# Question
Title: Given a legal chess position, is there an algorithm that generates a series of moves that lead to it?
Given a FEN board position, is there an algorithm that can return a PGN move list that evaluates to it from the standard initial position?

# Answer
The task you are considered is usually called a proof game, named such because the task is to *prove* that the position is legal. As a genre of puzzles, there are various aesthetic constraints, most commonly that the resulting game be unique. However, this is not necessary in general, and there is even a genre of counting the number of solutions.

There are several programs available that perform this task of solving proof games:

1. Natch is often considered the fastest. You can see it in use in this answer to another question on this site: "Can it be proven that 11. 0-0-0+ is legal in this position?"
2. Euclide is apparently most useful when the sequence of moves is unique.
3. Popeye can solve many chess problems, including fairy chess problems. Apparently it is not the most performant for proof games.
4. Jacobi is a program to solve (fairy) chess proof game problems. It is written in JavaScript and run from browser, which makes it easy to try.

I have used Natch most successfully myself.
> 31 votes

# Answer
If you are familiar with mathematical induction then it should be clear to you that the answer is trivially "Yes".

Just as for any position (legal or otherwise) it is possible to use the laws of chess to calculate all the legal moves in that position (this is what computer engines do) so given any position (legal or otherwise), P(n), other than the start position and a side, S(n), either black or white, it is possible to calculate all the possible previous legal moves for player S(n). This will likely give many new positions (some may be illegal), P(n-1).

If P(n-1) is the empty set then we know that P(n) was an illegal position. If P(n-1) is not the empty set then set S(n-1) to the opposite of S(n) and repeat the previous step for all elements of P(n-1) for player S(n-1).

If the original position was legal then this induction process will terminate with the initial position. If the original position was not legal then it will terminate with some other position.
> 10 votes

# Answer
The natural approach to this problem is a tablebase-like approach like outlined by Brian. But doing something similar to that for just 7 pieces (namely, 7 men tablebases) with current algorithms already takes many months of calculation and 1 Tera Byte of RAM, doing that and trying to get to the starting position sounds pretty impossible. (otherwise one may just as well try to solve chess by building a 32 men TB)

In general I strongly suspect this problem is NP hard. However in practice the following human-like approach should work for most positions: Determine which pieces are missing from either side and evaluate how many captures are necessary to form the given pawn structure. (e.g. you need at least one capture to create a doubled pawn) Based on that, create "paths" that the pawns might have taken to reach the current pawn structure. Then try to move the to be captured pieces on that path to be captured by pawns if necessary. Move the remaining pieces on their squares.

The reason why this will work most of the time is that the only irreversible moves are captures and pawn moves (this is not quite true, but close enough for this explanation). Therefore, the shuffling of other pieces does not need to be exact, there are many ways to bring some piece to some other square. (but there may only be one way to get a pawn to a certain square)

For most "real life" examples this should work well enough. Things will get more complicated, once you require promotions or specific move orders (for instance because some piece is locked in by pawns and the piece and pawn movements must be coordinated to achieve that position). Also, if 50 moves rule becomes a factor because in that case it might matter which path pieces choose. Nonetheless for most practical positions that is not an issue.

Even for those difficult positions I still think human like approaches might be useful. The following is very vague, but I think what could work is trying to determine certain scenarios that must have happened. For a contrived example, consider a position white Bf8, black Pg7 Pe7. The bishop can not have moved there since the pawns are on g7 and e7 still. So it must have come from a promotion of the f pawn.

Accumulate all relevant scenarios, determine which are dependent and try to put them in some order that makes it work. In practice you will fail here for some positions but such is the nature of NP hard problems. More specifically, I suspect that for every algorithm you devise, there will be some position that you can't solve with current computing power.
> 6 votes

---
Tags: analysis, programming, retrograde-analysis, calculation, chess-algorithms
---


# Question
Title: Which engine is better at Chess960-Stockfish or Leela?
It seems that TCEC has seen Stockfish and Leela go back and forth. It is probable that these days Stockfish is a little bit better than Leela. I was wondering, since it is different in Chess960, which one of two is better at it? Does anyone have any insights?

# Answer
> 4 votes
Currently, it's Stockfish: in the latest FRC exhibition (November 2020) Stockfish beat Leela +8 -0 =42.

# Answer
> -2 votes
Leela or AlphaZero is the best computer since they have beaten Stockfish in standard chess and Leela is said to be better at positional chess than Stockfish. Stockfish is better at tactical chess and since Chess960 is more positional than standard chess, Leela (or AlphaZero) is better at Chess960.

---
Tags: engines, stockfish, chess960, leela
---


title: Lc0 vs. Stockfish

text:
# Question
Title: Lc0 vs. Stockfish
Stockfish analyses many positions per second and chooses the best line. Lc0 is a neural network that immediately ignores moves which don't work, but is slower. However, somehow Stockfish is better. How come that is true, when most of the positions it looks through are actually useless?

# Answer
> -4 votes
This is due to the way Neural Networks AI works; Neural networks can only make decisions based off prior experience where as StockFish is more or less "Brute Forces" and prunes until the maximum numerical value is gained.

Theoretically if you could feed an AI like Lc0 enough game data (potentially the Chess Base Big Database) , especially with additional data like stockfish position evaluations you could create quite a powerful neural network with the ability to self move etc;

I think Lc0 could have the potential to develop new ideas; however it would require a secondary database of evaluations and scoring to determine it.

# Answer
> 7 votes
**Because Stockfish searches a LOT more positions.**

Just check the latest TCEC superfinal between the two. In a typical position Leela might search 40k positions per second. Comparatively, Stockfish searches ~200 million positions per second. That's about 5000 times more positions per second. It means that Stockfish can afford to be wrong 4999 times as long as it searches the moves that are right. (This is of course simplified since it assumes there is a "right" move.)

Also worth pointing out is that it is by no means obvious that selectively searching the "best" moves is a better approach than simply searching tons and tons of them. Remember several decades ago when computer chess was new, there were two ways to approach search. The first was to get computers to "think" like humans and consider only the best candidate moves. The other, and the one that eventually came to dominate, is to search as many moves as possible. You can see similar tensions in the real world: humans only have a few babies, but some species (such as ferns) have lots of children, most of which die, but those that survive propagate the species successfully.

Finally, one should note that Leela's neural network is not always right. See this Leela blunder vs. GM Andrew Tang, along with an explanation of why Leela blundered.

> But how come Leela blundered such a simple tactic? Looking at the chess clocks, we can see that Leela spent less than 0.1 seconds thinking before making the move. Under such time constraints, Leela is not really able to consider and evaluate many different moves, but instead relies heavily on her "instincts". Looking under the hood after the match, we could see that Leela thinks Qxd4 is the correct move 90% of the time in the critical position. Furthermore, Leela thinks Bh7+ is the correct reply only 10% of the time. If she had more time to double check her assumptions, she would not have blundered, but she didn't - so she did. In our estimation, Leela would have avoided the blunder if she had spent 0.25 seconds thinking before making a a move.

As this paragraph shows, Leela's instincts are not always right. Leela compensates for this by searching the other moves anyway, it just searches them less. If Leela really did ignore "moves that don't work", it would be decisively lose repeatedly.

# Answer
> 1 votes
I'll expand on a few things that Allure already mentioned: From the question: "Stockfish analyses many positions per second and chooses the best line. Lc0 is a neural network that immediately ignores moves which don't work, but is slower."

This is not really true. Leela and Stockfish are more similar than some people seem to assume: Both will eventually look at all moves. However both spend varying amounts of time on different moves, i.e., they will spend more time on moves they think are good. The difference between the two is: Stockfish uses "humanly chosen" heuristics (of course those are also tuned, but they are still based on human ideas) to determine which move to search how much, while Leela uses a neural network to determine which move to search how much. Both engines then search that move and based on the results (that is, the evaluation) decide how much to search that move moving forward. (obviously, the better a move the more it will be searched)

The other difference is the search backup, Stockfish uses a minimax based backup, meaning it's evaluation of a line is exactly the evaluation of the final position of that assumed best variation. Meanwhile Leela uses an averaging based backup, meaning also evaluations from positions that are not part of the best line can influence the evaluation. This latter algorithm is not really possible with Stockfish since it requires storing the entire search tree, which given Stockfish's speed isn't possible. However due to the lower nodes per second of Leela because of the NN, it is possible there. Which of the two is preferable is debatable, Leela's search algorithm does have some issues.

Of course new versions of Stockfish now also use a NN, albeit one with a very different structure. That doesn't really change the answer at all though.

# Answer
> -4 votes
The simple (oversimple) answer is that Stockfish considers *all* moves whereas Lc0 only considers moves/positions it has in its database/neural network. In a sense Lc0 can't find new ideas whereas Stockfish can.

---
Tags: engines, analysis, stockfish
---


# Question
Title: Did Stockfish regress from October to December 2020? If so, why?
NCM data

If the NCM data is to be believed, somewhere around October 2020, Stockfish dev hit +370 elo vs. Stockfish 7, but has since regressed to only +360. What's going on?

Only thing I can think of is a statistical fluctuation, which is plausible since the error bars are +/- 5. However, the gap between the October ratings and the current ones appear to be too large to fully attribute to statistics. This is especially the case if we believe Stockfish improved between October and December (which it presumably must have since engines are constantly improving). On the other hand, if the October versions of Stockfish are truly stronger than the latest ones, the newer versions ought not to have been accepted.

# Answer
> 21 votes
It is of course always possible that Stockfish did regress. The way changes are tested for Stockfish, or most engines for that matter, always allows for regressions to pass some of the time. (you simply can't play long enough test matches in reasonable time to be very sure that you don't regress) This is not much of an issue since most of the time you will detect which changes brought improvement and which did not. However you can "run unlucky" and hit a couple not so good changes in a row. In fact I do recall an instant when Stockfish was reverted a number of commits since such a regression was measured.

However, in this case if the tests were run against Stockfish 7. I think a more likely explanation may simply be that the newer Stockfish did slightly worse against that specific opponent. Strength is not absolute, you can be better against some opponents and worse against others. The interesting thing then of course is to be on average stronger than the older version however that can still allow an engine to be weaker against certain opponents. Especially, if like the case here, the opponent is several hundred points weaker. At that point it is less about playing the absolute best move and more about beating up the much weaker opponent more efficiently. And especially since the supposed regression is only 10 rating points, I wouldn't interpret too much into it.

---
Tags: engines, stockfish
---


# Question
Title: Can a pawn move to the last row diagonally without a capture?
Playing the "Champion" J2ME chess, I noticed that the bot (black) made the move "Pg2-h1=Q." Is this a bug or just a rarely known rule like en passant and castling?

# Answer
Pawns only go diagonally when they capture. See the section 3.7 of Chess rules.

The software you mention probably has a flaw.
> 8 votes

# Answer
Not a bug, it's an entirely possible move. (at least on chess titans.) Chess titans is the windows 7 version of chess.
> -2 votes

---
Tags: rules, pawns, pawn-promotion
---


title: Retrograde analysis problem

text:
# Question
Title: Retrograde analysis problem
Given that this position is legal, and could be reached in a legal game of chess, what were the two last half-movess, or one move for White and one for Black?

```
[FEN "5K2/8/6Pk/8/5Q1R/8/8/8 w - - 0 1"]

```

P.S.: I don't know the source. If someone knows the author, please say so and I will make an edit.

# Answer
The Black king is in check from both the White rook and queen, so it's impossible that either piece moved to give a check, it must have been a discovered check on the last move, which makes the White pawn on g6 the likely piece that was last moved.

White's last move must have been hxg6 en-passant. Which makes Black's previous move g7-g5 to block the check from the White queen.
> 8 votes

---
Tags: problems, retrograde-analysis
---


# Question
Title: Do any grandmasters win more with black than white?
Some statistics indicate white scores 52-56% \- but I wonder if that differs according to playing style - e.g. perhaps strong defenders prefer the black pieces.

Do any former/current grandmasters have stronger win records with the black pieces than with white?

Note: the reason for choosing only grandmasters in this question is simply to ensure a large number of games had been recorded for the player so as to exclude any player who only played a small number of games

# Answer
> 21 votes
## The short answer

Yes, they do, although very few GMs do and by a margin of less than 10%. This does not seem to be due only to random factors (see long answer).

An example is GM Joseph Gallagher. As you can see in his FIDE profile page, he has the following games record (as for 15 Dec. 2020):

```
White +124 =118 -73, score = 58.1%
Black +126 =124 -67, score = 59.3%

```

## The long answer

To obtain the figure above I used the games published by TWIC, issues 920-1358 (25 Jun. 2012 to 16 Nov. 2020). I selected games where at least one of the players was a GM. And I kept only players with more than 50 games per color in the dataset. This ensures that scores are calculated with a 90% confidence interval of at least ±2%, and, since players in the dataset have in average a couple of hundred games, scores are usually still more accurate. The resulting dataset had 561K games for 1168 GM players.

In this case, the average scores where 65.5% for white and 56.9% for black. This is higher than in the databases you mention because being a GM most other players have a lower rating and they're more likely to win. (If I took only the games where both players were GMs, the average scores were 52.9% for white and 43.3% for black.)

As shown in the figure above, the average difference of scores between both colors is 8.6%, favorable to white. Still, there were 38 players who had better results overall with black. The five players with the highest difference in performance favorable to black in the dataset were:

```
                    WhiteScore  BlackScore  Difference
Bryan Smith            55.2        62.9        7.8
Essam El Gindy         52.0        58.8        6.9
Jean-Luc Chabanon      50.5        57.2        6.7
Justin Tan             54.5        61.2        6.7
Mihai Suba             57.9        63.8        5.9

```

I would like to bring your attention to one of these players, Mihai Suba, who is known for his book *Dynamic Chess Strategy*. In it he disagrees with white's first move advantage theory.

**Note:** If you look at these players' FIDE profile pages, you might find some discrepancies, due to the different characteristics of both datasets. The FIDE data includes all FIDE rated games (whether the player was already a GM or not); while my dataset contains games published on TWIC (FIDE rated or not) from 2012 to 2020 only if the player was already a GM.

## But is it a correct answer?

Now, just because of randomness we would expect that some players had better results with black than with white. But is it the case? Do those players really perform better with black pieces or is it simply a random illusion? To check this I plotted the evolution of the score difference as the number of games increases for several players.

As you can see, the score difference varies widely when there are few games. But as the number of games increases, the variability decreases. In some cases, the score difference remains consistently above 0. In other cases, it occasionally crosses the line.

So, yes, there are some cases that cannot be considered a statistical artifact.

## And what about differences in style?

You didn't really ask about it, but since you mentioned it in your question I had a look at it. For this I divided the players in three groups according to their score difference:

* Upper 5%: Mostly players with better results with black
* Lower 5%: Players with much better results with white
* Those in the middle

And then I looked which kinds of openings they used, classified according to the five main ECO categories:

* A: Flank openings
* B: Semi-Open Games other than the French Defense
* C: Open Games and the French Defense
* D: Closed Games and Semi-Closed Games
* E: Indian Defenses

It would seem that GMs who have better results with black pieces tend to use openings of the groups A and B more often than the other players, and the other groups less often. Although more detailed analyses would be necessary to arrive at more solid conclusions, this can give you some food for thought.

## Update 19/02/2020

### Dataset and script

Following the request by @stevec, I have shared the dataset and script used to write this answer on github. It can be used to investigate some of the proposals made by other users (@HaukeReddmann, @SecretAgentMan) in the comments.

### Further tests

@Grade'Eh'Bacon, suggested in a comment comparing the observed distribution of the difference in scores to the expected distribution under only random influences. I had already done this analysis, but I decided not to include it because the answer was rather long. But since it has been requested, I share it here.

If the distribution shown in the score differences plot at the top of the answer was due only to random factors, we would expect a normal distribution (aka Gaussian distribution, bell curve). This is the hypothesis assumed in Elo calculations and can be checked with a Monte Carlo simulation.

One way to test if a variable follows a normal distribution is with a Q-Q plot (see below). If the observed score difference followed a normal distribution, the points would be close to the diagonal line. This happens in the middle zone, but not in the extremes. We have a distribution with heavy tails, that is, there are too many players with better results with black and too many players with much better results with white to be due to random causes alone.

The results of the Shapiro-Wilks test, which is also used to test for normality is also consistent with the hypothesis that the distribution is not normal. This supports the hypothesis that there is something else going on apart from randomness.

And I also repeated the analysis with another independent dataset of games from the ICCF. And I obtained comparable results.

# Answer
> 13 votes
White scores about 54%, which is quite different from White winning 54% of all game, more so considering how draws occur more often between stronger players.

None of the top players score better as Black, and I doubt there are grandmasters who do. If that were the case, it'd definitely be due to a small sample. I used to have a better score as Black back when I was an 1800-rated player, but it soon got corrected.

---
Tags: statistics, grandmaster, pieces
---


# Question
Title: What is this opening trap I keep encountering in the Englund Gambit?
```
[FEN ""]

1. d4 e5 { A40 Englund Gambit } 2. dxe5 Bc5 3. Nc3 b5 4. Nxb5 d6 5. exd6 Ne7 6. dxe7 Bxf2+ 7. Kxf2 Qxd1 8. Na3 Kxe7 9. Nf3 Qd6 10. Nb5 Qc6 11. a4 Qxc2 12. g3 Qc3 13. Nxc3 { Black resigns. } 1-0

```

I have suddenly encountered very similar opening lines several times in the past few days, where I play d4, my opponent plays the englund e5, I take the pawn, then take another pawn or piece with that pawn as they move their bishop out, then my opponent sacrifices their bishop to draw out my king and allow a queen queen capture. Is their a name for this opening trap? Lichess doesn't recognize it.

# Answer
> 5 votes
# This is just a series of bad moves by black.

The video linked to by koedem says it's a new "trap," and quite frankly, it requires white to resign after dropping the queen to qualify as a trap. If white continues 8. Nxc7+, when the dust settles, white still has a slight advantage, having traded a queen for a rook, two pawns and a bishop. (In this continuation, white will exchange the knight for a rook and lose the pawn on e7.)

If white plays 6. Nxc7+ and captures the knight before capturing the rook, white ends up winning a rook and two pawns outright, and remove's black's castling rights. So black is taking the risk of a crushing loss in the hopes that white will blunder his way into equality instead.

---
Tags: opening, opening-traps
---


title: 3...c5 in the Advance Caro-Kann

text:
# Question
Title: 3...c5 in the Advance Caro-Kann
Consider the following side line of the Advance Caro-Kann:

```
[FEN ""]
1.e4 c6 2.d4 d5 3.e5 c5 4.dxc5 e6 5.a3 Bxc5

```

In master OTB games, the move 3...c5 is one third as common as the main move ...Bf5. The main justification I have heard for this is that black is immediately conceding to a lost tempo by having first played first ...c6 and only then playing ...c5. I contend that this justification makes no sense, for two reasons:

(1) In the main line after 3...c5, black immediately regains the tempo when he recaptures with the bishop on c5. True, white can himself gain a tempo on the bishop with b4, but it is at least questionable whether this is the best move in the position.

(2) Even if we grant that black doesn't really regain the tempo because the bishop will have to move again, the fact remains that in the lines after ...Bf5, black still needs to play ...c5 at some point. But whenever he plays it, he will still be losing a tempo. Where is the harm losing this tempo on move three rather than on some later move?

So my question is: is the 'lost tempo' really the reason why 3...Bf5 is preferred to 3...c5?

# Answer
> 2 votes
I believe 3...Bf5 is preferred is because they want to play a Caro-Kann and not the French defense. Black's main problem with his position after 4...e6 is the Bishop on c8. White still has all his pieces on the first rank while Black has a Bishop developed so any loss of tempo is not really an issue here.

---
Tags: opening, theory, caro-kann
---


title: Do you know this proof game?

text:
# Question
Title: Do you know this proof game?
I'm not familiar with this proof game.

```
[FEN "r2qk1nr/ppp1pp1p/2n1p2p/8/8/1P6/NPPPPPPP/R3K2R w KQkq - 0 1"]

```

What square was the white queen captured and how?

# Answer
> 9 votes
> The White Queen was captured on h6 by the Black Pawn.

The reasoning is as follows:

> * It is impossible for both White bishops to move from their start squares, so they were both captured by Black knights.

> * White's other two missing pieces are a knight and the queen. Black has two displaced pawns that are there as the result of captures (pawn on e6 and h6), So both of those pawns captured White pieces.

> * Essentially the White queen developed from it's d1 start square to b1-a2 and then outside of White's pawn chain

> * Which means the question is how did White's pawn get from a2 to b3. Black has no pawns missing. The Black queen and both knights are on the board, which means White's pawn capture of a2 to b3 was capturing the Black light-squared bishop (which started on c8).

> * But, how did Black's bishop get from c8 to b3? Via the d7-square, which is unblocked by the black pawn capture d7xe6. That capture must have been of the missing White knight, because the White queen couldn't get to e6 to unblock the black dark-squared bishop.

So the time series of key events:

> * Black's knights marauded around the board capturing both White bishops on their start squares, and returned to g8 and c6

> * White's knight got to e6 and was captured by the black pawn on d7, thus allowing the Black light-squared bishop to develop. The other knight stayed on the queenside. One of White's knights captured the black dark-squared bishop on f8.

> * Black's now freed bishop landed on b3, and was captured by the a2 pawn. This freed the White Queen

> * The White queen developed via b1 and a2, reached h6 and was captured by the Black pawn on g7.

---
Tags: problems, retrograde-analysis
---


title: Chess engine does not go for checkmate

text:
# Question
Title: Chess engine does not go for checkmate
I have made a chess engine that can play a decent game of chess. Like a lot of engines it uses a minimax search algorithm with alpha-beta pruning. It uses this simple evaluation function to assign a score. The problem I have is that the engine does not attempt to go for checkmate. Against Stockfish, it will attempt to capture all the enemy pieces and then get a queen via pawn promotion, presumably to maximize its score. It sometimes stumbles upon a mate position, but it is more common to result in stalemate even with multiple pieces (queen, rooks, bishops) vs a lone king. I think this is because my algorithm currently only encourages maximizing the difference in score (white vs black) and has no concept of mate. One idea I had is increasing the piece value of the king to encourage mate. Are there any methods to encourage the engine to go for mate rather than a massive material imbalance?

# Answer
> 4 votes
> Are there any methods to encourage the engine to go for mate rather than a massive material imbalance?

Any reasonably sophisticated position evaluation function is going to give extra points for certain positional elements (passed pawns, advanced pawns, bishop pair, etc.) and deduct points for other negative positional elements (doubled pawns, isolated pawns, bad bishop, unsafe king, etc)

Obviously any halfway decent evaluation function is also going to handle positional elements like checkmate (add MAXINT), stalemate (assign 0.0), 3-fold repetition (0.0), 50 move rule (0.0), insufficient material (0.0), etc.

If all your evaluation function does is use piece values and nothing else then you still have a lot of work to do to have an engine that is any good.

---
Tags: engines, checkmate, computer-chess
---


# Question
Title: As a beginner, how do I learn to win in "won" positions?
I'm fairly new to chess (~3 months) and I have almost entirely been playing on chess.com where my rating sits somewhere between 1000 and 1100. Recently, I decided to sign up for lichess.org, where I was placed at ~1650 as I haven't played many games yet, and unsurprisingly I lose quite often.

But facing higher rated players made me realise I don't know how to win a game of chess.

On chess.com, the people I face will almost always trade pieces if offered, so if I have a material advantage it is very easy to trade off all other pieces then staircase checkmate and win. Facing higher rated players on lichess made me realise that if they don't cooperate like this I have no idea what to do. I know I sound pretty stupid here but somehow I have just never had a game like this before.

In this game, by the end Stockfish says it was -3.1 (I played the black pieces) when my opponent lost on time, but if they didn't, I have no idea how I was going to win if they didn't at least trade queens.

```
[Event "Rated Rapid game"]
[FEN ""]
[StartFlipped "1"]
[Date "2020.12.13"]
[White ""]
[Black "Me"]
[Result "0-1"]
[UTCDate "2020.12.13"]
[UTCTime "08:02:31"]
[WhiteElo "1655"]
[BlackElo "1645"]
[WhiteRatingDiff "-6"]
[BlackRatingDiff "+10"]
[Variant "Standard"]
[TimeControl "600+5"]
[ECO "C48"]
[Opening "Four Knights Game: Spanish Variation, Classical Variation"]
[Termination "Time forfeit"]

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Bb5 Bc5 5. O-O a6 6. Ba4 b5 7. Bb3 O-O 8. a3 Bb7 9. Re1 Ng4 10. Rf1 Nd4 11. Ba2 Nxf3+ 12. Qxf3 Qh4 13. h3 Nf6 14. b4 Bd4 15. Bb2 Bxe4 16. Qe2 Bxc3 17. Bxc3 Qg5 18. f3 Bxc2 19. d4 Qg6 20. dxe5 Bd3 21. Qb2 Bxf1 22. Rxf1 Ne8 23. f4 Qb6+ 24. Bd4 Qc6 25. Rc1 Qh6 26. Be3 d6 27. exd6 Nxd6 28. Rxc7 Rac8 29. Ra7 Ra8 30. Qf2 Rxa7 31. Bxa7 Qf6 32. Bd4 Qh6 33. f5 Qc1+ 34. Kh2 Nc4 0-1

```

So I'm not really looking for somebody to tell me the best continuation of this game so I could win, but is this a problem with playing too passively? As in, "I should be actively attacking the king more" is my assumption, but I'm unsure how to learn about how to do that. I came across Vukovic's *Art of Attack in Chess* when searching online but according to the /r/chess wiki that book is for 1800-2000 rated players. So my question is what should I be focusing on to be able to win in these positions?

# Answer
There are two key things you need to do.

The first is to know how to win a won endgame. You do that by studying endgames. That will do two important things for you. Apart from teaching you how to win a won endgame, it will also teach you to recognise which endgame positions are won, and which are drawn, despite your material advantage. That way when you are in a winning middlegame you know what kind of endgame you are aiming for.

The second really important thing to do is to keep on fighting. The aim is not to get a winning middlegame position, it is to win the game. To that end a winning middlegame position is just one stop on the way to your real desired destination.

If you are driving to visit friends or family and you stop two thirds of the way there for petrol (or gas if you live in the US) you don't stop because you think you have arrived. You carry on after the stop, in just the same way as you did before the stop, except that you are no longer worried that you are going to run out of fuel (or not win the game).

This tendency to sit back once you have a theoretically winning position is something which affects all players. You have to fight it by trying even harder to not let your opponent back into the game and to win it yourself. Perhaps one good way of doing this is by starting each think about your next move by asking yourself "Why did my opponent do that? What are they trying to do? How can I stop them?"
> 26 votes

# Answer
I remember reading about this from one of GM Yasser Seirawan's books. What you want to do is:

* Pick a target
* Figure out how to attack it

In this case the obvious target is the White pawn on a3. Why this pawn? Because it cannot move (a4 bxa4 wins the pawn). It stands to reason it's easier to attack something that cannot move. The a3-pawn is also not easy to defend - it can no longer be defended by a pawn, so it must be defended by pieces, and you have more powerful pieces.

Your last move 34...Nc4 accomplishes this goal of hitting the pawn. White can't defend it anymore. Next turn, you play 35...Nxa3 which increases your material advantage, and now you pick a new target - this time the pawn on b4. The reason is the same, it cannot move and it cannot be defended by a White pawn. Once you have identified the target it becomes easy to plan how to take it: you play ...Rc4, ...Nc6, ...Qb1, etc, and then you will have more attackers than White has defenders. After you grab the b4-pawn you have powerful connected passed pawns that you can shepherd to promotion & victory.

Note this analysis is superficial - 35.a4 bxa4?? actually loses you most of your advantage according to Stockfish - but that is because of the specifics of the position (in this case, White's bishops are actually quite threatening to your King).

One more thing: because you are ahead in material, another powerful plan is to force trades. Your opponent will be trying their darnedest not to acquiesce, but a material advantage lets you create threats that your opponent cannot parry. In the final position for example, an immediate threat you have is ...Qd2. If opponent does not trade queens, you take the bishop on a2. If White plays 35.Qg3 for example, then ...Qc2 traps the bishop and forces another trade (of course, you will have to defend against the threatened Qxg7# first).
> 18 votes

# Answer
**First consider the difference between a 'truly' won position vs a 'theoretically winning' position**. By that I mean - a position that is within your own abilities to convert to a win, in a way you can already see, vs a position that seems like it 'should be winning'. You see that stockfish says the position was -3.1, but at your rating level, -3.1 isn't 'truly' won - first of course because you point out that you can't see how to convert it, and second simply because at your current level, it would be very natural to overlook a tactic that you or your opponent could perform with a larger impact than a 3 point material swing.

So move away from calling a position like this 'won'; it could lead you to let your guard down. At the same time, a 3 point advantage 'should' be enough to convert to a win *with perfect play*, in most cases.

**So what gets in the way of you converting this 'theoretically winning' position to a 'truly won' position? Complexity.** Particularly at your level of play, but really in all levels of chess, complexity and asymmetry *is an advantage to the player on the backfoot*.

Imagine an endgame where you have a rook and nothing else, and I just have a king. This should be a 100% won game (and if you don't consider that completely won, work on your endgames, so that you can convert a win in any circumstance where your opponent has only a bare king, and you have a minimum of material). Now now add 2 pawns and a knight for each of us to the board. Where before you would be able to easily slide your rook away from my king and make the mechanical advance that leads to checkmate, now you need to be cautious - are my pawns able to make a break for the 8th rank? Can my knight fork your rook and king? Is your knight trapped by the position of your own pieces? \**Complexity has created the opportunity for you to make a mistake, and the same "5 point material advantage" of an extra rook is not so straightforward to convert to a win.

***So reduce the complexity***. Trade everything down until you have a rook and I have nothing. You indicate this is what you're trying to do, but that your trades are 'refused'. You will need to become better at 'forcing' trades. If you fork my knight and king with your knight, and your knight is protected, you have forced me to take your knight. Simply moving your knight in view of mine to 'tempt' me to take it requires me to choose to do so - as you rise in your chess level, your opponents will more often have their own plans, and you should never rely on someone 'being bad enough that they will play the way I want', always try to play in a way that doesn't require mistakes on the part of your opponent.

***And reduce the asymmetry***. Imagine you have a rook and 2 pawns, and I have a rook. Because we both have the same major piece, I can't attack your rook in a way that your rook can't attack back. Tactics might be possible on my part (skewering your king with your rook behind, as an example), but mostly your position is similar (but better) than mine. Asymmetry creates complexity that allows tactics to develop. Imagine instead I have a bishop and 2 pawns, and you have a rook and 2 pawns. From a material standpoint, this is still you being 'two pawns-worth of material' ahead, but now my bishop can attack your rook in a way that you can't immediately attack back, and my bishop also defends my pawns differently - it can become part of the pawn chain if needed, etc. Asymmetry naturally creates complexity, which creates the opportunity for me to prepare tactics, and also makes it easier for you to overlook something on the board.

**So your goal when it looks like you have enough material advantage to convert to a win** (as mentioned in other answers, the way to know this is to practice your endgames - for example are you confident in your ability to checkmate with a bishop and knight only?) would be as the mid-game winds down, to:

(1) Play defensively. Keep your pieces connected and close to eachother. Being aggressive can be risky, and you no longer need risk to win, you need simplicity. Don't overlook your opponent's threats, deal with them, even if it seems slower than a 'near checkmate' that you can't quite calculate but you think is probably there. Keep in mind that for a sub ~1600 rated player, the most immediate improvement to your play will likely be just to not 'drop' / 'hang' pieces. Simply by defending all your pieces, you will be doing something that your opponents are not always doing.

(2) Simplify. Force trades of material. Reduce asymmetry.

(3) Watch for potential pawn breaks, on your side and the opponents. 2 connected pawns on the 6th rank are worth about as much as a rook, so don't ignore the threat of promotion, even if you feel you have a material advantage.

(4) Keep your opponent's king "out of the game", by pushing it into a corner, especially preventing it from approaching your opponent's connected pawns. A king next to 2 pawns on the 6th rank is quite frightening indeed.

(5) *When safe* bring your own king into the game. As the material on the board simplifies, the relative power of a king increases, especially if there are no queens on the board, and even more so if there are no rooks on the board. If you're '2 points of material' ahead, but your opponent uses their king and you don't use yours, you will be unlikely to convert to a win.

(6) Checkmate using simple principles once the dust has settled. Really learn your endgames so that you are confident in all simplistic checkmates (especially with a single rook, and a single pawn - sometimes a single pawn is winning, sometimes it is a draw, you absolutely must learn how to win with a single pawn, because that's how a 1 point material advantage converts to a win).
> 11 votes

# Answer
My apologies in advance for the length of the answer. Additionally, I understand that the answer isn't responding directly to the question. Some parts of the answer are much more specific than what was asked in the question, and I've written analysis about a particular position from the game, even though the question specifically asks not to. The analysis is also probably complex enough that it would be hard to do in a rapid game. In my defense, I fully believe that the answer is the most helpful I can give. The game in the original post is quite interesting, and there are a number of complicated positions in the game, so a simple analysis won't cut it. Further, there just isn't enough good, specific information out there on the subject of playing with a material advantage--I felt the necessity to give something.

I will put a summary of my post here, though: **treat the material advantage as one of many positional aspects that guide you**.

---

Firstly, congratulations on playing a very good game (especially for a fairly new player) and then accurately identifying what areas could have been improved--that's a wonderful skill to have. As for your question, my experience working with relatively new players has made me quite skeptical that giving the "standard" advice for playing in winning positions is helpful. Just to be clear, the "standard" advice is completely correct, and a quick summary of it is:

* trade pieces and simplify
* attack the king instead of playing passively
* watch out for counterplay

Why am I skeptical that these guidelines are helpful? First, the advice is contradictory (trading defeats the purpose of playing for an attack, and attacking and defending against counterplay are hard to reconcile). However, the more important reason is that the real problem for the majority of players is that they find it difficult to play without clear positional advantages. (The reason that this is confused for not knowing how to play with a material advantage is because positional advantages won't be given up for nothing--usually, this happens after a tactical sequence that wins material.) For instance, consider the position just after you win the Exchange:

```
[White "NN"]
[Black "Matt"]
[FEN "r4rk1/2pp1ppp/p4nq1/1p2P3/1P6/P1B2P1P/BQ4P1/5RK1 b - - 0 22"]

```

What can we say about the position?

* Black is up an Exchange and a pawn
* White has a strong bishop pair and has a clear plan of advancing the kingside pawns (that is, the e-pawn and f-pawn)
* Black's queen might be vulnerable, the rooks lack good files, the knight has no outpost, and Black has no central presence; it's difficult to find a way to put the pieces on good squares

In short, White has serious compensation for the material. Black is definitely better, but I would not call the position "won." You did play a bit passively from this position, but passivity is usually a problem with moves, and not with thought process. There are players that just habitually play passively, but I'd definitely need to see more of your games to judge that, and judging from your play earlier in the game, I don't think you do. From moves 9 to 15, for instance, you play a series of positionally strong active moves designed to pressure the kingside and then the e4 pawn.

It seems to me that the problem isn't with activity or passivity, but rather that in the diagram position above, it's difficult to come up with a good positional plan. In the early middlegame, being able to "feel" good squares for your pieces helped you come up with good moves like ...Qh4 and ...Bd4, but it's hard to know where to put your pieces in positions like the one above. Thus, you made a few moves without a plan (like moving your queen along the 6th rank).

How can we improve our play in these positions? The basic skill that helps us here is learning how to *make positional advantages appear*. I'm aware that you're not looking for specific advice on how to play this position, but it's quite difficult to teach this sort of thing without a specific example, so I'll just write down my thought process. The generally applicable idea is that **you need to synthesize your calculations with general positional knowledge, just like in any other chess position**. This is where the "standard" advice I mentioned at the beginning becomes relevant: it's part of your positional knowledge of positions where one side has a material advantage. In your particular position, the emphasis should be on stopping the opponent from gaining counterplay, since that's what he's about to do.

The particular "sticking point" that's difficult for a lot of players to learn is that **you need to make certain features appear in the position, instead of just exploiting them when they do**. How do we do this? Let's look at a sample thought process:

* Obviously, the first priority is finding a good square for the knight. The only two safe squares are e8 and h5, and neither of them are long-term homes for the knight--we need to make one! Looking ahead a bit, I see three ideas: ...Nh5-g3-f5, ...Ne8 followed by ...c6 and ...Nc7-d5, and ...Ne8 followed by ...d6, hoping for exd6, and ...Nxd6-c4. Each of these has its drawbacks: ...Nf5 can be pushed out with g4 or pinned with Bb1, the ...c6 plan looks a bit artificial (read: dumb), and it seems hard to force him to play exd6.
* The rooks need open files. We have to make them! Some ways to open files in this position are ...d6, ...f6, and ...a5.

Note how none of these observations rely on the fact that you're up material! The next step is to start calculating. I'd start with ...Nh5, because if it works it will effectively freeze his kingside attack, and if White has no counterplay Black will eventually win. (This is where we use the fact that you're up material--part of the "standard" advice is that limiting counterplay is good when you're up material.) My two main worries were that the knight won't be able to stay on f5 because of g4 and Bb1. Do these work?

```
[Event "Rated Rapid game"]
[Site "?"]
[Date "2020.12.13"]
[Round "?"]
[White "NN"]
[Black "Matt"]
[Result "0-1"]
[FEN ""]
[StartFlipped "1"]
[UTCDate "2020.12.13"]
[UTCTime "08:02:31"]
[WhiteElo "1655"]
[BlackElo "1645"]
[WhiteRatingDiff "-6"]
[BlackRatingDiff "+10"]
[Variant "Standard"]
[TimeControl "600+5"]
[ECO "C48"]
[Opening "Four Knights Game: Spanish Variation, Classical Variation"]
[Termination "Time forfeit"]

1. e4 e5 2. Nf3 Nc6 3. Nc3 Nf6 4. Bb5 Bc5 5. O-O a6 6. Ba4 b5 7. Bb3 O-O 8. a3 Bb7 9. Re1 Ng4 10. Rf1 Nd4
11. Ba2 Nxf3+ 12. Qxf3 Qh4 13. h3 Nf6 14. b4 Bd4 15. Bb2 Bxe4 16. Qe2 Bxc3 17. Bxc3 Qg5 18. f3 Bxc2 19. d4 Qg6 20. dxe5 Bd3
21. Qb2 Bxf1 22. Rxf1 Nh5! 23. f4 Ng3 24. Bb1! {This is tricky. We have to move the queen, and
this complicates the ...Nf5 idea.} (24. Rf3 Nf5 25. Kh1 (25. g4? h5! 26. g5 d6 {
I stopped calculating here. The knight is fixed on f5, and the center will be
opened for the rooks.}) 25... h5! {I stopped calculating here, because White
won't be able to force g4. The next moves will be ...Rad8, ...d6, ...Rfe8 in
some order, opening files for the rooks.}) 24... Qc6! {This is probably the
most difficult move to see. Having realized that ...Nf5 probably isn't going
to happen, let's try putting the knight on e4. It turns out that we're just in
time to make this work.} (24... Qe6?! 25. Rf3 Nf5 26. Qf2! {The idea is to play
g4 without worrying about ...Nh4. I stopped calculating here because I can't
stop g4 and White's pawns look very strong. My computer says this position is
good for Black, but I wouldn't like to play it.}) (24... Qh5?? 25. Rf3 Nf5 26. g4
{I lose the knight.}) 25. Rf3 Ne4 26. Bxe4 (26. Qc2 f5! {Now either my knight gets a permanent outpost or White is forced to open
files for the rook.} 27. exf6 Nxf6 28. Bxf6 Qxc2 {I stopped calculating here.
White can't force a capture on h7, so I have nothing to worry about.}) 26...
Qxe4 {I made a piece trade (more "standard" knowledge) and now White's attack
looks weak.} 27. e6 f6 28. exd7 Rad8 {I stopped calculating here, since I will
win the pawn and there is no danger to my position.} *

```

This is not to say that my analysis is perfect--the computer objects to various things I've said here, the most glaring of which is that it's actually quite tricky to deal with 26. Bd4. The only purpose of the answer is to give an example of a human thought process in a very complicated position with material advantage, and to emphasize that the material advantage doesn't dominate the analysis--it is just blended in with the other positional features.
> 3 votes

---
Tags: beginner, psychology, middlegame
---


title: Find color of the pieces

text:
# Question
Title: Find color of the pieces
Given the following position, what colour are the pieces and what was the last move played?

```
[FEN "B1KRN3/PP6/2QK1R2/8/8/8/8/8 w - - 0 1"]

```

# Answer
> 8 votes
The difficult part of this puzzle is the realization that the pawn on b7 can actually be black. When this is established, the rest of the puzzle can be figured out without too much difficulty. Thus, if we assume that the pawn on b7 is black, what does this entail for the other pieces? Well:

* The bishop on a8 must be white, since it must've gotten there by means of pawn promotion. This further implies that the path to a8 must've been cleared for a white pawn at some point. Hence, the pawn on a7 must be white as well.
* Next, we realize that the rook on d8 and the queen on c6 must be of the same color (otherwise both kings would be in check). Moreover, these must be of the color opposing that of the king on c8; otherwise the king on d6 would be in check by the queen and the rook, which cannot be the result of a legal move on the previous turn. This, in turn, proves that the king on d6 is of the same color as all of the heavy pieces and the knight, since it couldn't possibly be in check.
* Finally, we determine the color of the king on c8. If it were white, then the rooks, and queen must be black by the previous point. But there is no legal move on the previous turn that black could've made to achieve this. So the king has to be black, which leads us to the realization that the last move played must've been cxd8=R, since the move must've been a discovered check (Note that this implies that the pawn on b7 must indeed be black, since the arguments concerning the heavy pieces are not dependent on the color of this pawn).

So, this must be the solution (the knight is indeed the only possible piece that could be on d8 in the initial position, as pointed out by James Martin in the comments):

```
[FEN "B1knN3/PpP5/2QK1R2/8/8/8/8/8 w - - 0 1"]

1.cxd8=R

```

---
Tags: problems, retrograde-analysis
---


title: How do you use Sesse?

text:
# Question
Title: How do you use Sesse?
How can I set up a position on Sesse? I've been trying to find a way to set up a position on the blank chessboard for half an hour unsuccessfully. How do you do it?

# Answer
> 3 votes
It doesn't work because there's a bug. If you open the console (F12 → Console) you'll see some errors. It seems that an essential file is missing from the server. Until it is fixed, you should probably use another analysis board.

# Answer
> 4 votes
Sesse isn't meant to be used by random viewers like you and me. It's someone's private server with which he follows top level games sometimes (mostly Carlsen's). And if the analysis is on the web anyway, then why not share it with us.

---
Tags: engines, websites
---


title: Brainteaser puzzle

text:
# Question
Title: Brainteaser puzzle
So... initial position is

```
[FEN "7k/8/6KB/8/p7/8/Q7/8 w - - 0 1"]

```

Now... Neither white's king nor queen has moved in the previous five moves. In addition, no pieces have been captured by either side. What was the last move? Also, where the piece came from here?

Since the black's king can't move it's very tempting to say that black's last move was a pawn move or white's last move was a bishop move. The tricky part is the mention of 5 moves. Black's pawn can only do 3 moves from starting position, and since white's queen and the king didn't move, black's king is stuck.

# Answer
As the Black pawn can only have made three moves, the Black king must have made two moves. As the entrance to h8 is blocked, the White queen's line of attack must have been blocked at some point. The White king has not moved, and the Black pawn cannot block that line, so it must have been the White bishop. But **the White bishop** is a dark-square bishop, and cannot block the White queen along a light-colored diagonal, so it **must come from a pawn promotion**. The question "Where does the piece come from?" in the OP is a hint.

Here is a solution where the last move was a Black move. I think the problem cannot be solved if the last move was a White move:

```
[FEN "5k2/p7/6K1/3P4/8/8/Q7/8 b - - 0 1"]
[StartFlipped "0"]

1... Kg8 2. d6+ Kh8 3. d7 a6 4. d8=B a5 5. Bg5 a4 6. Bh6

```
> 7 votes

---
Tags: problems, retrograde-analysis
---


# Question
Title: What did Benjamin Franklin mean in this quote?
I was reading thenarticle at http://www.chess.com/forum/view/general/benjamin-franklin-on-the-morals-of-chess, and in the last paragraph, Ben Franklin says "Snatch not eagerly at every advantage offered by his unskilfulness or inattention; but point out to him kindly, that by such a move he places or leaves a piece in danger and unsupported; that by another he will put his king in a perilous situation, etc."

But he also says "If you touch a piece, you must move it somewhere; if you set it down, you must let it stand." So if my opponent moves their queen to a spot where I could capture her, what would be the advantage of pointing out that his queen is in danger, since he cannot move his queen back to a safe spot (because once they set it down, and therefore must let it stand)?

# Answer
You hold yourself to a higher standard than your opponent, for politeness' sake.

So you let *him* play an alternative move after you kindly point out that it was perhaps not the best available, but *you* are acquiring a habit of caution by adhering strictly to the laws of the game for your own moves.

The point is to be moral, polite and extremely smug at the same time.
> 12 votes

# Answer
That sentence is taken out of context. I copy here the text of the full paragraph, which answers your question:

> If the game is not to be played rigorously, according to the rules above mentioned, then moderate your desire of victory over your adversary, and be pleased with one over yourself. Snatch not eagerly at every advantage offered by his unskilfulness or inattention; but point out to him kindly that by such a move he places or leaves a piece in danger and unsupported; that by another he will put his king in a dangerous situation, &c. By this generous civility (so opposite to the unfairness above forbidden) you may indeed happen to lose the game to your opponent, but you will win what is better, his esteem, his respect, and his affection; together with the silent approbation and good will of impartial spectators.

In fact Franklin, distinguishes two ways of playing the game, with strict observance to the laws of chess or not observing them exactly. Whether you play one way or the other should be agreed by both players, and both players should be treated in the same way.

In the first case, with strict observation of the rules, a piece touched should be moved, a piece moved should stand. And you shouldn't point out the opponent's errors.

However, in the second case, where you play a more informal game, he recommends pointing out the other player's errors out of politeness and good will. This might be applicable when playing against a beginner player who is still learning the game, or a much lower rated one, during an informal game. But also when studying a position/opening/endgame with a colleague.
> 6 votes

---
Tags: history, psychology, queens, chessboards, advantage
---


# Question
Title: Is it possible to reach King vs King by moving each piece at most twice?
I'm interested in short games that reach a King vs King endgame. Sam Lloyd reached King vs King after only 17 moves. This has since been improved to 16.5 moves. (See this and that.) One can show that this is optimal. In these games, almost all captures are performed by queens and rooks, but I'd like to see a massacre with more diverse captures.

**Question 1:** Is it possible to reach a King vs King endgame by moving each piece at most twice?

Notice that you can't get away with moving each piece at most once, since this would give King vs King in only 16 moves.

**Question 2:** Assuming such games exist, what's the shortest game?

Please post a game and report the number of moves.

# Answer
> 10 votes
**Answer 1**: Yes, this is possible. Here is an example game in 27 moves:

```
[FEN ""]

1. a4 a5 2. b4 b5 3. bxa5 bxa4 4. Rxa4 Nc6 5. g4 Nxa5 6. Rxa5 Rxa5 7. h4 g5 8. hxg5 h5 9. gxh5 d5 10. c4 Nf6 11. cxd5 Nxd5 12. e4 Bb7 13. exd5 Bxd5 14. Nc3 e6 15. Nxd5 exd5 16. Bg2 c5 17. Bxd5 Rxh5 18. d4 Rxg5 19. dxc5 Bxc5 20. f4 Bxg1 21. Rxg1 f6 22. fxg5 fxg5 23. Rxg5 Qxd5 24. Ke2 Qxd1+ 25. Kxd1 Rxg5 26. Bxg5 Kd7 27. Bd8 Kxd8

```

You can even insert some moves that slow the game down so that *every piece moves **exactly** twice*. Sadly, this is the opposite of your second question.

```
[FEN ""]

1. a3 a6 2. a4 a5 3. b4 b5 4. bxa5 bxa4 5. Rxa4 Nc6 6. g4 Nxa5 7. Rxa5 Rxa5 8. h4 g6 9. Nh3 g5 10. hxg5 h6 11. Ng1 h5 12. gxh5 d6 13. c4 d5 14. Qc2 Nf6 15. cxd5 Nxd5 16. e4 Bb7 17. exd5 Bxd5 18. Nc3 e6 19. Nxd5 exd5 20. Bg2 c6 21. Qd1 c5 22. Bxd5 Rxh5 23. d4 Rxg5 24. dxc5 Bxc5 25. f4 Bxg1 26. Rxg1 f6 27. fxg5 fxg5 28. Rxg5 Qxd5 29. Ke2 Qxd1+ 30. Kxd1 Rxg5 31. Bxg5 Kd7 32. Bd8 Kxd8

```

---
Tags: theory, problems, records, mathematics, kings
---


# Question
Title: On an infinite board, which pieces are needed to checkmate?
Most of the winnable endgames require cornering the opposing king to checkmate, often using zugzwang. However, if you have an infinite board (infinite in every direction), you won't be able to corner the opposing king as easily, as they will be able to retreat unless there is a threat behind them. For example, queen vs king will be a draw in this scenario, as the king and queen will never cover all escape routes. I also believe that two rooks will be unable to deliver mate, as you cannot force opposition. However, queen and rook will be able to checkmate, by using the queen to create a "corner" and checkmating using rook and king. In general, if a combination mates in a regular board, that combination plus a queen will be able to mate here; but I'm looking for more interesting combinations.

So, which piece combinations will be able to mate in this scenario?

# Answer
Here are some mates I found:

1. Queen and rook (limit the black king until the white arrives to help)

```
[Title "KQR vs k mate"]
[FEN "1R6/5k2/8/8/8/8/6Q1/K7 w - - 0 1"]

1. Qg8+ Ke7 2. Rd8 Kf6 3. Re8 Kf5 4. Kb2 Kf4
5. Qg2 Kf5 6. Kc3 Kf6 7. Kd4 Kf7 8. Qg8+ Kf6
9. Ke3 Kf5 10. Kf3 Kf6 11. Re6+ Kf5 12. Qg6#

```
2. Queen and pawn (not sure if the position can be reached with optimal play)

```
[FEN "8/8/4Q3/3Pk3/8/4K3/8/8 w - - 0 1"]

```
3. Queen and bishop (again, limit the king with the queen and the bishop, so the attacking king finds the time to approach)

```
[Title "KQB vs k mate"]
[FEN "Q7/2k5/8/8/B7/8/8/7K w - - 0 1"]

1. Kg2 Kb6 2. Kf3 Kc5 3. Qb7 Kc4 4. Ke3 Kc5
5. Ke4 Kd6 6. Qd7+ Kc5 7. Qd4#

```
4. Queen and knight (limit the black king with the queen and the knight as much as possible)

```
[Title "KQN vs k mate"]
[FEN "Q7/2k5/8/8/8/1N6/8/7K w - - 0 1"]

1. Kg2 Kd7 2. Kf3 Ke7 3. Ke4 Kf6 4. Qg8 Ke7
5. Ke5 Kd7 6. Kd5 Ke7 7. Nc5 Kf6 8. Ne4+ Ke7
9. Ke5 Kd7 10. Nd6 Kc6 11. Qb8 Kc5 12. Qb5#

```
5. Two rooks (Noam's answer mentions how the mate can be forced)

```
[FEN "8/8/R7/1R2k3/8/4K3/8/8 w - - 0 1"]

```
> 15 votes

# Answer
In fact K+R+R can force checkmate against K on an open board.

First move both Rooks away from the King and to different rows and columns.

Then check the King with one Rook, say on a row. Whichever side the King goes, move the other Rook to limit it to a single row.

Now the Rooks, moving only horizontally, can limit the defending King to just four squares on that row, with enough spare moves for the attacking King to approach:

```
[Title "RR keep K boxed in"]
[FEN "R7/5k2/2R5/8/8/8/8/K7 w - - 0 0"]

1. Rh8 Kg7 2. Rch6 Kf7 3. Kb2 Ke7 4. Rc8 Kd7 5. Rhc6 Ke7 6. Kc3 Kf7 7. Rh8

```

Once the King has joined the fray, mate can soon follow. For example:

```
[Title "KRR mate K on infinite board"]
[FEN "7R/5k2/2R5/8/3K4/8/8/8 w - - 0 0"]

1. Ke5 Kg7 (1... Ke7 2. Rc7#) 2. Rch6 Kf7 3. Kd6 Kg7 4. Kd5 Kf7
5. Ke5 Kg7 (5... Ke7 6. R6h7#) 6. Kf5 Kf7 7. R6h7#

```
> 26 votes

# Answer
An *infinite* number of knights would be insufficient to force checkmate, assuming the enemy king starts some distance away and not surrounded. The knights are too slow and not enough of them can chase an enemy king that simply runs away.

A rook and two bishops, on the other hand, could force checkmate. It's rather easy to force a position like this:

```
[FEN "3BB3/8/4k3/R7/8/8/8/4K3 w - - 0 1"]

```

The Black king can only shuffle between two squares while the White king gets into position on d4 or e4 to set up Ra6#.

Four bishops could also force a checkmate:

```
[FEN "3BB3/8/4k3/8/3BB3/3K4/8/8 w - - 0 1"]

1. Bc5 Ke5 2. Bd7 Kf4 3. Bd6#

```

I'm guessing that three bishops and a knight, or two bishops and two knights, could also force checkmate. The bishop pair is very effective at corralling the enemy king.
> 13 votes

---
Tags: checkmate, chess-variants
---


# Question
Title: Resources to study benchmark opening positions, or "ideal setups"
I noticed that strong players often discuss openings in the following terms: "this is an ideal setup in this opening", or "this play in opening X is bad because all you get is a worse version of opening Y". In other words, an extremely useful way to evaluate a position is to compare it to some benchmarks. However, when studying openings, it is often hard to pinpoint what are these "ideal setups" and why they are ideal. GMs will never allow each other to get a dream scenario, so studying their games does not help. Ditto for theoretical lines. So, I always feel that I'm studying shadows on a wall, while these platonic "ideal Ruy Lopez" or "ideal French" never appear explicitly.

What are some good ways/resources to fill these gaps? Is it useful to study games by *lesser players* who allowed this "ideal French" appear on the board and lost in an instructive way? Are there collections of such games? There are many collections of "miniatures" in which one side falls for a trap, and often a master is known solely for being defeated in this miniature. But what about collections of games where black loses on move 50, but was doomed by move 15 because they allowed white to put their pieces on all best squares and execute their dream plan? Or are there books that focus on this aspect?

# Answer
> 2 votes
I agree that in a well known opening Ideal positions may not be allowed by opponents, but this is not true when an opening is new and the strongest players are discovering the ideal (without the help of a computer)

When I was learning the King's Indian Defense I played through many games from the 1940's and 50's by Bronstein, Geller, Gligoric, Najdorf.

For Queen's Gambit, the 1910 - 1930 are good years to look at.

Also, learn the Tabiyas of your opening. Many good opening books have a page or chapter on the key positions to understand in that opening. This is part of what makes them good. I keep a document of the Tabiyas of all the openings I play with short notes on the plans for both sides in that position.

---
Tags: opening, learning
---


# Question
Title: Where does the black king stand in this specific position?
```
[FEN "7r/pppppKpP/6P1/8/8/8/n7/8 w - - 0 1"]

```

Assume that the following position was reached in a legal game of chess. In the last 5 moves, no pawn has moved and no pieces were captured. The Black king is invisible – on which square does it stand?

# Answer
The black king must be on c8.

The white king reached g8 through g6 and h7 before the white pawns arrived on g6-h7. A white knight took the Bc8 from b6; the black queen was also taken by a knight. The black king remained en e8, and the black rook on a8, until a few moves ago.

The last moves were for instance:

```
[Title "Invisible Black King solution"]
[FEN "r3k1K1/ppppp1pP/6P1/8/8/8/8/2n5 w q - 0 1"]

1. Kh8 Na2 2. Kg8 Nc1 3. Kh8 Na2 4. Kg8 O-O-O+
5. Kf7 Rh8

```
> 8 votes

# Answer
Evarglo's answer is correct, but doesn't give any reasoning for why lines that involve queen-side castling are the *only* viable ones.

The key to the puzzle is noticing that with the pawns in their current position, the White King can't approach it's current location from the White side of the board. Thus it must have just moved from the 8th row. Further the Black King is trapped on the 8th row too and, without castling, the Black Rook is trapped on *that side* of the 8th row.

This obviously causes problems: if those pawns have been in place for 5 turns, and no pieces have been taken then that means that white has only been moving his King ... and where has it been moving, if the black rook was covering that entire side of the 8th row?

One might think that there had been a black piece on f8/g8, allowing the White King to move around on the 9th row, but the blocking piece would have had to have been taken recently ( the Knight on a2 is too far away to have been 'helping').

The only conclusion left is that the Black Rook *wasn't* on this side of the Black King, until the last few turns. ... leading to the given solution.
> 3 votes

---
Tags: problems, retrograde-analysis
---


# Question
Title: I refused to sign the scoresheet but the arbiter signed with my initials. What should I do?
I refused to sign my scoresheet, as I was planning to lodge an appeal. Yet, the arbiter signed the scoresheet with my initials. I know I didn't lose my right to object. However, I'm afraid that my appeal will be denied because the claim that I didn't sign the scoresheet will be disputed.

What should I do and how can I prove otherwise?

# Answer
> 12 votes
* If the arbiter really signed with your signature, instead of his, then he just committed a crime (forgery of documents). He could have signed with his signature as proof that he confirmed the result of the game and everything on the scoresheet.
* If the arbiter really forged your signature, then as a first step you should lodge a complaint against the arbiter with the tournament organizer. Next, if necessary, do the same with the federation that organizes the tournament. Depending on how serious the matters are, the police may be involved, but most likely you can solve it peacefully.
* Obviously in parallel, you still put your initial claim about the game on appeals committee desk.

---
Tags: rules, tournament, scoresheet, arbiters
---


# Question
Title: Order of pieces in one-dimensional array
To store pieces inside an array of 64 squares (inside a one-dimensional chessboard), I would simply convert squares like:

* `0` is a8
* `1` is b8
* `2` is c8

...

* `63` is h1

This order would be natural for me, as we can then easily loop and display each square to represent the board on a document, having at the bottom the white perspective.

But looking at some documents on the computer chess, such as the 0x88 board representation, it seems that the standard way to order pieces in rather this:

* `0` is a1
* `1` is b1

...etc.

Do you think I should definitivly use this same ordering? Or would it make more sense to adopt the more natural order (`0` is a8)?

# Answer
> 7 votes
They're both equally natural, they just start at a different square. But that choice is arbitrary anyway. Printing to a terminal is one of the least critical things a chess engine does with a board, and looping can go in the other direction just as easily.

If you want to be able to easily copy algorithms or code from examples or other engines (the license of which allows you to do that), it can be helpful to use the same conventions as most people do. But that's completely up to you.

---
Tags: programming, chessboards
---


# Question
Title: How does his 3 step plan by Petrosian works?
```
[FEN "r6k/3q2bp/1p6/2pPp1p1/2P1QpP1/5P2/1P2R2P/2B3K1 w - - 0 1"]

```

Here Petrosian gives the following 3 step winning plan:

Stage 1: Tie down the black pieces to defense of the e pawn: 13.Bd2 Re8 14.Bc3 Qd6 15.Re1

Stage 2: Switch to the a file: 15..h6 Ra1 and then Ra7

Stage 3: Penetrate into the white squares.

Now what I don't understand is this: when he proceeds with stage 2 by bringing the rook to a file, isn't he removing one attacker of the e pawn? Now black's pieces will not be tied to the e pawn anymore. So, how is this plan any effective?

# Answer
> when he proceeds with stage 2 by bringing the rook to a file, isn't he removing one attacker of the e pawn? Now black's pieces will not be tied to the e pawn anymore. So, how is this plan any effective?

Currently black controls the a file with the rook on a8. The whole point of step 1. "tie down black pieces defending e pawn" is to force the a8 rook to give up the a file to defend the e pawn with Re8. Only when that is accomplished can white take over the a file with Ra1. The whole point of having a multi step is achieving the last step. The earlier steps are only necessary because without them the last step cannot be forced.
> 3 votes

---
Tags: analysis, strategy, middlegame
---


# Question
Title: Gambit openings for black recommendation?
I recently started to learn chess, but I play mid to advanced Chinese chess. So to get the most out of transferable skills, I would like to avoid positional/pawn play, but prefer aggressive openings to bring non-pawns into contact very early.

I tried a bit with King's Gambit and Smith-Morra for playing white. What are the aggressive (gambit?) defense lines for black against 1.e4 and 1.d4? Are there early gambits that are easy to reach but hard to decline, even if in theory white's better?

Thanks.

# Answer
> 10 votes
Two gambits that your opponents would likely play into a fair amount, and are defined by move two, are the Latvian Gambit (`1.e4 e5 2.Nf3 f5`, like a reversed King's Gambit) and the Albin Counter-gambit (`1.d4 d5 2.c4 e5`). Between the two, the Albin is considered more sound, and even sees top-level games from the likes of Morozevich and Nakamura. The Latvian is generally seen as much shakier. In any case, these two bring the fight to White without delay, and might be the sort of flavor you're looking for.

```
[White "Latvian"]
[Black "Gambit"]
[fen ""]

1.e4 e5 2.Nf3 f5

```

and

```
[White "Albin"]
[Black "Counter-Gambit"]
[fen ""]

1.d4 d5 2.c4 e5

```

# Answer
> 7 votes
I have a very good gambit for you, with black against 1. d4. it's called **Benko gambit**:

```
[White "Benko"]
[Black "Gambit"]
[fen ""]

1. d4 Nf6 2.c4 c5 3.d5 b5

```

It later gives you some ultra strong attack from the queen side, if white takes cxb5 your next move is a6 and then the opening branches out :)

# Answer
> 3 votes
The Traxler counterattack is one of the most aggresive openings for both sides:

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

1. e4 e5 2. Nf3 Nc6 3. Bc4 Nf6 4. Ng5 Bc5

```

Also the Stafford gambit is popular nowadays:

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

1. e4 e5 2. Nf3 Nf6 3. Nxe5 Nc6

```

---
Tags: opening, gambits, aggressive-play
---


title: Why Qxd5 instead of Rxd5?

text:
# Question
Title: Why Qxd5 instead of Rxd5?
This puzzle on chesstempo caught my eye. We play as Black:

```
[FEN "1r1r2k/p4pp/2q/2p1p2P/P1P1Pn/B3NP/4Q2P/R6K w - - 0 1"]

1. Nd5

```

The White queen is under attack, yet one shall not rush and capture it. The White may fork the Black king and queen and then fork two rooks:

```
[FEN "1r1r2k/p4pp/2q/2p1p2P/P1P1Pn/B3NP/4Q2P/R6K w - - 0 1"]

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

```

So, we lose a rook here. Therefore, we need to capture the knight. I took the knight with the rook:

```
[FEN "1r1r2k/p4pp/2q/2p1p2P/P1P1Pn/B3NP/4Q2P/R6K w - - 0 1"]

1. Nd5 Rxd5

```

Yet, chesstempo wanted me to capture it with the queen:

```
[FEN "1r1r2k/p4pp/2q/2p1p2P/P1P1Pn/B3NP/4Q2P/R6K w - - 0 1"]

1. Nd5 Qxd5
2. cxd5 Nxe2

```

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

# Answer
> 16 votes
After 1...Rxd5 2.cxd5, *both queens are attacked*. They either both get captured, or (if black moves his to safety) neither is. So black lost the exchange.

After 1...Qxd5 2.cxd5 Nxe2, white has lost a knight.

Cxd5 seems the better capture to me on general grounds (repairs white structure a bit, makes pawn c5 weaker) but that's far less important than the full rook difference between 1...Rxd5 and 1...Qxd5.

---
Tags: puzzles, zwischenzug, fork
---


# Question
Title: Is the Four Pawns Attack against the Alekhine opening promising for White?
The latest version of Stockfish 12 thinks that the Four Pawns Attack is the most promising variation for White against the Alekhine Defense `1.e4 Nf6`, But it evaluated the position resulting from the Four Pawns Attack vs the Kings Indian as close to zero. Is it really all that practical?

# Answer
> 2 votes
There's a concept in chess called the equilibrium. Basically, things start off more or less equal, and both sides try to upset the equilibrium in their favour (i.e., gain an advantage). If one side makes a mistake and upsets the equilibrium in their opponent's favour, then their opponent is "justified" in playing in some way to capitalize on this mistake. This often involves being aggressive and attacking. If it weren't for the mistake, the equilibrium would be maintained, causing such an attack to not work and be rebuked (assuming optimal play).

I don't know whether the Four Pawns Attack is the best line against the Alekhine, but at the very least it's one of the best. The reason it works is that White is justified in playing this way. Black has spent multiple tempi moving his knight around the board, mainly for the sake of provoking White's pawns forward. This upsets the equilibrium a bit in White's favour, giving him a free hand to be aggressive without getting punished.

Meanwhile for the KID, the opening is generally quite well regarded. Black develops quickly and is basically being no-nonsense in his approach; this ensures the equilibrium more or less gets maintained. Therefore, White isn't as justified in attacking so early on. He can certainly try with the Four Pawns, and while he's still equal Black has the resources to defend effectively.

Also, while it's true that the KID doesn't control the centre much on the first few moves, it is of those openings where Black can get away with this. So this doesn't drastically upset the equilibrium in White's favour.

# Answer
> 1 votes
As far as I know, the short answer is no. I am no expert on the theoretical part and I will not go into it because it will require more research. What I do assume is that any player who plays the Alekhine Defense with the Black pieces has studied the Four Pawns Attack. Thus, it makes more sense to me from a human and psychological point of view to choose something less well studied. One line that I used to play goes like this.

```
[Title "A line against the Alekhine Defense"]
[FEN "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"]
1.e4 Nf6 2.e5 Nd5 3.d4 d6 4.Bc4

```

Perhaps you can find some games and see if the positions seem interesting. In general, I would say that getting someone out of their comfort zone and out of their known positions is more important than objective evaluations of positions. I hope this helps.

---
Tags: opening, theory, attack, aggressive-play
---


# Question
Title: Is there an aggresive opening for black if white does not accept the Traxler's counterattack?
I want to play sharp, complicated Traxler games in bullet. To do this, I *must* play the Two Knights Defence. The problem is that rarely people go for the Fried Liver, and usually I play the Four Knights Italian or the Giuoco Piano opening.

```
[FEN "r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4"]

1. Nc3

```

or

```
[FEN "r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4"]

1. c3

```

or

```
[FEN "r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4"]

1. d3

```

Is there a gambit or an aggressive opening/response that could complicate the game from this position into an attacking aggressive battle for **Black**?

**NOTE:** I don't expect the opening to be any good

# Answer
> 3 votes
The Traxler counter-attack starts if White plays Ng5 in this position.

```
[FEN "r1bqkb1r/pppp1ppp/2n2n2/4p3/2B1P3/5N2/PPPP1PPP/RNBQK2R w KQkq - 4 4"]

1. Ng5

```

Without Ng5, there is no Traxler counter-attack.

I think that 1.e4 e5 is not the best way of preparing an attacking and aggressive battle with Black. That is why I play 1.e4 c5 and go for the Sicilian Najdorf variation. I think that asymmetry is a good way of seeking imbalance and dynamic play. While symmetry is more likely to lead to less dynamic positions. Thus, 1.e4 c5 and 1.d4 f5 are approaches to seek more dynamic play, in most extreme cases, by castling on opposite sides and launching pawn storms. Your opening choice leaves White with the option of accepting with Ng5 or declining with a different move. If you want to ensure dynamic play, I think it is better to look for opening systems where you have more control of where the game goes so to speak. I hope this helps.

# Answer
> 3 votes
In response to:

* 4.c3. This outright loses a pawn to 4...Nxe4. I have a hard time believing White will play this often.
* 4.Nc3. This move is tame, effectively accepting a symmetrical position with minimal advantage if Black plays 4...Bc5. Black does not have to acquiesce and could play 4...Nxe4 5. Nxe4 d5 giving Black easy development and a comfortable game. I get that it's not what exactly you are looking for, but with open lines in the center you should be able to find tactical lines.
* That leaves 4.d3, against which you can play 4...d5. This move forces open the center before either side has completed development, making it inherently provocative, but it again allows tactical ideas to surface.

You could also try a different opening in the Sicilian as suggested by Rauan Sagit, but the Two Knights is plenty provocative itself.

---
Tags: gambits, attack, aggressive-play, fried-liver-attack, traxler-counter-attack
---


title: Why is castling here a mistake?

text:
# Question
Title: Why is castling here a mistake?
I am back at chess after two years and am enjoying it a lot. I was playing and this happened after I checked a report at chess.com:

I have googled the importance of when to castle the king. Here I know castling isn't the best move, but why is it a mistake?

# Answer
The engine is giving you an answer. Black plays **... Na5** followed by **... Nc4** which prevents White from bringing pieces over to the queenside, because of the White doubled pawns on c2 and c3. Which means the White king is now stranded by itself on the queenside.

Black is going to play **... c5** and bring the queen out to a5 or b6. On a5 it threatens **... Qxa3** with mate to follow. On b6 it's threatening **... Qb2** with mate.

What queenside castling has done is to put the White king into the line of fire, in a way that Black has at least two pieces converging to attack, and White has none. Even, if by miracle, White gets some pieces over to the a- and b-files, Black's other pieces will enter the fray much quicker and in much larger numbers: The a8 rook by pushing the a-pawn, the c8-bishop via d7.

The chess engine reckons White is going to lose at least a rook to stave off this attack (this is simply the difference between the position evaluation after queenside castling -6.27 versus the best move Nf3 which is evaluated to -1.74).

In logical terms, you castled into an attack on the queenside. With the centre as constricted as it is, your king was fairly safe remaining in the centre uncastled for the time being. You needed to develop the Knight to f3, and the bishop to e2, and take it from there.
> 12 votes

---
Tags: castling
---


# Question
Title: Is there any obvious disadvantage of not castling in a game?
The opponent has the option of castling but can I still play a solid game without castling either side? I won some games in bullet time controls but only because position was too complex and opponent lost on time. Please answer with respect to different time controls. (my rating: ~1700 on lichess)

# Answer
> 11 votes
The purpose of castling is to make the king safe. How important castling is in any particular game depends almost entirely on how safe the king is in the center. If the center is completely open (say all four central pawns have been exchanged) and many pieces are still on the board then it is very dangerous to leave the king in the center. If the center is completely closed, however, then the king may be much safer in the center.

On the other hand there are openings (Berlin Defence to the Ruy Lopez for example) where the queens come off very quickly and one side having an uncastled king is fine and confers no disadvantage.

Time controls have nothing to do with this. Having an unsafe king while your opponent's king is safe just makes your opponent's game much easier regardless of time control. You could even argue that the shorter the time control the less time you have to make plans so the easier it is for the player with the safe king because all they have to do is attack the opponent's unsafe king.

# Answer
> 2 votes
There are openings where you can keep your King on its initial square for more moves. I personally prefer to castle relatively quickly. Castling has a good psychological advantage of taking care of King safety before planning the next phase of the game.

A game in my mind goes something like this.

1. initial development to control the center and prepare castling
2. castle the King
3. continue taking control of the center
4. launch an attack or counter-attack

If I keep my King in its initial square, I have to spend extra time on considering its safety. With a castled King, I have clear ways of defending it from an attack, because I know the usual patterns of attack and defense depending on which side I castled. If my opponent waits with castling, I start disrupting their structure on the side where I do not want them to castle.

One situation where I delay castling is to see where my opponent castles, in case I want to either avoid or ensure a castling on opposite sides. Positions where two players castled on opposite sides are very sharp and have a specific character. Pawn storms will be launched on both sides and the position will get complicated, dynamic and require a lot of calculation.

Those are some of my thoughts on the topic. I hope it helps you to decide what to do with your King. I think you can use the same principles across all time controls, just as Brian pointed out. I hope my answer added something useful. Let me know if you have any comments.

# Answer
> 0 votes
You want to know if castling is absolutely necessary. It depends upon the position. The main purposes of castling are to safeguard the king and connect the rooks. In general, with an intact pawn structure the king is normally safer in the corner after castling where the opponent's attacking lines are fewer. In the center, it can be attacked from eiher side. But if the position is blocked as it can become in a closed game, there may be no hurry to castle. If a lot of pieces get exchanged off, it may then be desirable to have the king nearer the center for the endgame. Which side your opponent has castled on can also be a factor, since you don't want to castle into a potential pawn storm on opposite side castling. So there's really no hard and fast answer to your question, and it depends largely upon the circumstances. I might add that I play a lot of games against the computer when it doesn't castle, and I find it much easier to attack the king then, with an impressive record of resulting wins.

---
Tags: strategy, theory, castling
---


title: Why was this stalemate?

text:
# Question
Title: Why was this stalemate?
I'm new to chess and I don't have much knowledge. But I was playing a game as Black, and I was up by a lot of material and played Nxc4 to capture White's last bishop. The game ended in a stalemate, even though the king was trapped, I think.

```
[FEN "2qk1b2/4n2p/1n3p2/3p4/b1BK4/5r2/7r/8 b - - 0 1"]

1... Nxc4

```

Can anyone explain to me please why this happened and why I didn't win?

# Answer
# Stalemate

> **Stalemate** is a situation in the game of chess where the player whose turn it is to move is not in check but has no legal move. ... In popular usage, the word stalemate refers to a conflict that has reached an impasse, and in which resolution or further action seems highly difficult or unlikely.

In the above position, your opponent had no legal moves but was not on check hence stalement. The objective of chess is to;

> The object of the game is to checkmate the opponent; this occurs when the opponent's king is in check, and there is no legal way to remove it from attack. It is never legal for a player to make a move that puts or leaves the player's own king in check.

So if this is not achieved there is no winner unlike in checkers where you can win if your opponent has no legal move
> 10 votes

# Answer
According to the rules of chess, a stlemate (draw) occurs when the player whose turn it is to move has no legal move. That's the situation here where upon your capturing the bishop, the White king cannot move without placing itself in check, which is illegal. Accordingly, the result is a draw by stalemate.
> 0 votes

---
Tags: checkmate, stalemate, kings
---


title: A mate in two problem

text:
# Question
Title: A mate in two problem
```
[FEN "8/8/4R3/8/2kBn3/K2pQ3/8/8 w - - 0 1"]

1. Re5?

```

With White to move, here is a mate in two problem that I couldn't figure out. My opinion is that the first move is 1. Re5, but Black still has a variety of moves. Does anyone have better ideas on how to solve it?

# Answer
> 6 votes
With the rook on e6, Bb6 is mate in two. For instance

1. Bb6 d2 2. Qb3 mate or 1. ... N any 2. Qc5 mate or 1. ... Kc3 2. Qc1 or 1. ... Kc5 2. Qxd3 or 1. ... Ke4 2. Qxe4

# Answer
> 1 votes
I think it is useful in these sorts of problems to categorize moves. You say that Re5 looks promising, but that there are too many moves for black afterwards. I would work through this as follows:

What's good about Re5? It prevents the opponent's king from moving, shrinking the possibilities we need to consider. The threat is 2. Rc5#, but this is prevented by black's knight. If knight moves, 2.Rc5# will be possible because there are no checks. If pawn moves Rc5# remains impossible and no other mate presents itself.

Note that I don't need to consider where the knight is moving *to*. Since we know our threat after Re5 all we have to consider are moves that prevent that threat from working. d2 is such a move, and tells us that Re5 doesn't work.

To find the correct solution, we need to find a different solution to 1... kb5 or kd5. Blocking with the rook of queen like you've proposed doesn't work, so we have to instead look for situations where those moves are mate in 1. This leads us to realize our bishop being in the way is a serious problem, which motivates 1. Bb6, which is indeed correct.

---
Tags: checkmate, problems
---


title: Why does White play Qxd4?

text:
# Question
Title: Why does White play Qxd4?
This puzzle on chesstempo caught my eye. We play as Black:

```
[FEN "r2qk2r/1p1bppbp/p1np2p/4P2n/Q8/2N2N1P/PPP2PPB/R3KB1R w - - 0 1"]

1. exd6

```

My solution is: if we play 1... Nb..., a discovered attack by the bishop on a White queen takes place. Therefore, we shall use this knight wisely. The interesting thing we may do is threatening a fork on the king and on the rook (2... Nc2+) playing Nbd4. It is the right move:

```
[FEN "r2qk2r/1p1bppbp/p1np2p/4P2n/Q8/2N2N1P/PPP2PPB/R3KB1R w - - 0 1"]

1. exd6 Nbd4

```

I wanted to make the White queen move so it would be no longer defending the c2, making the fork possible (that would something like 2. Qc4):

```
[FEN "r2qk2r/1p1bppbp/p1np2p/4P2n/Q8/2N2N1P/PPP2PPB/R3KB1R w - - 0 1"]

1. exd6 Nbd4
2. Qc4 Nc2+
3. Kd2 Na1

```

And yet, the White plays 2. Qxd4 and gives Black the queen. Then White captures the bishop:

```
[FEN "r2qk2r/1p1bppbp/p1np2p/4P2n/Q8/2N2N1P/PPP2PPB/R3KB1R w - - 0 1"]

1. exd6 Nbd4
2. Qxd4 Bxd4
3. Nxd4

```

The only reason as to why White would answer this way I found afterwards is White not losing a piece (they get to capture the knight, which couldn't have been captured after the fork) and losing the same material (-Queen + Bishop = -8 + 3 = -5 = -Rook). Yet this seems a bit weak. If I were White, I would have played the other way. Yet, I am no old hand in chess, so there is no good reason to trust my gut. What is more important here: not to lose the queen, or not to lose the pieces? Anyway, why does White play 2. Qxd4?

# Answer
1. exd6 is bad because it opens up the bishop on g7. This would happen anyways, but it just made Black's job easier. It also completely opens the centre, which is not a good thing to do, especially when the king hasn't castled. Finally, it ignored the bishop that is indirectly threatening the Queen.

The correct response is 1... Nd4 which enables the Bishop to (directly threaten the queen) and places the knight in a central square, threatening at the same time the c2 pawn.

Now white has two options:

1. Qc4, which is a move that beginners would prefer as they cannot live without their queen. Black would reply with Nc2+ and after some moves here's how the position would look like:

```
[Variant "From Position"]
[FEN "r2qk2r/1p1bppbp/p1np2p1/4P2n/Q7/2N2N1P/PPP2PPB/R3KB1R w KQkq - 0 1"]

1. exd6 Nd4 2. Qc4 Nxc2+ 3. Kd1 Nxa1

```

Now White's position has multiple disadvantages:

* The centre is open and the white king can't castle!
    * Material difference
    * The rook and the bishops aren't fully activated compared to the respective Black pieces.
2. Qxd4, a move that more experienced players would prefer. Here's how the position would look like after Nc2+, etc:

```
[Variant "From Position"]
[FEN "r2qk2r/1p1bppbp/p1np2p1/4P2n/Q7/2N2N1P/PPP2PPB/R3KB1R w KQkq - 0 1"]

1. exd6 Nd4 2. Qxd4 Bxd4 3. Nxd4 O-O 4. O-O-O

```

Now White is **much** better as:

* They have castled.
    * Knights and the black-coloured bishop are active.
    * The white-coloured bishop will be developed probably in the next move, connecting the rooks at the same time.
    * They can attack the Black king (opposite castles)!
    * The dangerous black bishop on g7 is gone!
    * Bishop on d7 is inactive.

I believe you should try the move that will make your play easy later in the game and not Qxd4 just because the engine says so.
> 3 votes

---
Tags: puzzles, fork
---


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

Is there a way to do what I describe in Chess.com or perhaps another website/app?

# Answer
You can do this via Lichess:

1. Visit lichess and optionally create an account if you haven't done so.
2. Click Play with the computer.
3. Select "From Position" in the Variant field.
4. Insert the position FEN you want to play with the computer.
5. Choose a time control.
6. Choose the computer level. See this discussion for more info on what those mean.
7. Select a colour (White, Black or random).

Good luck!
> 12 votes

# Answer
You can also do this on chess.com.

1. Go to the "Learn" Tab
2. Click on "Analysis"
3. Setup your position via FEN or just by placing pieces
4. Click "Finish vs Computer"
> 17 votes

# Answer
Yes, you can do this in the chess.com app (or at least you could in a previous version.)

Tap the "Computer" menu button.

When it shows the starting options, tap "Position". (This is the bottom option; you may need to scroll down to see it.)

It gives you a list of choices. Tap "Custom Setup".

You can now set up the position as you like. Drag pieces around, add new ones from the bottom, or tap one to get rid of it. You can reset or clear the board from the menu icon. Tap the checkmark to finish setting up the position.

Set whatever other options you like, and start the game.
> 1 votes

---
Tags: computer-chess, chess.com
---


title: Elo distribution

text:
# Question
Title: Elo distribution
In some online chess platforms you can see the Elo distribution of the players. It usually has Gaussian form.

Is there somewhere where you can find the distribution of the classical Fide Elo?

# Answer
> 4 votes
As far as I know, Fide does not publish a figure of the Elo distribution. So you can plot it yourself from the latest rating list; or you can rely on secondary sources who occasionally post it, such the link provided by @Michael West or this answer on this site. Both show the distribution of Fide Elo on July 2014.

The figure below shows the Elo distribution on December 2020. As you can see, it doesn't follow a normal distribution, since there is a large number of low rated players (much greater number than in 2014).

# Answer
> 4 votes
Here are some fide visualizations from 2014. Distribution is one, but not the most interesting to me. Enjoy!

# Answer
> 3 votes
I've run some queries against my database constructed from the rating data downloaded from the the FIDE download site. I've then copied the output of the queries to Excel and asked it to draw some graphs.

Here are the results for standard, rapid and blitz for December 2020.

---
Tags: rating, fide, elo, statistics
---


title: Coordinates probem

text:
# Question
Title: Coordinates probem
```
[FEN "8/8/8/8/8/4R3/2N2R2/3N1k1K w - - 0 1"]

```

Given that this position could be reached in a legal game of chess, and that no piece was captured on the last move, are we seeing the board from White's or Black's side?

# Answer
> 2 votes
Answer:

> Black's side.

Reasoning:

> For convenience I'll just use white coordinates. If no capture was made last move, the rook cannot come from the f-file, and the black king was the only black piece on the board. Where did the black king come from previously? Not from g1/g2 (next to the white king), not from e2 (impossible double check from both rooks), and not from e1 (impossible double check from e3 rook + c2 knight).

> So the black king must have come from "f2", and the double check from the rook + knight is settled with an unpromotion. Board is from black's perspective; retract -1. Re7 Kc7 -2. dxe8=N and the position unlocks.

---
Tags: problems, retrograde-analysis
---


# Question
Title: In this position why shouldn't the knight capture the rook?
The white knight is going to move to e6. However, the computer advises the rook to capture the pawn in b2. Even after the knight moves to e6, forking the queen and the rook, it advises to NOT capture either and instead go for the pawn c5 (see 2nd picture). Why is it a better move?

next moves from the analysis tab: (Nxe6, Qd7, Nxc5)  and later

# Answer
Black's idea is to play Re2+ at the right moment. If, for instance, White takes the rook with 19.Nxf8 Kxf8, there is no way to prevent Black from playing Re2+ later, winning the Queen (after Qxe2 Bxe2 Kxe2, not hopeless but slightly good for Black possibly; in practice Black might pick up g2 before doing this), reason being that Kf1 walks into a discovered attack. Because of that, White chooses to play 19.Nxc5 instead to capture the bishop on a6 and thereby prevent Re2+.

Although the difference between taking the rook or going for the bishop is not that big, both moves can be considered reasonable.

EDIT: In fact a deeper analysis reveals that taking the rook is in fact to be preferred since after 19.Nxc5 Qc6 20.Nxa6 d4! apparently leads to an advantage for Black, threatening Qxg2 and thus forcing 21.Qf3 after which Qxa6 now leads to a Black advantage due to having forced the enemy queen away from the Queen side defenses. So I suppose you were right after all to consider 19.Nxf8 stronger.
> 7 votes

---
Tags: analysis, problems
---


# Question
Title: Iterative deepening: what should I do with previous results?
I implemented a negamax with alpha beta and aspiration windows. Now, it also has iterative deepening. When I let the engine run for 15 seconds in the below position, it finds a move at depth 2 with very good value (135/ d8-d7). But when it goes one depth deeper, the movie is bad because it loses the queen (980). Looking at the best move at the deepest depth, when it fully searches, I get f7-f6 with an evaluation of 200 and it is a way better move.

Do I just throw away the best move of a previously searched depth, and only look at the deepest fully searched depth? My brain somehow can't find the solution.

```
[FEN "rnbqkbnr/5ppp/4p3/2PN2B1/1P2P3/p4N2/P1P1BPPP/1R1QK2R b Kkq - 0 1"]

```

# Answer
In alpha/beta pruning, the order that moves are searched in matters a great deal. You always want the best move(s) to be searched first--this creates more beta cutoffs. The basic idea is that before searching each level of the tree, we will sort the moves based on how good they are, then search the moves *in that order*.

Of course, this is quasi-paradoxical ("how to find the best move: step 1, find the best move...") and *one of* the ways we get around that is using iterative deepening. Search the position at a smaller depth, then put that move at the very top of the list for the next iteration. This is the point of iterative deepening.

---

Because you are just starting out, (and are searching depth 2 in 15 sec), I'd really recommend

1. making sure your alpha/beta is bug free (for the love of god, use negamax)
2. implementing other move ordering techniques before iterative deepening.
3. implementing null move pruning

These last two are (relatively) easy to do, and give essentially free speedups.
> 2 votes

---
Tags: engines, software
---