tends to be subjective and thus is inconclusive. On the other hand, the site that has the strongest players should be objectively ascertainable provided metrics are available.

So which is the strongest chess website in terms of:

* Number of registered titled players (FM, WFM, IM, WIM, GM, WGM)
* Number of active (routinely visit) titled players
* Number of super-GMs (\> 2800)
* Or other verifiable metrics.

# Answer
ICC and playchess.com are definitely the top two in terms of the number of registered titled players who play actively.

I was able to find metrics on how many titled players are on ICC, seen here; I couldn't find the numbers for playchess, however they are similar. Many titled players play on both.
> 11 votes

# Answer
As of 2020 I believe by far the most popular sites to play online chess are lichess, chess.com and chess24.

I am not aware of any publicly available statistics on the metrics you suggest. From what I see many of the top players are active on several sites.

The commercial websites chess24 and chess.com are likely paying some of the titled players giving them an advantage. Still, even Magnus Carlsen is seen regularly on lichess as well.

On the other hand, what should count most would be, how likely is it that you play a game against a titled player. If that is your aim, the total number of titled players is fairly irrelevant and you'd better look at what tournaments/shows/... the websites offer in this respect.

Banter blitz sessions are one way, but there are also tournaments (particularly those with minimum rating requirements) that are a good way to find titled players.
> 8 votes

# Answer
chess.com is definitely one of the contenders. If you're a member, you'd know that GM Carlsen, GM Caruana, GM Nakamura; to name a few, are quite active there.
> 5 votes

# Answer
The question was which site has the strongest players. I presume this means rating to strength ratio. ICC is the leader there in my opinion, you really have to know your chess to get a good rating; it's a proper 'club'.
> 0 votes

---
Tags: online-chess, grandmaster
---


# Question
Title: King + Queen vs. King + Queen - is this a draw?
Black and white both have one queen and the king. Is this game a draw?

# Answer
The side to move first in KQ vs KQ wins in 41.75% of the positions. That's because the side to move first gets the first check, which is often decisive in these major-piece endgames - compare how many KQQ vs KQQ positions, which ostensibly have equal material, are won by the side to move first (83%).

Caveat: "positions" here refers to all legal positions, some of which might not be realistic in practical play.
> 4 votes

# Answer
There are various positions that matter for pawn endgames. Often both sides promote to queen and then the side that moves first still wins.

This can happen *right after promotion, when the king of the stronger side is close by.*

Some examples:

```
[FEN "8/1KP1q3/8/8/3k4/8/8/8 w - - 0 1"]

1.Kb8?? {Ka8 is correct} Kc5! 2.c8=Q+ Kb6 {And white can't prevent checkmate}

```

and

```
[FEN "8/6p1/8/8/7k/5K2/2P5/8 w - - 0 1"]

1.Ke4! g5 2.c4 g4 3.c5 g3 4.Kf3 Kh3 5.c6 g2 6.c7 g1=Q 7.c8=Q+ {Check!} Kh4 {Otherwise Qh8#} 8.Qh8+ Kg5 9.Qg8+ {Wins the queen}

```

and

```
[FEN "8/8/8/p7/k7/3K4/3P4/8 w - - 0 1"]

1.Kc4! {Locking up the black king so it has to spend an extra tempo} Ka3 2.d4 Kb2 3.d5 a4 4.d6 a3 5.d7 a2 6.d8=Q a1=Q 7.Qd2+! Kb1 (7...Ka3 8.Qb4+ Ka2 Qb3#) 8.Kb3 {White wins. }

```

Source: *100 Endgames You Must Know*, by Jesus de la Villa.
> 3 votes

# Answer
Unless there is some forced sequence that leads to mate or either side losing the queen, King+Queen vs King+Queen will be an easy draw with correct play.
> 2 votes

---
Tags: endgame, draw, queens, kings
---


# Question
Title: How long can a player hold off a draw by the 50-move rule?
Going by rules strictly about the board state, how long can a player theoretically hold off a draw by the 50-move rule? White will play as long as possible, and not want to lose. Black will claim a draw as soon as possible, if not win, so threefold repetition and dead position apply.

Here is my starting offer of **703 moves**

```
[FEN "5bkq/p1p1p1pR/P1P1P1P1/8/4K3/8/P1P1P2P/7n w - - 0 1"]

1. Rxh8+ Kxh8 2. Kf3 Nf2 3. Kxf2

```

After taking 1 move to capture the queen and 2 for the Black knight, White starts the 50-move reset counter. White shuffles around their king to avoid repetition while Black's king is entombed. Every 50 moves thereafter, White plays a pawn move, with 12 total (playing h6 loses). After the 12th one, it will be another 50 moves until Black may rest: 1+2+50+(12\*50)+50=704. (White's h-pawn position prevents dead position.)

# Answer
I interpret the following

> White will play as long as possible, and not want to lose. Black will claim a draw as soon as possible, if not win

as meaning that **Black does not help** (i.e., Black tries to either win or draw as fast as possible, while White tries to make the game as long as possible and then draw or win). I suggest the following position with **1865 moves**.

```
[FEN "7k/8/4N3/6N1/8/8/PPPPPPPP/4K3 w - - 0 1"]

```

It seems to me that White can do 6 moves with each of the 4 left-side pawns (each one promotes to a bishop on its last move), then (3, 4, 2, 4) moves with the remaining four pawns. Before the first pawn move, White can play 13 waiting moves with the king while avoiding threefold repetition. Between each subsequent pawn move, White can play 49 waiting moves with their king. This gives 13 + 36 x 50 = 1813 moves. As moves 1814 and 1815, White does the following

```
[FEN "BBBB2k1/8/4NP1P/4P1N1/6P1/8/8/4K3 w - - 0 1"]

1. f7+ Kh8 2. f8=N Kg8

```

and then White makes 50 more waiting moves before drawing at move **1865**.
> 4 votes

# Answer
The answer is trivially the starting position -

```
[fen ""]

```

This exact question hasn't been asked before (I think) but it has been answered here. Here is the relevant part of that answer -

> The maximum number of moves in a chess game is not infinite, it's 11797 plies = 5898 moves and a half. This is due to the fifty-move rule.

As an interim possibility here is an obvious extension of the OP's original position (before he made dozens of edits):

```
[FEN "5b1k/p1p1p1p1/P1P1P1P1/8/8/8/P1P1P2P/RNBQKBNR w - - 0 1"]

```

White makes the same starting pawn and king moves as in the OP's post minus allowing any captures and then brings a piece out to capture the a pawn, taking 49 moves to do that, then queens one of the a pawns taking 49 moves per pawn move, then takes 49 moves to sacrifice that queen next to the king, then same again with white's other a pawn, ditto taking the c pawn, etc., etc.
> 6 votes

---
Tags: theory, problems, threefold-repetition, 50-move-rule, dead-position
---


# Question
Title: Making my own chess studies (like Lichess) with SCID vs PC
I am learning how to use SCID vs PC on my Linux machine and I find the program very useful and well-written. I am reading through Lasker's book *Manual of Chess* and I would like to create my own "studies' (to use the Lichess termiology) based on what I've read from the book (various defenses, openings etc.)

While I am able to use SCID to log into FICS, play against Stockfish, view famous games (using PGN files downloaded from www.chessgames.com) the one thing I cannot seem to be able to do is create my own study.

To be specific: sure, when open SCID I can shuffle pieces on the board according to how Lasker tells me to, and add annotations, variations, colored arrows and then save the resulting set of moves in a pgn file.

But once I want to start studying a new or opening, I don't want to have to create a NEW pgn file: I'd like to have a single PGN file containing, say, "chapters" as is done in Lichess studies. Is this possible?

Or are the SCID database files the way to go here? They seem a tad complicated at first glance.

# Answer
> 3 votes
Use a separate database per opening, book, or any topic you study. You can export that database later as a single PGN if you want. Imagine what happens if you don't do that: You have to store these games somewhere, right? And you really don't want those in your main database with normal games.

You can also copy games between databases, which is useful if you want to annotate a game and move it back to the main DB later. Don't worry about performance: A database doesn't take any resources (besides disc space) if you don't have it open.

As a bonus, and something that lichess doesn't offer: you can have as many "chapters" (games) as you want, and you can sort them, search for specific positions or comments, whatever you need.

---
Tags: study, scid
---


# Question
Title: Which side has the advantage in an Armageddon tiebreak game?
It is generally considered that white has better chances of winning in chess. This is due to white's initiative, since white gets to move first. The difference in chances seems to get more significant, as the level of play gets higher.

So, I suppose most grandmasters will choose to play white, whenever they are given the choice (especially in crucial games).

(1) What is the general view on the Armageddon tiebreak in that respect? Is there a clear preference in tournament play, or are white and black equally liked in Armageddon? What are opinions on this at the top level?

(2) Take the extreme example. In case of a tie after all classical, rapid and blitz games in a WCh match, there would be a drawing of lots, and the player who wins, gets to choose the colour in the Armageddon game. Which colour would be the choice of most GMs?

*Remark.* There are many variants of the Armageddon tiebreak. To avoid ambiguity, let us fix the time control used in the rules for the Anand-Carlsen WCh match 2014:

> The player with the white pieces shall receive 5 minutes, the player with the black pieces shall receive 4 minutes whereupon, after the 60th move, both players shall receive an increment of 3 seconds starting from move 61. In case of a draw the player with the black pieces is declared the winner.

# Answer
> 4 votes
> It is generally considered that white has better chances of winning in chess. This is due to white's initiative, since white gets to move first. The difference in chances seems to get more significant, as the level of play gets higher.

That is completely correct.

But in an armegeddon game the expected draw ratio is just as important as the white advantage and much more variable over playing strength and time controls. So the stronger the players and the longer the time control, the better it is to take black, because a draw becomes more likely.

To give a real life example: A few years back Gata Kamsky became US champ by playing the black pieces with 25 min on the clock against his opponent's 60 min. That's quite a different ratio compared to the Carlsen-Anand tiebreak time control … Kamsky's choice was justified by the rather long time control and the high level of competition. With a 2:1 time advantage I (a 2100 Elo player) would have taken white any day.

So there is a tradeoff between time control, playing strength and personal style in as much as they influence the expected draw ratio and the expected white advantage.

# Answer
> 11 votes
Armageddon Chess is a *fair* tie-break system only if the two players *bid* for how much time Black should have.

Foolishly most times I see Armageddon specified there is no bidding. Instead the Tournament Organizer gazes into his magic oracle which tells him the exactly correct fair amount of time to give to Black (the T.O. is careful to never let us see the oracle for ourselves). This no-bid foolishness amazes me.

# Answer
> 6 votes
There is a recent academic paper claiming that time controls in Armageddon of the 2018 World Chess Championship "*greatly favours black*"

# Answer
> 5 votes
If you ask this question to any FIDE officials they will answer you that nobody has advantage. Because ultimately, tiebreaks have to be fair. If it's not fair, then no one will want to play it.

However, in practical black has an advantage due to the psychological advantage to just hold the draw. In fact, to compensate this, there is a new system of players bidding for time in order to get the sides.

For example, if A and B is to play off against each other. They will have to offer the time they are willing to take in order to get black, A offers 3 minutes for black against white's 5 minute; B offers 4 minutes to play as black. Hence A wins the bid and the game proceed with 5 minutes for white, and 3 minutes for black.

Anyway, I haven't came across any statistics for armageddon tie breaks. But I am pretty sure that it depends on your style of playing to say that which side is advantageous. For an attacking player, white is obviously better, while for a defending player, black is probably a good choice.

# Answer
> 3 votes
I expand on GeneM's answer correctly noting that "Armageddon Chess is a *fair* tie-break system only if the two players bid for how much time Black should have.". (My additions are too long for a comment to that answer.)

An armageddon tiebreak with an *arbitrary, externally imposed* time penalty for the Black/draw-odds player is *not reliably fair* because it may grant an advantage to one of the players because there is no guarantee that the arbitrarily chosen time penalty is the correct amount to avoid undercompensating or overcompensating White for accepting must-win odds. (If the time penalty for Black is too high, it overcompensates White; if the time penalty for Black is too short, it undercompensates White.)

By having the players bid for the right to choose one's color, the arbitrariness is removed and the time penalty the Black player pays is one that that player voluntarily offered to pay. Thus armageddon with bidding is fair.

Bidding has been used in the past (e.g, in at least each of the 2013, 2014, 2015 and 2016 US Championships).

For example, in the regulations for the 2016 US Championships:

> An Armageddon Game is defined as a game with base time of 45 minutes for each Player. Black will have draw odds. Each Player shall bid an amount of time (minutes and seconds, a number equal to or less than 45:00) with which they are willing to play in order to choose their color. The Player who bids the lowest amount of time chooses his color and begins with that amount of time; the other Player receives 45:00. If both Players bid exactly the same amount of time, the Chief Arbiter will flip a coin to determine who shall choose their color.

As an example of how the bidding can unfold, in the 2013 US Championship the base time control was 45:00. Both players bid aggressively in hopes of getting the right to draw odds: GM Alejandro Ramirez (19:45) and GM Gata Kamsky (20:00). Ramirez' lower bid won, and he received Black with draw odds. Kamsky got the White pieces with the full 45:00 base time control but would have to win to survive. (Kamsky won the game and, with it, the US Championship for that year.) (Note that in this 2013 US Championship apparently the rule was that the winner of the bidding automatically gets Black. In later years of the US Championship, the rule was, properly, that the winner of the bidding could choose his color.) You can watch commentators GM Yasser Seirawan, GM Maurice Ashley, and WGM Jen Shahade discuss the bidding procedure and their thoughts about what each player should bid beginning around 30:32 of this YouTube video of coverage of the playoff round. The sealed bids are opened around 48:20.

It's not hard, nor does it take much time, to administer or implement such a bidding procedure, so I'm baffled why it's not used more in important tournaments.

Some additional notes:

* I say that an arbitrary time penalty is not *reliably* fair because, of course, it's possible that—by accident, in the same way that a broken clock is correct twice a day—the arbitrarily imposed time penalty may turn out to be the same penalty that bidding would result in.
* Some implementations (and even some of my examples and explanations above) assume that the player winning the bid automatically gets the Black pieces with draw odds. But that assumes that it's always the case that the benefit of draw odds for Black outweighs the disadvantage of moving second. There's no need to assume that. Instead, the winner of the bidding should be allowed to choose between (a) White with must-win odds and less time than Black or (b) Black with draw odds and less time than White.
* It would be superior if the rule were, instead of (a) the winning (i.e., lower) bidder gets his own bid on his clock (i.e., in this case Alejandro getting 19:45 on his clock), that (b) the winning bidder receives the *other player's* bid on the winning bidder's clock (i.e., Alejandro would get 20:00 minutes on his clock vs. 45:00 on Gata's). This would be a form of a second-price auction, which has the desirable property that each player has the incentive to bid his true value. (Otherwise, as in the 2013 US Championship, each player *A* has an incentive to try to outguess his opponent player *B* and just barely undercut *B*'s bid, even if in fact player *A* would have been willing to accept even less time in exchange for Black/draw-odds.)

---
Tags: statistics, time-control, armageddon
---


# Question
Title: Why is ...a6 played in the Exchange Slav?
```
[fen ""]
1. d4 d5 2. c4 c6 3. Nc3 Nf6 4. cxd5 cxd5 5. Bf4 Nc6 6. e3 a6

```

I do not see the point of this move. At first I thought it is aimed to prevent Bb5 and thus maintain the knight on c6, which controls e5, a square where White has a firm grip. It also prevents Nb5-c7, which is not yet a threat but might very well become one, as the White bishop is aiming at c7.

But after checking those threats aren't real and even if ...a6 is not played, in most continuations the best move for White is Bd3. Meanwhile the move ...a6 actually creates responsibilities (I would not yet say weaknesses, but work is required to avoid them) for Black, mainly because the advance ...b6 to control c5 leaves the queenside vulnerable (as demonstrated in Kramnik - Aronian 2012)

# Answer
> 5 votes
It prevents Nb5-c7. That's the main point behind the move. Just take a look at the disaster a careless move like 6...g6? could lead to.

6...a6 is not the only option, though. Black can try for instance 6...Bf5 (which is indeed more popular), intending to reply to 7.Nb5 with 7...Rc8. 6..e6 is another common move.

A good reason to prefer 6...a6 could be flexibility. 6...e6 makes it hard for the c8 bishop to find a good diagonal. 6...Bf5 could run into trouble against some Qb3

---
Tags: opening, slav-defense, queens-gambit-declined
---


# Question
Title: What is the shortest possible legal game where there are 6 pawns on the a-file or h-file?
I was recently reading a post on this forum which said that there must be 15 captured pieces in order for there to be 6 pawns on the a-file or h-file. That got me thinking how complicated that would be, which got me thinking how many moves would it take for such a thing to happen. So, what is the minimum length of a legal game (i.e. reachable from starting position) where there are 6 pawns **of the same color** on either the a-file or h-file?

# Answer
**31.0 moves** is optimal, as proven by @xnor on PSE.

```
[FEN ""]

1. Nf3 Nf6 2. Nd4 Nd5 3. Nc6 dxc6 4. g4 Bf5 5. gxf5 h5 6. f4 Nd7 7. e4 Ne5 8. fxe5 Qd6 9. exd6 exd6 10. exd5 g6 11. Na3 Bg7 12. Rb1 Bd4 13. h4 Bc5 14. d4 g5 15. hxg5 Rh6 16. dxc5 dxc5 17. Bd2 Re6+ 18. fxe6 fxe6 19. Ba6 exd5 20. c4 dxc4 21. Ba5 Ke7 22. b4 cxb4 23. g6 bxa3 24. Rb6 bxa6 25. Rxh5 cxb6 26. Rb5 bxa5 27. Qb3 cxb3 28. g7 bxa2 29. g8=Q cxb5 30. Qg4 Ke8 31. Qa4 bxa4

```

For fun, here is a related retrograde analysis problem. It shows the same effect, by piling six pawns on the e-file, but they do so in a unique move sequence. It has an entry in the Die Schwalbe Chess Problem Database.

```
[Title "Nicolas Dupont, Problemesis 06/2002, Proof Game In 20.5 Moves"]
[FEN ""]

1. h4 g5 2. hxg5 Nf6 3. gxf6 Bh6 4. fxe7 Be3 5. dxe3 b5 6. Qd6 b4 7. Qg3 b3 8. axb3 c5 9. Ra4 c4 10. bxc4 d5 11. cxd5 Be6 12. dxe6 Qd5 13. Rah4 Qf3 14. gxf3 Rg8 15. Bg2 Rg4 16. Kf1 Re4 17. fxe4 a5 18. f4 a4 19. Nf3 Ra5 20. Rg1 Re5 21. fxe5

```
> 5 votes

---
Tags: problems, pawns
---


# Question
Title: What is the probability that an exchange sacrifice leads to a win?
I seem to win a lot of games when I sac a rook for a bishop or a knight. Is this just me, or do exchange sacrifices often lead to a win?

I realize that any fool or noob can go overboard and do it all the time, but there are positions when it just feels right and they almost always lead to a win.

What guidance is there to better know when that sac of a rook for a minor piece is likely to pay off?

# Answer
> 1 votes
In my experience, it's best to just check what it gives, for example: if I now sacrifice my legs and in return all my tools will be active and the opponent's passive, then it's right to sacrifice my legs, every time I have to act like math, feet equal point, activity equal 1.2, direct attack On the king is worth 1.3, and so on, everyone has to decide for him what is worth to him an attack on the king, what is worth my feet, and thus decide whether to sacrifice or not. Hope I helped

---
Tags: learning, sacrifice
---


title: Bishop sacrifices to prevent castling

text:
# Question
Title: Bishop sacrifices to prevent castling
I have neen playing a higher amount of online chess as opposed to club chess lately and something I have noticed is a significant increase in Bishop sacrifices to prevent kingside castling. Here is an example.

```
rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1
1. e4 e5 2. Bc4 Nf6 3. Nf3 Nc6 4. O-O Bc5 5. Bxf7+

```

The above is probably the most common instance I have come across of this "tactic" being used..Is sacrificing the minor piece really worth it? Is there name for this tactic, eg "Fianchetto"?

# Answer
Not worth it.

Tactic used by low rated players which might work against other low rated players but would fail to a halfway decent player.

Run the position through an engine of your choice and see what it says.

No official name but patzer fish rookie beginner could work.

Can not comment.
@David Bateman: If those ratings are online then they are barely getting out of the beginner rating class.
> 6 votes

# Answer
The reason bishops are sacrificed is that they are the least likely to be stopped from being sacrificed, compared to a knight or a pawn for whom the a6 / h6 takes 4 moves. The bishop sacrifice is usually not stopped from a direct threat to the king (except for the French Defence),

Another reason: a bishop sacrifice opens up the opponent's king more. Also your pawns in front of the opposing king when they are active and the opponent's pawns on the other side passive it can be successful because you have compensation.

> Is sacrificing the minor piece really worth it?

As long as it will be possible to stop the attack without any damage, it is clearly not worth it. In the example above it's a really bad sacrifice. Your pawns are not threatening the king and neither side has completed development.
> -1 votes

---
Tags: tactics, terminology, bishops, sacrifice
---


# Question
Title: What was Anand thinking in the 1994 Armageddon blitz semifinal?
In the famous Blitz semifinal armageddon in 1994, Anand spends 1:43 minutes (from his 5 minutes available) on move 4, and ends up winning the game.

What exactly was he thinking? Are there any interviews (text, sound or video) available where he elaborates on his thought process?

```
[Title "Smirin - Anand, 1994"]
[Event "New York PCA/Intel-GP"]
[Site "New York, NY USA"]
[Date "1994.06.??"]
[Result "0-1"]
[White "Ilya Yulyevich Smirin"]
[Black "Viswanathan Anand"]
[ECO "C42"]
[PlyCount "100"]
[fen ""]
[startply "7"]

1. e4 e5 2. Nf3 Nf6 3. d4 Nxe4 4. Nxe5 {Here, Anand thinks for 1:43 minutes}
d6 5.Nf3 d5 6.Bd3 Nc6 7.O-O
Be7 8.c4 Nb4 9.Be2 Be6 10.Nc3 O-O 11.Be3 Bf5 12.Rc1 dxc4
13.Bxc4 c6 14.Ne5 Nxc3 15.bxc3 Nd5 16.Qb3 f6 17.Qxb7 fxe5
18.Qxc6 Be4 19.dxe5 Kh8 20.Bd4 Rc8 21.Qa6 Nf4 22.f3 Rc6 23.Qa4
Rxc4 24.Qxc4 Bd3 25.Qc6 Ne2+ 26.Kh1 Nxd4 27.cxd4 Bxf1 28.Rxf1
Qxd4 29.f4 Qxe5 30.g3 Qc5 31.Qe4 Bf6 32.Kg2 Rc8 33.Rf2 Qc6
34.Qxc6 Rxc6 35.g4 h6 36.Kf3 Rc3+ 37.Ke4 Kh7 38.Re2 Rc4+
39.Kf5 Rc5+ 40.Ke6 Rc4 41.Rf2 Kg6 42.h3 Rc3 43.Rh2 Rf3 44.f5
Kg5 45.a4 Kh4 46.Kd5 Ra3 47.Kc6 Rxa4 48.Kb7 a5 49.Kb6 Ra3
50.Kb5 Rxh3 0-1

```

# Answer
> 22 votes
From a YouTube comment section dedicated to the game (I did not find the primary source, so it may be untrue):

> Anand was asked about this in the interview after. Smirin did not play the opening Anand was expecting. In a finale like this, White must win and so will play something dangerous to avoid Black forcing a simple draw. When Anand saw that Smirin was deviating from his usual opening, he says that he stopped to think what players and tournaments Smirin had been in recently. He was trying to figure out if there was some new trap or opening that had been developed recently using that move. Once he had an idea what Smirin was going for (which could have been ten moves out), he decided what opening he would play to avoid that line.
>
> The plan worked. Anand was able to prevent Smirin from getting any momentum in his attack. He sacrificed a piece to try to get a clear path for his center pawns (to try to queen one of them), but Anand was able to trade away enough pieces that Smirin couldn't keep the position active enough to win.

---
Tags: blitz, calculation, anand, petroff-defense
---


title: Is Stockfish 11 SuFi 19 still fallible?

text:
# Question
Title: Is Stockfish 11 SuFi 19 still fallible?
In a Game of SuFi 19 , a Czech Benoni, Stockfish 11 as White could have forced , on move 28 , a line that forced an eight piece endgame on move 59. White would have had Queen , Knight and two advanced pawns vs Queen and Rook . The line was suggested by Stockfish own PV on move 27 , a plan that later abandoned for a small centipawn difference. In the game Stockfish was pressing hard in a pawn up endgame , but cannot overcame the stubborn defense by Leela zero ( at least in that game) and the game ended in a draw. Since I have extensively analyzed the eight piece endgame described above with Houdini 6.02 at d= 38/128 and concluded that it was a win, it should be concluded that Stockfish 11 took the wrong path on move 28. The game was a Czech Benoni defense, and , to be honest , is the only mistake by Stockfish 11 in the current SuFi when Stockfish was not in time trouble. Game 62 SuFi 19. At least even Stockfish 11 is not infallible!

# Answer
Perhaps worth starting by explaining for the benefit of the majority of chess fans who have no interest in computer chess tournaments that a "game of SuFi 19" is not some new chess variant. "SuFi" stands for "Super Final" and "SuFi 19" is the 2019 computer chess super final tournament.

> Is Stockfish 11 SuFi 19 still fallible?

It's also worth reminding ourselves of the meaning of the word "fallible" and its opposite, "infallible".

"Infallible" means "never makes a mistake" and "fallible" means "makes mistakes".

We are still a very long way away from the day that chess will be solved and so are still a long way away from the day that a chess engine is infallible. Until then all chess engines are fallible. In particular Stockfish 11 is fallible.
> 2 votes

---
Tags: engines
---